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10.1007/s00426-019-01250-x

Psychological research

Psychol Res

Investigating limits of task prioritization in dual-tasking: evidence from the prioritized processing and the psychological refractory period paradigms.

Dual-tasking often requires prioritizing one task over the other. For example, in the psychological refractory period (PRP) paradigm, participants are instructed to initially respond to Task 1 (T1) and only then to Task 2 (T2). Furthermore, in the prioritized processing paradigm (PP), participants are instructed to perform T2 only if T1 was a no-go trial-requiring even more prioritization. The present study investigated the limits of task prioritization. Two experiments compared performance in the PRP paradigm and the PP paradigm. To manipulate task prioritization, tasks were rewarded differently (e.g., high reward for T1, low reward for T2, and vice versa). We hypothesized (a) that performance will improve for the highly rewarded task (Experiments 1 and 2) and (b) that there are stronger reward effects for T1 in the PRP than in the PP paradigm (Experiment 2). Results showed an influence of reward on task prioritization: For T1, high reward (compared to low reward) caused a speed-up of responses that did not differ between the two paradigms. However, for T2, reward influenced response speed selectively in the PP paradigm, but not in the PRP paradigm. Based on paradigm-specific response demands, we propose that the coordination of two motor responses plays a crucial role in prioritizing tasks and might limit the flexibility of the allocation of preparatory capacity.

CognitiveTask

PRP

10.1037/xhp0000674

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Dual-task interference on left eye utilization during facial emotion perception.

There is an ongoing debate in the literature about whether facial emotion perception is carried automatically-that is, without effort or attentional resources. While it is generally accepted that spatial attention is necessary for the perception of emotional facial expressions, the picture is less clear for central attention. Using the bubbles method, we provide results that were obtained by measuring the effect of the psychological refractory period on diagnostic information for the basic facial expressions. Based on previous findings that linked spatial attention with processing of the eyes and of high spatial frequencies in the visual periphery, we hypothesized that reliance on the eyes might decrease when central resources were monopolized by a difficult prioritized auditory task. Central load led to a marked decrease in left eye utilization that was generalized across emotions; on the contrary, utilization of the mouth was unaffected by central load. Thus, processing of the left eye might be nonautomatic, and processing of the mouth might be automatic. Interestingly, we also observed a reduction in reliance on the left side of the face under central load that was accompanied by a commensurate increase in reliance on the right side of the face. We end with a discussion of how hemispheric asymmetries might account for these peculiar findings. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

CognitiveTask

PRP

10.1371/journal.pone.0199084

PloS one

PLoS One

Attentional modulation of orthographic neighborhood effects during reading: Evidence from event-related brain potentials in a psychological refractory period paradigm.

It is often assumed that word reading proceeds automatically. Here, we tested this assumption by recording event-related potentials during a psychological refractory period (PRP) paradigm, requiring lexical decisions about written words. Specifically, we selected words differing in their orthographic neighborhood size-the number of words that can be obtained from a target by exchanging a single letter-and investigated how influences of this variable depend on the availability of central attention. As expected, when attentional resources for lexical decisions were unconstrained, words with many orthographic neighbors elicited larger N400 amplitudes than those with few neighbors. However, under conditions of high temporal overlap with a high priority primary task, the N400 effect was not statistically different from zero. This finding indicates strong attentional influences on processes sensitive to orthographic neighbors during word reading, providing novel evidence against the full automaticity of processes involved in word reading. Furthermore, in conjunction with the observation of an underadditive interaction between stimulus onset asynchrony (SOA) and orthographic neighborhood size in lexical decision performance, commonly taken to indicate automaticity, our results raise issues concerning the standard logic of cognitive slack in the PRP paradigm.

CognitiveTask

PRP

10.3758/s13414-018-01660-w

Attention, perception & psychophysics

Atten Percept Psychophys

Action scheduling in multitasking: A multi-phase framework of response-order control.

Temporal organization of human behavior is particularly important when several action requirements must be processed around the same time. A crucial challenge in such multitasking situations is to control the temporal response order. However, multitasking studies usually focus on temporal processing dynamics after a specific response order - which is usually triggered by stimulus sequence and instructions - has been determined, whereas a comprehensive study of response-order scheduling mechanisms is still lacking. Across three psychological refractory period (PRP) experiments, we examined the impact of stimulus order, response characteristics, and several other factors on response order. Crucially, we utilized a combination of effector systems (oculomotor and manual) that are known to ensure reasonable response order variability in the first place. The results suggest that - contrary to previous assumptions - bottom-up factors (e.g., stimulus order) are not the primary determinant of temporal action scheduling. Instead, we found a major influence of effector-based characteristics (i.e., oculomotor task prioritization) that could be attenuated by both instructions and changes in the task environment (providing temporally predictable input). Effects of between-task compatibility suggest that a dedicated stimulus-code comparison process precedes and affects response-order scheduling. Based on the present results and previous findings, we propose a multi-phase framework of temporal response-order control that emphasizes the extent to which cognitive control of action scheduling is dynamically adaptive to particular task characteristics.

CognitiveTask

PRP

10.1016/j.cortex.2018.10.023

Cortex; a journal devoted to the study of the nervous system and behavior

Cortex

Using the locus of slack logic to determine whether the output form of inhibition of return affects an early or late stage of processing.

Slower reaction times to targets presented at a previously cued or attended location are often attributed to inhibition of return (IOR). It has been suggested that IOR affects a process at the output end of processing continuum when it is generated while the oculomotor system is activated. Following the path set by Kavyani, Farsi, Abdoli, and Klein (2017) we used the locus of slack logic embedded in the psychological refractory period (PRP) paradigm to test this idea. We generated what we expected would be the output form of IOR by beginning each with participants making a target directed saccade which was followed by two tasks. Task 1, was a 2-choice auditory discrimination task and Task 2 was a 2-choice visual localization task. We varied the interval between the onsets of the two targets associated with these two tasks (using TTOAs of 200, 400, or 800 msec). As expected the visual task suffered from a robust PRP effect (substantially delayed RTs at the shorter TTOAs). There was also a robust IOR effect with RTs to localize visual targets being slower when the targets were presented at a previously fixated location. Importantly, and in striking to our previous results wherein we generated the input form of IOR, in the present study there was an additive effect between IOR and TTOA on RT2. As implied by the locus of slack logic, we therefore conclude that the form of IOR generated when the oculomotor system is activated affects a late stage of processing. Converging evidence for this conclusion, from a variety of neuroscientific methods, is presented and the dearth of such evidence about the input form of IOR is noted.

CognitiveTask

PRP

10.3389/fpsyg.2018.01942

Frontiers in psychology

Front Psychol

Dual-Tasking in the Near-Hand Space: Effects of Stimulus-Hand Proximity on Between-Task Shifts in the Psychological Refractory Period Paradigm.

Two decades of research indicate that visual processing is typically enhanced for items that are in the space near the hands (near-hand space). Enhanced attention and cognitive control have been thought to be responsible for the observed effects, amongst others. As accumulating experimental evidence and recent theories of dual-tasking suggest an involvement of cognitive control and attentional processes during dual tasking, dual-task performance may be modulated in the near-hand space. Therefore, we performed a series of three experiments that aimed to test if the near-hand space affects the shift between task-component processing in two visual-manual tasks. We applied a Psychological Refractory Period Paradigm (PRP) with varying stimulus-onset asynchrony (SOA) and manipulated stimulus-hand proximity by placing hands either on the side of a computer screen (near-hand condition) or on the lap (far-hand condition). In Experiment 1, Task 1 was a number categorization task (odd vs. even) and Task 2 was a letter categorization task (vowel vs. consonant). Stimulus presentation was spatially segregated with Stimulus 1 presented on the right side of the screen, appearing first and then Stimulus 2, presented on the left side of the screen, appearing second. In Experiment 2, we replaced Task 2 with a color categorization task (orange vs. blue). In Experiment 3, Stimulus 1 and Stimulus 2 were centrally presented as a single bivalent stimulus. The classic PRP effect was shown in all three experiments, with Task 2 performance declining at short SOA while Task 1 performance being relatively unaffected by task-overlap. In none of the three experiments did stimulus-hand proximity affect the size of the PRP effect. Our results indicate that the switching operation between two tasks in the PRP paradigm is neither optimized nor disturbed by being processed in near-hand space.

CognitiveTask

PRP

10.1037/xhp0000576

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Practice-related optimization of dual-task performance: Efficient task instantiation during overlapping task processing.

We compared the effects of extended dual-task practice in a task situation of the psychological refractory period (PRP) type with the effects of single-task practice. The experiments tested the assumption that performance of Task 2 in the PRP task improves more rapidly with dual-task practice than with single-task practice, which points to a preponed instantiation of Task 2 during dual-task processing in working memory and to the acquisition of dual-task coordination skills. Experiments 1 and 2 showed that such dual-task coordination skills can be acquired under conditions of less-complex tasks with no more than four stimulus-response mappings in Task 2, independently on the compatibility of the mappings. Experiment 3 showed no evidence for the acquisition of dual-task coordination skills under condition of eight stimulus-response mappings in Task 2. This indicates that the working memory load exposed by the number of stimulus-response mappings is a critical parameter limiting the degree to which participants can prepone the conjoint instantiation of two task sets during dual-task processing. The findings specify a model assuming the conjoint and efficient initiation of task sets in working memory as a result of extended dual-task practice. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

CognitiveTask

PRP

10.1016/j.actpsy.2018.09.006

Acta psychologica

Acta Psychol (Amst)

Dual-tasking with simple linguistic tasks: Evidence for serial processing.

In contrast to the large amount of dual-task research investigating the coordination of a linguistic and a non-linguistic task, little research has investigated how two linguistic tasks are coordinated. However, such research would greatly contribute to our understanding of how interlocutors combine speech planning and listening in conversation. In three dual-task experiments we studied how participants coordinated the processing of an auditory stimulus (S1), which was either a syllable or a tone, with selecting a name for a picture (S2). Two SOAs, of 0 ms and 1000 ms, were used. To vary the time required for lexical selection and to determine when lexical selection took place, the pictures were presented with categorically related or unrelated distractor words. In Experiment 1 participants responded overtly to both stimuli. In Experiments 2 and 3, S1 was not responded to overtly, but determined how to respond to S2, by naming the picture or reading the distractor aloud. Experiment 1 yielded additive effects of SOA and distractor type on the picture naming latencies. The presence of semantic interference at both SOAs indicated that lexical selection occurred after response selection for S1. With respect to the coordination of S1 and S2 processing, Experiments 2 and 3 yielded inconclusive results. In all experiments, syllables interfered more with picture naming than tones. This is likely because the syllables activated phonological representations also implicated in picture naming. The theoretical and methodological implications of the findings are discussed.

CognitiveTask

PRP

10.5709/acp-0239-y

Advances in cognitive psychology

Adv Cogn Psychol

Common Cognitive Control Processes Underlying Performance in Task-Switching and Dual-Task Contexts.

In the present study, participants performed highly comparable task-switching and dual-task paradigms, and the paradigm-specific performance costs were analysed in the context of the commonly postulated core components of cognitive control (i.e., working memory updating, inhibition, and shifting). In the task-switching paradigm, we found switch costs (i.e., switch trials vs. repetition trials) and mixing costs (i.e., repetition trials in mixed-task blocks vs. single-task trials). In the dual-task paradigm, we observed a psychological refractory period (PRP) effect (i.e., Task 2 [T2] performance after short stimulus-onset asynchrony [SOA] vs. long SOA), dual-task costs (i.e., T2 dual-task performance with a long SOA in trials with a task repetition between Task 1 [T1] and T2 vs. single-task performance), and switch costs in T2 (i.e., dual-task performance in trials with a switch between T1 and T2 vs. dual-task performance in trials with a repetition between T1 and T2). A within-subjects comparison of the performance costs showed a correlation between mixing costs and dual-task costs, possibly indicating shared underlying cognitive control processes in terms of working memory updating. Surprisingly, there was also a correlation between switch costs and the PRP effect, presumably suggesting that cognitive control, as opposed to passive queuing of response selection processes, contributes to the PRP effect.

CognitiveTask

PRP

10.1016/j.neuropsychologia.2018.09.003

Neuropsychologia

Neuropsychologia

Multitasking in aging: ERP correlates of dual-task costs in young versus low, intermediate, and high performing older adults.

With large inter-individual variability, older adults show a decline in cognitive performance in dual-task situations. Differences in attentional processes, working memory, response selection, and general speed of information processing have been discussed as potential sources of this decline and its between-subject variability. In comparison to young subjects (n = 36, mean age: 25 years), we analyzed the performance of a large group of healthy elderly subjects (n = 138, mean age: 70 years) in a conflicting dual-task situation (PRP paradigm). Based on their dual-task costs (DTCs), the older participants were clustered in three groups of high, medium, and low performing elderly. DTCs differed between groups and increased linearly from young subjects to low performing elderly. The groups did not differ with respect to ERP-components related to task preparation (CNV) and recall of stimulus-response mappings (P2). Peak latencies of the frontocentral P2 and N2 were shorter in young as compared to older adults but did not differ between elderly performance groups. However, differences in N2 amplitude between short and long SOA were correlated with the corresponding DTCs, suggesting more efficient S-R implementation in subjects with lower DTCs. Based on our results, between-subject differences in dual-task interference can be explained in terms of individual differences in selection of an appropriate response in dual-task situations.

CognitiveTask

PRP

10.1007/s00221-018-5369-1

Experimental brain research

Exp Brain Res

Keeping your eye on the target: eye-hand coordination in a repetitive Fitts' task.

In a cyclical Fitts' task, hand movements transition from continuous to discrete movements when the Index of Difficulty (ID) increases. Moreover, at high ID (small target), the eyes saccade to and subsequently fixate the targets at every movement, while at low ID (large target) intermittent monitoring is used. By hypothesis, the (periodic) gaze shifts are abandoned for movement times shorter than about 0.350 s due to systemic constraints (i.e., a refractory period and intrinsic latency). If so, the transition in eye and hand movements is independent. To investigate these issues, the present study examined the effects of changing ID via the targets' width or distance as well as hysteresis in eye-hand coordination. To this aim, 14 participants performed a cyclical Fitts' task while their hand and eye movements were recorded simultaneously. The results show that the transition in eye-hand synchronization (at 2.87 bit; 0.25 s) and in hand dynamics (at 4.85 bit; 0.81 s) neither co-occurred nor correlated. Some small width vs. distance dissociations and hysteresis effects were found, but they disappeared when eye-hand synchronization was viewed as a function of movement time rather than ID. This confirms that a minimal between-saccade time is the limiting factor in eye-hand synchronization. Additionally, the timing between the start of the hand movement and the saccade appeared to be relatively constant (at 0.15 s) and independent of movement time, implying a constant delay that should be implemented in a dynamical model of eye-hand coordination.

CognitiveTask

PRP

10.1037/xlm0000635

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Introspection is not always blind to the costs of multitasking: The case of task switching.

Previous studies have provided evidence that introspection about dual-task performance in the psychological refractory period (PRP) paradigm is severely limited. The present study investigated introspection at the other pole of the multitasking continuum, namely task switching. In 2 experiments, participants provided estimates of their response times (i.e., introspective RTs) after each trial in modified versions of the alternating-runs and the task-cuing paradigm, which included only 2 tasks in a trial. In contrast to the previously observed unawareness of dual-task costs in the PRP paradigm, participants reported their switch costs in introspective RTs. Thus, introspection about multitasking performance appears to not always be as limited as in the PRP paradigm. Nevertheless, introspection is not without limits also in task switching. Participants only partly reported the beneficial impact of longer preparation time on their performance. The present results suggest that introspective RTs depend on multiple cues, of which some are valid and some are invalid. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

CognitiveTask

PRP

10.4103/0366-6999.238144

Chinese medical journal

Chin Med J (Engl)

Visual Dominance Effect upon Passing the Central Bottleneck of Information Processing.

In the classical psychological refractory period (PRP) paradigm, two stimuli are presented in brief succession, and participants are asked to make separate speeded responses to both stimuli. Due to a central cognitive bottleneck, responses to the second stimulus are delayed, especially at short stimulus-onset asynchrony (SOA) between the two stimuli. Although the mechanisms of dual-task interference in the classical PRP paradigm have been extensively investigated, specific mechanisms underlying the cross-modal PRP paradigm are not well understood. In particular, it remains unknown whether the dominance of vision over audition manifests in the cross-modal PRP tasks. The present study aimed to investigate whether the visual dominance effect manifests in the cross-modal PRP paradigm. We adapted the classical PRP paradigm by manipulating the order of a visual and an auditory task: the visual task could either precede the auditory task or vice versa, at either short or long SOAs. Twenty-five healthy participants took part in Experiment 1, and thirty-three new participants took part in Experiment 2. Reaction time and accuracy data were calculated and further analyzed by repeated-measures analysis of variance. The results showed that visual precedence in the Visual-Auditory condition caused larger impairments to the subsequent auditory processing than vice versa in the Auditory-Visual condition: a larger delay of second response was revealed in the Visual-Auditory condition (135 ± 10 ms) than the Auditory-Visual condition (88 ± 9 ms). This effect was found only at the short SOAs under the existence of the central bottleneck, but not at the long SOAs. Moreover, this effect occurred both when the single visual and the single auditory task were of equal difficulty in Experiment 1 and when the single auditory task was more difficult than the single visual task in Experiment 2. Results of the two experiments suggested that the visual dominance effect occurred under the central bottleneck of cognitive processing.

CognitiveTask

PRP

10.3389/fpsyg.2018.01031

Frontiers in psychology

Front Psychol

Dual-Task Processing With Identical Stimulus and Response Sets: Assessing the Importance of Task Representation in Dual-Task Interference.

Limitations in our ability to produce two responses at the same time - that is, dual-task interference - are typically measured by comparing performance when two stimuli are presented and two responses are made in close temporal proximity to when a single stimulus is presented and a single response is made. While straightforward, this approach leaves open multiple possible sources for observed differences. For example, on dual-task trials, it is typically necessary to identify two stimuli nearly simultaneously, whereas on typical single-task trials, only one stimulus is presented at a time. These processes are different from selecting and producing two distinct responses and complicate the interpretation of dual- and single-task performance differences. Ideally, performance when two tasks are executed should be compared to conditions in which only a single task is executed, while holding constant all other stimuli, response, and control processing. We introduce an alternative dual-task procedure designed to approach this ideal. It holds stimulus processing constant while manipulating the number of "tasks." Participants produced unimanual or bimanual responses to pairs of stimuli. For one set of stimuli (two-task set), the mappings were organized so an image of a face and a building were mapped to particular responses (including no response) on the left or right hands. For the other set of stimuli (one-task set), the stimuli indicated the same set of responses, but there was not a one-to-one mapping between the individual stimuli and responses. Instead, each stimulus pair had to be considered together to determine the appropriate unimanual or bimanual response. While the stimulus pairs were highly similar and the responses identical across the two conditions, performance was strikingly different. For the two-task set condition, bimanual responses were made more slowly than unimanual responses, reflecting typical dual-task interference, whereas for the one-task set, unimanual responses were made more slowly than bimanual. These findings indicate that dual-task costs occur, at least in part, because of the interfering effects of task representation rather than simply the additional stimulus, response, or other processing typically required on dual-task trials.

CognitiveTask

PRP

10.3758/s13414-018-1541-8

Attention, perception & psychophysics

Atten Percept Psychophys

Processing order in dual-task situations: The "first-come, first-served" principle and the impact of task order instructions.

When two overlapping tasks are processed, they hit a bottleneck at a central processing stage that prevents simultaneous processing of the two tasks. Thus far, however, the factors determining the processing order of the tasks at the bottleneck are unknown. The present study was designed to (re)investigate whether the arrival times of the two tasks at the central bottleneck are a key determinant of the processing order (cf. Sigman & Dehaene, 2006). To this end, we implemented a visual-auditory dual task with a random stimulus order, in which we manipulated arrival time by prolonging the initial, perceptual processing stage (stimulus analysis) of the visual task and compared the effects of this manipulation with those of one impacting the central bottleneck stage of the visual task. Additionally, we implemented two instruction conditions: Participants were told to respond either in the order of stimulus presentation or in the order they preferred. The manipulation of the visual perception stage led to an increase in task response reversals (i.e., the response order was different from the order of stimulus presentation), whereas there was no such increase when the bottleneck stage was manipulated. This pattern provides conclusive evidence that the processing order at the bottleneck is (at least in part) determined by the arrival times of the tasks at that point. Reaction time differences between the two instruction conditions indicated that additional control processes are engaged in determining task processing order when the participants are expressly told to respond in the order of stimulus presentation.

CognitiveTask

PRP

10.3758/s13423-018-1498-6

Psychonomic bulletin & review

Psychon Bull Rev

The bottleneck of the psychological refractory period effect involves timing of response initiation rather than response selection.

The Psychological Refractory Period (PRP) effect is a delay in responding that is assumed to be caused by a bottleneck that prevents preparation of a second action until preparation of the previous action has been completed. The bottleneck is usually attributed to a limitation that prevents concurrent selection of two responses. However, evidence reviewed here challenges this selection interpretation. We propose instead that the bottleneck is due to a process that programs the timing of response initiation, and which must be completed immediately prior to responding. This hypothesis is based on two conclusions from recent developments in research, which includes findings from paradigms that do not involve the PRP. The first conclusion is from studies involving the startle response and single-task simple (precued) reaction time; these studies indicate that programming the timing of response onsets is needed to enable response initiation. This programing takes longer for more complicated timing, and must be delayed until just prior to responding. The second conclusion is from studies of concurrent rhythmic movements demonstrating that the representation of timing is restricted to one temporal frame unless very rapid performance enables parallel timing. These findings reveal limitations that can combine to produce the PRP bottleneck. This interpretation clarifies otherwise puzzling aspects of the PRP effect and indicates that a fundamental restriction concerning response timing may underlie both limitations and the PRP effect that they produce. This restriction might arise because timing is controlled by subcortical neural structures with limited working memory.

CognitiveTask

PRP

10.1177/1747021818778970

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

The central locus of self-prioritisation.

Self-related information is under many circumstances processed in a preferred and biased way, leading to what has been termed the self-prioritisation effect (SPE). The SPE has been demonstrated with arbitrary stimuli assigned to self and others, thereby controlling the influence of familiarity, and originally been attributed to facilitated perceptual processing of self-related stimuli. Subsequent studies, however, casted doubts on this interpretation and suggested further possible sources for the SPE. In the present four experiments, we used the well-established psychological refractory period paradigm together with the locus of slack and the effect propagation logic to pinpoint the source of the SPE. The data consistently demonstrated the SPE across all experiments. More important, the results converge on the notion that the SPE has its source in a capacity-limited stage of central processing. The implications of these results are discussed in light of possible candidate processes as sources for the SPE, such as memory-related processing.

CognitiveTask

PRP

10.1037/xlm0000565

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

The motor locus of no-go backward crosstalk.

A frequent observation in dual-task studies is the backward crosstalk effect (BCE), meaning that aspects of a secondary Task 2 influence Task 1 performance. Up to this point, 2 major types of the BCE were investigated: a BCE based on dimensional overlap between both stimuli and/or responses (the compatibility-based BCE), and a BCE based on whether Task 2 is a go or no-go task (the no-go BCE). Recent evidence suggests that the compatibility-based BCE has its locus inside the response selection stage. The available evidence for the locus of the no-go BCE is still mixed, however. To this end, the 3 experiments reported in the present study used an extended psychological refractory period (PRP) paradigm with 3 subsequent tasks. Applying the locus of slack logic in Experiment 1, the no-go BCE was not absorbed into the cognitive slack and, thus, a locus before response selection could be ruled out. Subsequently applying the effect propagation logic in Experiment 2 and 3, the no-go BCE arising in Task 1 was even inverted in Task 3. Because no propagation of the no-go BCE was observed, a locus before or in response selection could be ruled out. Thus, we conclude that the no-go BCE has its locus during motor execution. Because the no-go BCE and the compatibility-based BCE are located in different stages, we suggest that both types of the BCE do not share a common underlying mechanism. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

CognitiveTask

PRP

10.1016/j.neuropsychologia.2018.04.014

Neuropsychologia

Neuropsychologia

Preparatory brain activity in dual-tasking.

Task preparation in dual-tasking is more complex than preparation for single tasks and involves additional factors such as task prioritization. Utilizing event-related potentials, we sought to disentangle preparatory processes involving preparation on the subtask level and the superordinate dual-task level. Participants worked on a psychological refractory period paradigm in which two temporally overlapping tasks have to be completed in a specified order. Whereas dual-task-related preparation was measured by comparing task-order switches and repetitions, subtask preparation was isolated through error precursors for the individual subtasks. We found that a switch-related posterior positivity was linked to the preparation of the superordinate dual-task set. In contrast, an early frontal modulation and a stimulus-preceding negativity were markers of subtask preparation of Task 1 and Task 2, respectively. Our study provides neural evidence for a hierarchical system of control processes in dual-tasking and confirms assumptions from earlier behavioral and computational studies on strategic task prioritization.

CognitiveTask

PRP

10.5334/joc.21

Journal of cognition

J Cogn

On the Automaticity of Familiarity in Short-term Recognition: A Test of the Dual-Process Assumption with the PRP Paradigm.

Dual-process models of recognition often assume that one retrieval process, generating a familiarity signal, is automatic, whereas the other, recollection, is controlled. Four experiments are presented to test for automaticity of familiarity in a short-term recognition task. The experiments use the Psychological Refractory Period (PRP) paradigm to assess whether familiarity requires central processing capacity. Task 1 was an oral tone-classification task. Task 2 was a local-recognition task, in which participants decided whether a probe matched a particular item in the memory set, identified by its screen location. Intrusion probes, matching an item of the memory set in a different location, were slower and more difficult to reject than new probes. The size of this intrusion cost reflects the influence of familiarity on recognition. In all four experiments the size of the intrusion cost was additive with the stimulus-onset-asynchrony (SOA) of Task 1 and Task 2, demonstrating that extraction of familiarity requires central capacity. In addition, Experiment 2 showed additive effects of memory set size and serial position with SOA, confirming that recollection, too, requires central capacity. Experiments 3A and 3B compared a condition including new probes to one including only positive and intrusion probes; in the latter condition the familiarity signal was completely uninformative. Participants showed some ability to reduce the influence of familiarity when it was completely uninformative, but only when they were explicitly told to do so (Experiment 3B). To conclude, by one criterion familiarity is a controlled process: It demands central processing capacity. It might also be controlled by another criterion: People can intentionally reduce the influence of familiarity on recognition decision, but they fail to do so spontaneously even when it would be advantageous. All raw data are available on the Open Science Framework: osf.io/7pr72.

CognitiveTask

PRP

10.3389/fnhum.2018.00024

Frontiers in human neuroscience

Front Hum Neurosci

Dual-Tasking in Multiple Sclerosis - Implications for a Cognitive Screening Instrument.

The monitoring of cognitive functions is central to the assessment and consecutive management of multiple sclerosis (MS). Though, especially cognitive processes that are central to everyday behavior like dual-tasking are often neglected. We examined dual-task performance using a psychological-refractory period (PRP) task in = 21 patients and healthy controls and conducted standard neuropsychological tests. In dual-tasking, MS patients committed more erroneous responses when dual-tasking was difficult. In easier conditions, performance of MS patients did not differ to controls. Interestingly, the response times were generally not affected by the difficulty of the dual task, showing that the deficits observed do not reflect simple motor deficits or deficits in information processing speed but point out deficits in executive control functions and response selection in particular. Effect sizes were considerably large with ∼0.80 in mild affected patients and the achieved power was above 99%. There are cognitive control and dual tasking deficits in MS that are not attributable to simple motor speed deficits. Scaling of the difficulty of dual-tasking makes the test applied suitable for a wide variety of MS-patients and may complement neuropsychological assessments in clinical care and research setting.

CognitiveTask

PRP

10.3758/s13414-017-1469-4

Attention, perception & psychophysics

Atten Percept Psychophys

Dual-task automatization: The key role of sensory-motor modality compatibility.

How do people automatize their dual-task performance through bottleneck bypassing (i.e., accomplish parallel processing of the central stages of two tasks)? In the present work we addressed this question, evaluating the impact of sensory-motor modality compatibility-the similarity in modality between the stimulus and the consequences of the response. We hypothesized that incompatible sensory-motor modalities (e.g., visual-vocal) create conflicts within modality-specific working memory subsystems, and therefore predicted that tasks producing such conflicts would be performed less automatically after practice. To probe for automaticity, we used a transfer psychological refractory period (PRP) procedure: Participants were first trained on a visual task (Exp. 1) or an auditory task (Exp. 2) by itself, which was later presented as Task 2, along with an unpracticed Task 1. The Task 1-Task 2 sensory-motor modality pairings were either compatible (visual-manual and auditory-vocal) or incompatible (visual-vocal and auditory-manual). In both experiments we found converging indicators of bottleneck bypassing (small dual-task interference and a high rate of response reversals) for compatible sensory-motor modalities, but indicators of bottlenecking (large dual-task interference and few response reversals) for incompatible sensory-motor modalities. Relatedly, the proportion of individuals able to bypass the bottleneck was high for compatible modalities but very low for incompatible modalities. We propose that dual-task automatization is within reach when the tasks rely on codes that do not compete within a working memory subsystem.

CognitiveTask

PRP

10.3758/s13414-017-1442-2

Attention, perception & psychophysics

Atten Percept Psychophys

The cognitive loci of the display and task-relevant set size effects on distractor interference: Evidence from a dual-task paradigm.

The congruency effect of a task-irrelevant distractor has been found to be modulated by task-relevant set size and display set size. The present study used a psychological refractory period (PRP) paradigm to examine the cognitive loci of the display set size effect (dilution effect) and the task-relevant set size effect (perceptual load effect) on distractor interference. A tone discrimination task (Task 1), in which a response was made to the pitch of the target tone, was followed by a letter discrimination task (Task 2) in which different types of visual target display were used. In Experiment 1, in which display set size was manipulated to examine the nature of the display set size effect on distractor interference in Task 2, the modulation of the congruency effect by display set size was observed at both short and long stimulus-onset asynchronies (SOAs), indicating that the display set size effect occurred after the target was selected for processing in the focused attention stage. In Experiment 2, in which task-relevant set size was manipulated to examine the nature of the task-relevant set size effect on distractor interference in Task 2, the effects of task-relevant set size increased with SOA, suggesting that the target selection efficiency in the preattentive stage was impaired with increasing task-relevant set size. These results suggest that display set size and task-relevant set size modulate distractor processing in different ways.

CognitiveTask

PRP

10.1037/xlm0000474

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Effect monitoring in dual-task performance.

Actions aim to produce effects in the environment. To accomplish this properly, we not only have to recruit the appropriate motor patterns, but also we must be able to monitor whether an intended effect has ultimately been realized. Here, we investigated the impact of such effect monitoring on performance in multitasking situations: Multitasking basically means to produce and monitor multiple actions and effects in fast succession. We show that effect monitoring cannot run in parallel, without causing processing decrements, with a second task. Also, monitoring of effects that are spatially incompatible to a response seems to take longer than the monitoring of spatially compatible action effects (Experiments 1 through 4). We further argue that effect monitoring is essential toward learning of response-effect associations, as it captures not only anticipated action effects, but also unpredictable occurrences in the environment (Experiments 5a and 5b). (PsycINFO Database Record

CognitiveTask

PRP

10.3758/s13423-017-1386-5

Psychonomic bulletin & review

Psychon Bull Rev

Localizing semantic interference from distractor sounds in picture naming: A dual-task study.

In this study we explored the locus of semantic interference in a novel picture-sound interference task in which participants name pictures while ignoring environmental distractor sounds. In a previous study using this task (Mädebach, Wöhner, Kieseler, & Jescheniak, in Journal of Experimental Psychology: Human Perception and Performance, 43, 1629-1646, 2017), we showed that semantically related distractor sounds (e.g., BARKING) interfere with a picture-naming response (e.g., "horse") more strongly than unrelated distractor sounds do (e.g., DRUMMING). In the experiment reported here, we employed the psychological refractory period (PRP) approach to explore the locus of this effect. We combined a geometric form classification task (square vs. circle; Task 1) with the picture-sound interference task (Task 2). The stimulus onset asynchrony (SOA) between the tasks was systematically varied (0 vs. 500 ms). There were three central findings. First, the semantic interference effect from distractor sounds was replicated. Second, picture naming (in Task 2) was slower with the short than with the long task SOA. Third, both effects were additive-that is, the semantic interference effects were of similar magnitude at both task SOAs. This suggests that the interference arises during response selection or later stages, not during early perceptual processing. This finding corroborates the theory that semantic interference from distractor sounds reflects a competitive selection mechanism in word production.

CognitiveTask

PRP

10.1027/1618-3169/a000369

Experimental psychology

Exp Psychol

How Social and Refractory Is the Social Psychological Refractory Period?

The social psychological refractory period (PRP) effect refers to an increase in RT to the second of two successive stimuli when another person responds to the first stimulus (shared dual-task condition) rather than when a single person responds to both stimuli (individual dual-task condition). We investigated (a) whether a social PRP effect would occur without explicit instruction concerning task priority and (b) whether there are crosstalk effects in the shared dual-task situation. We observed a strong PRP effect together with a small crosstalk effect in the individual dual-task condition, but in the shared dual-task condition both effects were absent. These findings suggest that the explicit instruction to perform responses in a fixed order is necessary to obtain the social PRP effect. In the individual dual-task condition, sequential processing can be seen as a means to reduce or prevent crosstalk effects, which is not necessary in the shared dual-task condition.

CognitiveTask

PRP

10.1007/s00426-017-0874-6

Psychological research

Psychol Res

The role of feedback delay in dual-task performance.

Doing two things at once is hard, and it is probably hard for various reasons. Here we aim to demonstrate that one so far barely considered reason is the monitoring of sensory action feedback, which detracts from processing of other concurrent tasks. To demonstrate this, we engaged participants in a psychological refractory period paradigm. The responses in the two tasks produced visual action effects. These effects occurred either immediately or they were delayed for the first of the two responses. We assumed that delaying these effects would engage a process of monitoring visual feedback longer, and delay a concurrent task more, as compared to immediate effects. This prediction was confirmed in two experiments. We discuss the reasons for feedback monitoring and its possible contribution to dual tasking.

CognitiveTask

PRP

10.1037/xhp0000445

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Identifying the locus of compatibility-based backward crosstalk: Evidence from an extended PRP paradigm.

The backward crosstalk effect (BCE) in dual tasking means that characteristics of Task 2 of 2 subsequently performed tasks influence Task 1 performance. This observation indicates that certain features of the second response are already activated to some degree before the first response is selected. Therefore, the BCE challenges bottleneck models, which assume that Task 2 response selection does not begin until Task 1 response selection is finished. Instead, an extended model with a capacity-unlimited response activation stage prior to the bottleneck as the locus of the BCE was suggested. To determine the exact locus of the BCE within the stages of task processing, 5 experiments were carried out. Experiments 1 to 4 were psychological refractory period-like experiments with 3 subsequent tasks. A prebottleneck locus of the BCE was ruled out in Experiments 1 to 3 by using the locus of slack logic. Additionally, a postbottleneck locus of the BCE was ruled out in Experiment 4 by using the effect propagation logic. To further support this latter conclusion, Experiment 5 applied a go-signal manipulation. Taken together, the results of all 5 experiments strongly suggest that the BCE has its locus in the capacity-limited stage, which contradicts the widely accepted notion that a capacity-unlimited stage of response activation preceding response selection proper is the locus of the BCE. (PsycINFO Database Record

CognitiveTask

PRP

10.1037/xlm0000408

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

A common capacity limitation for response and item selection in working memory.

Successful completion of any cognitive task requires selecting a particular action and the object the action is applied to. Oberauer (2009) suggested a working memory (WM) model comprising a declarative and a procedural part with analogous structures. One important assumption of this model is that both parts work independently of each other, and previous work has indeed reported evidence for the independent selection of memory lists and tasks, for example. The present study focused on the selection of single items in declarative and single responses in procedural WM. To this end, WM updating tasks were implemented as Task 2 in a Psychological Refractory Period setup in 3 experiments. The prediction based on the locus of slack logic is that item switch costs are present with a long but not with a short stimulus onset asynchrony. Contrary to this prediction, item switch costs were neither absent nor at least smaller at the short stimulus onset asynchrony. These results help to further constrain the WM model and thus to refine its computational implementation. (PsycINFO Database Record

CognitiveTask

PRP

10.1007/s00426-017-0851-0

Psychological research

Psychol Res

Hierarchical task organization in dual tasks: evidence for higher level task representations.

To examine whether hierarchical higher level task representations comprising the task sets of Task 1 (T1) and Task 2 (T2) are activated within each trial in dual-task situations, we combined the psychological refractory period (PRP) paradigm with the task-pair switching logic (Hirsch et al. 2017). In Experiment 1, in which subjects switched between task-pairs including a varying T1 and a constant T2, we found a PRP effect (i.e., worse performance with short stimulus onset asynchrony [SOA] than with long SOA) and task-pair switch costs in T1 and T2 (impaired performance in task-pair switches compared to task-pair repetitions). However, since in Experiment 1 there were no forward and backward response-response compatibility effects that indicated interference between T1 and T2, we could not exclude that the activation of T1 persisted into the next trial despite the intervening T2, and hence, that task-pair switch costs are due to repetition-priming effects of T1 across task-pairs rather than due to persisting activation of task-pair representations. In Experiment 2, we used a modified task-pair switching logic with a constant T1 and a varying T2, and replicated task-pair switch costs under conditions that not only rule out repetition-priming effects of T1 across task-pairs as the source of task-pair switch costs but also disentangle the effects of switching task-pairs from those of switching T1. These effects were associated in previous studies using the original task-pair switching logic. Thus, the findings of the present study strongly suggest that hierarchical higher level task representations are activated during dual-task processing.

CognitiveTask

PRP

10.1037/xhp0000309

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Higher-order cognitive control in dual tasks: Evidence from task-pair switching.

In the present study, we combined the psychological refractory period (PRP) paradigm with a novel task-pair switching logic which enabled us to isolate performance costs occurring at the global level of task-pairs. In Experiment 1, in which we used conceptually overlapping responses for Task 1 (T1) and Task 2 (T2), we generated 3 task-pairs by combining 1 of 3 visual tasks (T1) with an auditory task (T2). In addition to worse performance after a short SOA than a long SOA (i.e., PRP effect), we found impaired performance in n - 1 task-pair switches as compared to n - 1 task-pair repetitions (i.e., n - 1 task-pair switch costs), suggesting that task-pairs were activated during dual-task processing. In Experiment 2, we increased the interference between T1 and T2 by using physically overlapping responses and we again observed n - 1 task-pair switch costs. To investigate whether the activation of task-pairs is adjusted by inhibitory control, we looked at the n - 2 task-pair sequence and found performance to be better in n - 2 task-pair repetitions than in n - 2 task-pair switches in both experiments. This n - 2 task-pair repetition benefit was replicated in Experiment 3 in which no immediate task-pair repetitions were included. Hence, the evidence suggests enhanced activation rather than inhibition as a crucial selection mechanism at the global level of dual-task processing. (PsycINFO Database Record

CognitiveTask

PRP

10.1037/cep0000102

Canadian journal of experimental psychology = Revue canadienne de psychologie experimentale

Can J Exp Psychol

Using the locus-of-slack logic to determine whether inhibition of return in a cue-target paradigm is delaying early or late stages of processing.

Inhibition of return (IOR) is a phenomenon characterized by slower responses to targets at cued locations relative to those at uncued locations. Based on the results of previous research, it has been suggested that IOR affects a process at the input end of the processing continuum when it is generated while the reflexive oculomotor system is suppressed (cf. Satel, Hilchey, Wang, Story, & Klein, 2013). To test this theory, we employed a modified psychological refractory period paradigm designed to elicit input IOR with visual stimuli, allowing us to use the locus-of-slack logic to determine whether an early or late stage of processing was inhibited by IOR. On each trial a visual cue was presented, followed by an auditory target (T1) and visual target (T2) separated by a target-target onset asynchrony (TTOA) of varying lengths (200 ms, 400 ms, or 800 ms). Participants (31 young adults) were instructed to ignore the cue and respond to the targets as quickly and accurately as possible. Eye tracking was used to ensure that participants actively suppressed eye movements during trials. As predicted, the inhibitory effect of the cue was observed at the longest TTOA but not when TTOAs were short, supporting our hypothesis that, when generated while the reflexive oculomotor system is suppressed, IOR affects processing before response selection. (PsycINFO Database Record

CognitiveTask

PRP

10.3758/s13414-016-1244-y

Attention, perception & psychophysics

Atten Percept Psychophys

Asymmetric interference in concurrent time-to-contact estimation: Cousin or twin of the psychological refractory period effect?

In a reaction time (RT) task requiring fast responses to two stimuli presented close in time, human observers show a delayed RT to the second stimulus. This phenomenon has been attributed to a psychological refractory period (PRP). A similar asymmetric interference is found when performing multiple concurrent visual time-to-contact (TTC) estimations for moving objects, despite important differences between the tasks. In the present study, we studied the properties of the asymmetric interference found in the TTC task and compared them to the classical PRP effect. In Experiment 1, we varied the time interval between the two objects' arrival times to determine the dependence of the PRP-like effect on the asynchrony between the two TTCs. In Experiment 2, we investigated whether the physical or the perceived arrival order determined the asymmetric interference. Our results confirmed the existence of asymmetric interference in the multiple TTC estimation task, but also indicated important differences from the traditional PRP effect observed in the RT paradigm. The origins of these differences are discussed, as well as the practical implications.

CognitiveTask

PRP

10.1016/j.actpsy.2016.10.007

Acta psychologica

Acta Psychol (Amst)

Are participants' reports of their own reaction times reliable? Re-examining introspective limitations in active and passive dual-task paradigms.

There is a known introspective limitation in the Psychological Refractory Period (PRP) paradigm - people underestimate the dual-task costs on their second reaction time. The prevailing explanation for this is that conscious awareness of the second stimulus is delayed in time until the first task has been centrally processed. Here, we examined this effect in more detail, by comparing reaction time estimates after processing a PRP task, and after passively experiencing 'replays' of PRP trials. Even when participants had no dual-task processing demands, they did not accurately report the reaction time intervals using a visual analogue scale (the original reporting method of most introspective PRP experiments), but they did when placing markers that represent each event on a timeline. Thus, the timeline seems to better represent participants' introspective representation of the trial. Importantly, introspection limitations still existed when participants processed the PRP task and then recreated it on a timeline.

CognitiveTask

PRP

10.3758/s13423-016-1178-3

Psychonomic bulletin & review

Psychon Bull Rev

Is semantic activation from print capacity limited? Evidence from the psychological refractory period paradigm.

A widely accepted belief across a range of subfields in psychology is that print activates semantics "automatically" in some sense. One such sense is that activating semantics does not require capacity. This view is assessed here in the context of the Psychological Refractory Period (PRP) paradigm because it provides a way of determining whether semantic activation requires a form of capacity. Task 1 was tone classification. Task 2 was Stroop color naming. The distractors consisted of color words on some trials (e.g., BLUE), and semantic associates on others (e.g., TOMATO). Both types of distractors yielded a pattern of data inconsistent with the widespread view that semantic activation is capacity free.

CognitiveTask

PRP

10.1037/xhp0000277

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Separating limits on preparation versus online processing in multitasking paradigms: Evidence for resource models.

We conducted 2 multitasking experiments to examine the finding that first-task reaction times (RTs) are slower in the psychological refractory period (PRP) paradigm than in the prioritized processing (PP) paradigm. To see whether this difference between the 2 paradigms could be explained entirely by differences in first-task preparation, which would be consistent with the standard response selection bottleneck (RSB) model for multitasking interference, we compared the size of this difference for trials in which a second-task stimulus actually occurred against the size of the difference for trials without any second-task stimulus. The slowing of first-task RTs in the PRP paradigm relative to the PP paradigm was larger when the second-task stimulus appeared than when it did not, indicating that the difference cannot be explained entirely by between-paradigm differences in first-task preparation. Instead, the results suggest that the slowing of first-task RTs in the PRP paradigm relative to the PP paradigm is partly because of differences between paradigms in the online reallocation of processing capacity to tasks. Thus, the present results provide new evidence supporting resource models over the RSB model. (PsycINFO Database Record

CognitiveTask

PRP

10.1080/17470218.2016.1245348

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Concurrent deployment of visual attention and response selection bottleneck in a dual-task: Electrophysiological and behavioural evidence.

Visual attention and response selection are limited in capacity. Here, we investigated whether visual attention requires the same bottleneck mechanism as response selection in a dual-task of the psychological refractory period (PRP) paradigm. The dual-task consisted of an auditory two-choice discrimination Task 1 and a conjunction search Task 2, which were presented at variable temporal intervals (stimulus onset asynchrony, SOA). In conjunction search, visual attention is required to select items and to bind their features resulting in a serial search process around the items in the search display (i.e., set size). We measured the reaction time of the visual search task (RT2) and the N2pc, an event-related potential (ERP), which reflects lateralized visual attention processes. If the response selection processes in Task 1 influence the visual attention processes in Task 2, N2pc latency and amplitude would be delayed and attenuated at short SOA compared to long SOA. The results, however, showed that latency and amplitude were independent of SOA, indicating that visual attention was concurrently deployed to response selection. Moreover, the RT2 analysis revealed an underadditive interaction of SOA and set size. We concluded that visual attention does not require the same bottleneck mechanism as response selection in dual-tasks.

CognitiveTask

PRP

10.1037/xlm0000329

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Isolating component processes of posterror slowing with the psychological refractory period paradigm.

Posterror slowing (PES) refers to an increased response time following errors. While PES has traditionally been attributed to control adjustments, recent evidence suggested that PES reflects interference. The present study investigated the hypothesis that control and interference represent 2 components of PES that differ with respect to their time course and task-specificity. To this end, we investigated PES in a dual-task paradigm in which participants had to classify colors and tones that were separated by a variable stimulus onset asynchrony (SOA). Errors in the color task caused PES both in the tone task of the same trial and the color task of the subsequent trial. However, while the former effect disappeared with an increasing SOA, the latter effect was independent of SOA and lasted for several trials. This suggests that errors simultaneously induce task-unspecific, transient PES reflecting interference and task-specific, more long-lasting PES reflecting control adjustments. (PsycINFO Database Record

CognitiveTask

PRP

10.1016/j.actpsy.2016.08.008

Acta psychologica

Acta Psychol (Amst)

Attentional constraints on semantic activation: Evidence from Stroop's paradigm.

It is widely believed that semantic activation from print is automatic in the sense that it is capacity free. Two experiments addressed this issue in the context of the Psychological Refractory Period (PRP) paradigm. Participants identified whether a tone was high or low in pitch in Task 1, and named the color carried by an irrelevant word in Task 2. Tasks 1 and 2 were separated by a short or long SOA. In Experiment 1 incongruent color words and neutral words served as irrelevant distractors, whereas in Experiment 2 the distractors consisted of incongruent color associates (e.g., tomato) and the same set of neutral items. Additionally, the proportion of short and long SOAs between Task 1 and Task 2 varied across blocks, within subjects (e.g., 80:20), so as to determine whether the bottlenecking of semantic activation and response competition reported previously is best construed as structural, or subject to performance optimization. Replicating Miller, Ulrich, and Rolke (2009), SOA Proportion interacted with SOA in both experiments, consistent with performance optimization. In contrast, replicating Besner and Reynolds (2014), SOA and Congruency had additive effects on RT in both experiments, consistent with an account in which both response competition and semantic activation are bottlenecked. The best account to date is that (i) semantic processing and response competition are structurally bottlenecked (require some form of capacity), whereas (ii) other anonymous processes are subject to performance optimization.

CognitiveTask

PRP

10.3758/s13414-016-1158-8

Attention, perception & psychophysics

Atten Percept Psychophys

On the relationship between response selection and response inhibition: An individual differences approach.

The abilities to select appropriate responses and suppress unwanted actions are key executive functions that enable flexible and goal-directed behavior. However, to date it has been unclear whether these two cognitive operations tap a common action control resource or reflect two distinct processes. In the present study, we used an individual differences approach to examine the underlying relationships across seven paradigms that varied in their response selection and response inhibition requirements: stop-signal, go-no-go, Stroop, flanker, single-response selection, psychological refractory period, and attentional blink tasks. A confirmatory factor analysis suggested that response inhibition and response selection are separable, with stop-signal and go-no-go task performance being related to response inhibition, and performance in the psychological refractory period, Stroop, single-response selection, and attentional blink tasks being related to response selection. These findings provide evidence in support of the hypothesis that response selection and response inhibition reflect two distinct cognitive operations.

CognitiveTask

PRP

10.3758/s13423-016-1111-9

Psychonomic bulletin & review

Psychon Bull Rev

The role of central attention in retrieval from visual short-term memory.

The role of central attention in visual short-term memory (VSTM) encoding and maintenance is well established, yet its role in retrieval has been largely unexplored. This study examined the involvement of central attention in retrieval from VSTM using a dual-task paradigm. Participants performed a color change-detection task. Set size varied between 1 and 3 items, and the memory sample was maintained for either a short or a long delay period. A secondary tone discrimination task was introduced at the end of the delay period, shortly before the appearance of a central probe, and occupied central attention while participants were searching within VSTM representations. Similarly to numerous previous studies, reaction time increased as a function of set size reflecting the occurrence of a capacity-limited memory search. When the color targets were maintained over a short delay, memory was searched for the most part without the involvement of central attention. However, with a longer delay period, the search relied entirely on the operation of central attention. Taken together, this study demonstrates that central attention is involved in retrieval from VSTM, but the extent of its involvement depends on the duration of the delay period. Future studies will determine whether the type of memory search (parallel or serial) carried out during retrieval depends on the nature of the attentional mechanism involved the task.

CognitiveTask

PRP

10.3758/s13414-016-1161-0

Attention, perception & psychophysics

Atten Percept Psychophys

Temporal discrimination of one's own reaction times in dual-task performance: Context effects and methodological constraints.

In this study we used the method of constant stimuli to investigate introspective reaction times in the psychological refractory period (PRP) paradigm under different temporal contexts. Previous introspective PRP studies have mostly used visual analogue scales to assess introspective reaction times and found that participants were largely unaware of the typical dual-task costs that arise in this paradigm (PRP effect). This apparent limitation of introspection has been taken as evidence for a serial processing bottleneck that encompasses response selection as well as conscious perception. In our study, in each trial participants first performed the PRP task and were then presented with a comparison interval that they had to compare with their reaction time to the second task (RT2). Across three experiments, we observed that the subjective estimates of RT2 (i.e., the points of subjective equality) did not reflect the objective pattern but were almost completely biased toward the center of the comparison intervals (asymmetry effect). In a control experiment in which participants discriminated RT2s of other participants without performing the PRP task, this bias was largely reduced. We interpret these results as indicating that in dual-task performance participants acquire only poor temporal representations of their own reaction times, and the apparent unawareness of the PRP effect may reflect disturbed timing abilities rather than a conscious perception bottleneck.

CognitiveTask

PRP

10.1016/j.actpsy.2016.04.010

Acta psychologica

Acta Psychol (Amst)

Serial or overlapping processing in multitasking as individual preference: Effects of stimulus preview on task switching and concurrent dual-task performance.

Understanding the mechanisms and performance consequences of multitasking has long been in focus of scientific interest, but has been investigated by three research lines more or less isolated from each other. Studies in the fields of the psychological refractory period, task switching, and interruptions have scored with a high experimental control, but usually do not give participants many degrees of freedom to self-organize the processing of two concurrent tasks. Individual strategies as well as their impact on efficiency have mainly been neglected. Self-organized multitasking has been investigated in the field of human factors, but primarily with respect to overall performance without detailed investigation of how the tasks are processed. The current work attempts to link aspects of these research lines. All of them, explicitly or implicitly, provide hints about an individually preferred type of task organization, either more cautious trying to work strictly serially on only one task at a time or more daring with a focus on task interleaving and, if possible, also partially overlapping (parallel) processing. In two experiments we investigated different strategies of task organization and their impact on efficiency using a new measure of overall multitasking efficiency. Experiment 1 was based on a classical task switching paradigm with two classification tasks, but provided one group of participants with a stimulus preview of the task to switch to next, enabling at least partial overlapping processing. Indeed, this preview led to a reduction of switch costs and to an increase of dual-task efficiency, but only for a subgroup of participants. They obviously exploited the possibility of overlapping processing, while the others worked mainly serially. While task-sequence was externally guided in the first experiment, Experiment 2 extended the approach by giving the participants full freedom of task organization in concurrent performance of the same tasks. Fine-grained analyses of response scheduling again revealed individual differences regarding the preference for strictly serial processing vs. some sort of task interleaving and overlapping processing. However, neither group showed a striking benefit in dual-task efficiency, although the results show that the costs of multitasking can partly be compensated by overlapping processing.

CognitiveTask

PRP

10.3758/s13414-016-1113-8

Attention, perception & psychophysics

Atten Percept Psychophys

Backward compatibility effects in younger and older adults.

In many dual-task situations, responses to the second of two tasks are slowed when the time between tasks is short. The response-selection bottleneck model of dual-task performance accounts for this phenomenon by assuming that central processing of the second task is blocked by a bottleneck until central processing of Task 1 is complete. This assumption could be called into question if it could be demonstrated that the response to Task 2 affected the central processing of Task 1, a backward response compatibility effect. Such effects are well-established in younger adults. Backward compatibility effects in older (as well as younger) adults were explored in two experiments. The first experiment found clear backward response compatibility effects for younger adults but no evidence of them for older adults. The second experiment explored backward stimulus compatibility and found similar effects in both younger and older adults. Evidence possibly consistent with some pre-bottleneck processing of Task 2 central stages also was found in the second experiment in both age groups. For younger adults, the results provide further evidence falsifying the claim of an immutable response selection bottleneck. For older adults, the evidence suggested that Task 2 affects Task 1 when there is stimulus compatibility but not when there is response compatibility.

CognitiveTask

PRP

10.1007/s00221-016-4649-x

Experimental brain research

Exp Brain Res

The role of the dorsal medial frontal cortex in central processing limitation: a transcranial magnetic stimulation study.

When humans perform two tasks simultaneously, responses to the second task are increasingly delayed as the interval between the two tasks decreases (psychological refractory period). This delay of the second task is thought to reflect a central processing limitation at the response selection stage. However, the neural mechanisms underlying this central processing limitation remain unclear. Using transcranial magnetic stimulation (TMS), we examined the role of the dorsal medial frontal cortex (dMFC) in a dual-task paradigm in which participants performed an auditory task 1 and a visual task 2. We found that dMFC TMS, relative to control conditions, reduced the psychological refractory period for task 2 processing, whereas we observed no dMFC TMS effects on task 1 processing. This suggests a causal role of the dMFC in coordinating response selection processes at the central bottleneck.

CognitiveTask

PRP

10.3758/s13423-016-1020-y

Psychonomic bulletin & review

Psychon Bull Rev

Do Arabic numerals activate magnitude automatically? Evidence from the psychological refractory period paradigm.

A single experiment (N = 30) tested the claim that Arabic numerals automatically activate their magnitude representations by assessing whether central attention is required in order to activate magnitude within the psychological refractory period (PRP) paradigm. Subjects performed a color discrimination task as Task 1 and a parity judgment task as Task 2. Task overlap was controlled by varying stimulus onset asynchrony (SOA). A spatial-numerical association of response codes (SNARC) effect arose in Task 2 and yielded under-additive effects with decreasing SOA. This result suggests that magnitude is activated prior to central attention, and is therefore consistent with the claim that numerals activate magnitude automatically.

CognitiveTask

PRP

10.3389/fnhum.2016.00119

Frontiers in human neuroscience

Front Hum Neurosci

Central as well as Peripheral Attentional Bottlenecks in Dual-Task Performance Activate Lateral Prefrontal Cortices.

Human information processing suffers from severe limitations in parallel processing. In particular, when required to respond to two stimuli in rapid succession, processing bottlenecks may appear at central and peripheral stages of task processing. Importantly, it has been suggested that executive functions are needed to resolve the interference arising at such bottlenecks. The aims of the present study were to test whether central attentional limitations (i.e., bottleneck at the decisional response selection stage) as well as peripheral limitations (i.e., bottleneck at response initiation) both demand executive functions located in the lateral prefrontal cortex. For this, we re-analyzed two previous studies, in which a total of 33 participants performed a dual-task according to the paradigm of the psychological refractory period (PRP) during functional magnetic resonance imaging (fMRI). In one study (N = 17), the PRP task consisted of two two-choice response tasks known to suffer from a central bottleneck (CB group). In the other study (N = 16), the PRP task consisted of two simple-response tasks known to suffer from a peripheral bottleneck (PB group). Both groups showed considerable dual-task costs in form of slowing of the second response in the dual-task (PRP effect). Imaging results are based on the subtraction of both single-tasks from the dual-task within each group. In the CB group, the bilateral middle frontal gyri and inferior frontal gyri were activated. Higher activation in these areas was associated with lower dual-task costs. In the PB group, the right middle frontal and inferior frontal gyrus (IFG) were activated. Here, higher activation was associated with higher dual-task costs. In conclusion we suggest that central and peripheral bottlenecks both demand executive functions located in lateral prefrontal cortices (LPFC). Differences between the CB and PB groups with respect to the exact prefrontal areas activated and the correlational patterns suggest that the executive functions resolving interference at least partially differ between the groups.

CognitiveTask

PRP

10.1016/j.cognition.2016.02.003

Cognition

Cognition

Eliminating dual-task costs by minimizing crosstalk between tasks: The role of modality and feature pairings.

We tested the independent influences of two content-based factors on dual-task costs, and on the parallel processing ability: The pairing of S-R modalities and the pairing of relevant features between stimuli and responses of two tasks. The two pairing factors were realized across four dual-task groups. Within each group the two tasks comprised two different stimulus modalities (visual and auditory), two different relevant stimulus features (spatial and verbal) and two response modalities (manual and vocal). Pairings of S-R modalities (standard: visual-manual and auditory-vocal, non-standard: visual-vocal and auditory-manual) and feature pairings (standard: spatial-manual and verbal-vocal, non-standard: spatial-vocal and verbal-manual) varied across groups. All participants practiced their respective dual-task combination in a paradigm with simultaneous stimulus onset before being transferred to a psychological refractory period paradigm varying stimulus-onset asynchrony. A comparison at the end of practice revealed similar dual-task costs and similar pairing effects in both paradigms. Dual-task costs depended on modality and feature pairings. Groups training with non-standard feature pairings (i.e., verbal stimulus features mapped to spatially separated response keys, or spatial stimulus features mapped to verbal responses) and non-standard modality pairings (i.e., auditory stimulus mapped to manual response, or visual stimulus mapped to vocal responses) had higher dual-task costs than respective standard pairings. In contrast, irrespective of modality pairing dual-task costs virtually disappeared with standard feature pairings after practice in both paradigms. The results can be explained by crosstalk between feature-binding processes for the two tasks. Crosstalk was present for non-standard but absent for standard feature pairings. Therefore, standard feature pairings enabled parallel processing at the end of practice.

CognitiveTask

PRP

10.1016/j.neuron.2015.10.040

Neuron

Neuron

Time-Resolved Decoding of Two Processing Chains during Dual-Task Interference.

The human brain exhibits fundamental limitations in multitasking. When subjects engage in a primary task, their ability to respond to a second stimulus is degraded. Two competing models of multitasking have been proposed: either cognitive resources are shared between tasks, or they are allocated to each task serially. Using a novel combination of magneto-encephalography and multivariate pattern analyses, we obtained a precise spatio-temporal decomposition of the brain processes at work during multitasking. We discovered that each task relies on a sequence of brain processes. These sequences can operate in parallel for several hundred milliseconds but beyond ∼ 500 ms, they repel each other: processes evoked by the first task are shortened, while processes of the second task are either lengthened or postponed. These results contradict the resource-sharing model and further demonstrate that the serial model is incomplete. We therefore propose a new theoretical framework for the computational architecture underlying multitasking.

CognitiveTask

PRP

10.3758/s13414-015-0998-y

Attention, perception & psychophysics

Atten Percept Psychophys

Dual-task backward compatibility effects are episodically mediated.

In dual-task performance, the backward compatibility effect (BCE; faster Task 1 reaction time when Task 1 and Task 2 responses are compatible) is thought to represent automatic activation of Task 2 response information in parallel with attended Task 1 performance. Work by Hommel and Eglau (Psychological Research, 66, 260-273, 2002) has suggested the BCE relies on stimulus-response learning in long-term memory. Subsequent work by Ellenbogen and Meiran (Memory and Cognition, 36, 968-978, 2008), however, proposed that the BCE is mediated by Task 2 rules held in working memory (WM) during Task 1 performance. The present study aimed to dissociate these two theoretical claims. In Experiment 1, we assessed the effects of prior single-task practice with Task 1 or Task 2 of a subsequent dual-task paradigm. Where the WM-mediated model predicts both BCE and overall reaction time improvement relative to prior task practice, an episodic learning model makes divergent predictions for BCE based on the context specificity of prior Task 2 learning. Results showed a close fit with episodic predictions and contradicted WM model predictions. Experiment 2 examined the finer grained timecourse of BCE over initial development, subsequent interference of this initial learning on BCE development with new conflicting Task 2 response mappings, and finally reestablishment of BCE in the original dual task. Data again showed close agreement with long-term learning predictions. We argue in favor of an episodic account of the BCE, and consider implications of WM and episodic mechanisms of automatic response activation on other aspects of dual-task performance.

CognitiveTask

PRP

10.3389/fpsyg.2015.01590

Frontiers in psychology

Front Psychol

Better dual-task processing in simultaneous interpreters.

Simultaneous interpreting (SI) is a highly complex activity and requires the performance and coordination of multiple, simultaneous tasks: analysis and understanding of the discourse in a first language, reformulating linguistic material, storing of intermediate processing steps, and language production in a second language among others. It is, however, an open issue whether persons with experience in SI possess superior skills in coordination of multiple tasks and whether they are able to transfer these skills to lab-based dual-task situations. Within the present study, we set out to explore whether interpreting experience is associated with related higher-order executive functioning in the context of dual-task situations of the Psychological Refractory Period (PRP) type. In this PRP situation, we found faster reactions times in participants with experience in simultaneous interpretation in contrast to control participants without such experience. Thus, simultaneous interpreters possess superior skills in coordination of multiple tasks in lab-based dual-task situations.

CognitiveTask

PRP

10.1007/s00426-015-0711-8

Psychological research

Psychol Res

Age-related emotional bias in processing two emotionally valenced tasks.

Previous studies suggest that older adults process positive emotions more efficiently than negative emotions, whereas younger adults show the reverse effect. We examined whether this age-related difference in emotional bias still occurs when attention is engaged in two emotional tasks. We used a psychological refractory period paradigm and varied the emotional valence of Task 1 and Task 2. In both experiments, Task 1 was emotional face discrimination (happy vs. angry faces) and Task 2 was sound discrimination (laugh, punch, vs. cork pop in Experiment 1 and laugh vs. scream in Experiment 2). The backward emotional correspondence effect for positively and negatively valenced Task 2 on Task 1 was measured. In both experiments, younger adults showed a backward correspondence effect from a negatively valenced Task 2, suggesting parallel processing of negatively valenced stimuli. Older adults showed similar negativity bias in Experiment 2 with a more salient negative sound ("scream" relative to "punch"). These results are consistent with an arousal-bias competition model [Mather and Sutherland (Perspectives in Psychological Sciences 6:114-133, 2011)], suggesting that emotional arousal modulates top-down attentional control settings (emotional regulation) with age.

CognitiveTask

PRP

10.3389/fpsyg.2015.01366

Frontiers in psychology

Front Psychol

Efficient multitasking: parallel versus serial processing of multiple tasks.

In the context of performance optimizations in multitasking, a central debate has unfolded in multitasking research around whether cognitive processes related to different tasks proceed only sequentially (one at a time), or can operate in parallel (simultaneously). This review features a discussion of theoretical considerations and empirical evidence regarding parallel versus serial task processing in multitasking. In addition, we highlight how methodological differences and theoretical conceptions determine the extent to which parallel processing in multitasking can be detected, to guide their employment in future research. Parallel and serial processing of multiple tasks are not mutually exclusive. Therefore, questions focusing exclusively on either task-processing mode are too simplified. We review empirical evidence and demonstrate that shifting between more parallel and more serial task processing critically depends on the conditions under which multiple tasks are performed. We conclude that efficient multitasking is reflected by the ability of individuals to adjust multitasking performance to environmental demands by flexibly shifting between different processing strategies of multiple task-component scheduling.

CognitiveTask

PRP

10.1037/xhp0000103

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

A comparison of the psychological refractory period and prioritized processing paradigms: Can the response-selection bottleneck model explain them both?

Four experiments examined whether well-established phenomena from the psychological refractory period (PRP) paradigm are also observed in the prioritized processing paradigm, as would be expected from a common description of the 2 paradigms with the response selection bottleneck (RSB) model. Consistent with a generalization of the RSB model to the prioritized processing paradigm, Experiments 1 and 2 showed that this paradigm yields effects of SOA and stimulus discriminability analogous to those observed in the PRP paradigm. In Experiments 3 and 4, however, overall RTs and effect sizes differed between the PRP and prioritized processing paradigms in ways that are difficult to explain within the RSB model. Understanding the differences between these 2 paradigms offers considerable promise as a way to extend the RSB model beyond the domain of the PRP paradigm and to generalize our understanding of multitasking interference.

CognitiveTask

PRP

10.1016/j.bandc.2015.05.001

Brain and cognition

Brain Cogn

Shedding light on the effect of priority instructions during dual-task performance in younger and older adults: A fNIRS study.

Age-related differences in the ability to perform two tasks simultaneously (or dual-task) have become a major concern in aging neurosciences and have often been assessed with two distinct paradigms; the Psychological Refractory Period (PRP) and the Dual-Task (DT) paradigms. PRP studies assess participants when they give Priority to one task over the other (complete A then B), whereas in DT studies participants give Equal priority to both tasks (complete A and B). The Equal condition could be viewed as adding an executive control component to the task since the participants must spontaneously monitor attention between tasks. In the current study, we assessed the effect of priority instructions (Priority vs. Equal) on the dual-task performance and brain activity of younger (n = 16) and older adults (n = 19) with functional near infra-red spectroscopy (fNIRS). In younger adults, the Priority condition showed right-sided activation in the prefrontal cortex during DT execution. Older adults showed bilateral frontal activation, yet restrained to specific areas. They showed increased activation in DT vs. single task condition in the left dorsolateral prefrontal cortex (DLPFC) and the bilateral ventrolateral prefrontal cortex (VLPFC). In the Equal condition, the DT condition showed isolated left DLPFC and VLPFC activation in younger adults and widespread bilateral DLPFC activation in older adults. These results suggest that for both older and younger adults, priority effects are associated with distinct patterns of prefrontal activation. Age-related differences also exist in these patterns such that prefrontal activation seems to be more spread out at different sites in older adults when they are instructed to give Equal priority to both tasks.

CognitiveTask

PRP

10.1016/j.actpsy.2015.04.003

Acta psychologica

Acta Psychol (Amst)

A startling acoustic stimulus interferes with upcoming motor preparation: Evidence for a startle refractory period.

When a startling acoustic stimulus (SAS) is presented in a simple reaction time (RT) task, response latency is significantly shortened. The present study used a SAS in a psychological refractory period (PRP) paradigm to determine if a shortened RT1 latency would be propagated to RT2. Participants performed a simple RT task with an auditory stimulus (S1) requiring a vocal response (R1), followed by a visual stimulus (S2) requiring a key-lift response (R2). The two stimuli were separated by a variable stimulus onset asynchrony (SOA), and a typical PRP effect was found. When S1 was replaced with a 124dB SAS, R1 onset was decreased by 40-50ms; however, rather than the predicted propagation of a shortened RT, significantly longer responses were found for RT2 on startle trials at short SOAs. Furthermore, the 100ms SOA condition exhibited reduced peak EMG for R2 on startle trials, as compared to non-startle trials. These results are attributed to the startling stimulus temporarily interfering with cognitive processing, delaying and altering the execution of the second response. In addition to this "startle refractory period," results also indicated that RT1 latencies were significantly lengthened for trials that immediately followed a startle trial, providing evidence for longer-term effects of the startling stimulus.

CognitiveTask

PRP

10.3389/fpsyg.2015.00403

Frontiers in psychology

Front Psychol

On the importance of Task 1 and error performance measures in PRP dual-task studies.

The psychological refractory period (PRP) paradigm is a dominant research tool in the literature on dual-task performance. In this paradigm a first and second component task (i.e., Task 1 and Task 2) are presented with variable stimulus onset asynchronies (SOAs) and priority to perform Task 1. The main indicator of dual-task impairment in PRP situations is an increasing Task 2-RT with decreasing SOAs. This impairment is typically explained with some task components being processed strictly sequentially in the context of the prominent central bottleneck theory. This assumption could implicitly suggest that processes of Task 1 are unaffected by Task 2 and bottleneck processing, i.e., decreasing SOAs do not increase reaction times (RTs) and error rates of the first task. The aim of the present review is to assess whether PRP dual-task studies included both RT and error data presentations and statistical analyses and whether studies including both data types (i.e., RTs and error rates) show data consistent with this assumption (i.e., decreasing SOAs and unaffected RTs and/or error rates in Task 1). This review demonstrates that, in contrast to RT presentations and analyses, error data is underrepresented in a substantial number of studies. Furthermore, a substantial number of studies with RT and error data showed a statistically significant impairment of Task 1 performance with decreasing SOA. Thus, these studies produced data that is not primarily consistent with the strong assumption that processes of Task 1 are unaffected by Task 2 and bottleneck processing in the context of PRP dual-task situations; this calls for a more careful report and analysis of Task 1 performance in PRP studies and for a more careful consideration of theories proposing additions to the bottleneck assumption, which are sufficiently general to explain Task 1 and Task 2 effects.

CognitiveTask

PRP

10.3758/s13414-015-0874-9

Attention, perception & psychophysics

Atten Percept Psychophys

Are processing limitations of visual attention and response selection subject to the same bottleneck in dual-tasks?

Visual attention and response selection are processes that are limited by capacity. The present study focuses on whether visual attention is subject to the response selection bottleneck. This was investigated by conducting 2 dual-task experiments of the psychological refractory period (PRP) type. A visual conjunction search task was chosen as Task 2 in these experiments. Conjunction search requires the binding of the stimulus' defining features. This binding is performed in a serial search process in displays of different amounts of stimuli until the presence or absence of the target is correctly indicated. In Experiment 1, the conjunction search was combined with a 2-choice tone discrimination Task 1, and in Experiment 2 with a 2-choice color discrimination Task 1. Detailed reaction time (RT) analyses revealed concurrent performance of visual search to both tone and color in Task 1's response selection. In conclusion, visual attention is not subject to the response selection bottleneck.

CognitiveTask

PRP

10.1037/pag0000015

Psychology and aging

Psychol Aging

Ideomotor-compatible tasks partially escape dual-task interference in both young and elderly adults.

Under most circumstances, it is not possible to carry out central processing for 2 tasks at the same time; effectively there is a bottleneck. Nevertheless, in 2 experiments it is demonstrated here that both younger and older adults are able to partially bypass the bottleneck in a psychological refractory period procedure, even without extensive training, when the 2nd of the 2 tasks is a saccade or a body tilt in the direction of rotation of a visual stimulus. Consistent with earlier research, the findings showed that younger adults can bypass when the second task has ideomotor-compatible stimuli and responses. Most strikingly, they demonstrated that bypass can also occur in older adults. Overall, the findings are inconsistent with any categorical claim that younger adults can bypass the dual-task bottleneck whereas older adults cannot. The construct of ideomotor-compatible tasks may comprise 2 quite different classes of experimental procedures.

CognitiveTask

PRP

10.3758/s13414-014-0804-2

Attention, perception & psychophysics

Atten Percept Psychophys

Are introspective reaction times affected by the method of time estimation? A comparison of visual analogue scales and reproduction.

In this study, we investigated whether the method of time estimation plays a role in the apparent limits of introspection in dual-task processing. Previous studies showed that when participants reported introspective reaction times after each trial of a dual task by clicking on a visual analogue scale, they appeared to be unaware of the dual-task costs in their performance. However, visual analogue scales have seldom been used in interval estimation, and they may be inappropriate. In the present study, after each dual-task trial, participants reported their introspective reaction times either via a visual analogue scale or via the method of reproduction. The results replicated the previous findings, irrespective of method. That is, even though responses to the second task slowed down with increasing task overlap, this slowing was only very weakly reflected in the introspective reaction times. Thus, the participants' failure to report the objective dual-task costs in their reaction times is a rather robust finding that cannot be attributed to the method employed. However, introspective reaction times reported via visual analogue scales were more closely related to the objective reaction times, suggesting that visual analogue scales are preferable to reproduction. We conclude that introspective reaction times represent the same information regardless of method, but whether that information is temporal in nature is as yet unsettled.

CognitiveTask

PRP

10.1016/j.cognition.2014.10.004

Cognition

Cognition

Contribution of motor representations to action verb processing.

Electrophysiological and brain imaging studies show a somatotopic activation of the premotor cortex while subjects process action verbs. This somatotopic motor activation has been taken as an indication that the meaning of action verbs is embedded in motor representations. However, discrepancies in the literature led to the alternative hypothesis that motor representations are activated during the course of a mental imagery process emerging only after the meaning of the action has been accessed. In order to address this issue, we asked participants to decide whether a visually presented verb was concrete or abstract by pressing a button or a pedal (primary task) and then to provide a distinct vocal response to low and high sounds played soon after the verb display (secondary task). Manipulations of the visual display (lower vs. uppercase), verb imageability (concrete vs. abstract), verb meaning (hand vs. foot-related), and response effector (hand vs. foot) allowed us to trace the perceptual, semantic and response stages of verb processing. We capitalized on the psychological refractory period (PRP), which implies that the initiation of the secondary task should be delayed only by those factors that slow down the central decision process in the primary task. In line with this prediction, our results showed that the time cost resulting from the processing of abstract verbs, when compared to concrete verbs, was still observed in the subsequent response to the sounds, whereas the overall advantage of hand over foot responses did not influence sound judgments. Crucially, we also observed a verb-effector compatibility effect (i.e., foot-related verbs are responded faster with the foot and hand-related verbs with the hand) that contaminated the performance of the secondary task, providing clear evidence that motor interference from verb meaning occurred during the central decision stage. These results cannot be explained by a mental imagery process that would deploy only during the execution of the response to verb judgments. They rather indicate that the motor activation induced by action verbs accompanies the lexico-semantic processes leading to response selection.

CognitiveTask

PRP

10.3758/s13423-014-0773-4

Psychonomic bulletin & review

Psychon Bull Rev

A cognitive framework for explaining serial processing and sequence execution strategies.

Behavioral research has produced many task-specific cognitive models that do not say much about the underlying information-processing architecture. Such an architecture is badly needed to better understand how cognitive neuroscience can benefit from existing cognitive models. This problem is especially pertinent in the domain of sequential behavior where behavioral research suggests a diversity of cognitive processes, processing modes and representations. Inspired by decades of reaction time (RT) research with the Additive Factors Method, the Psychological Refractory Period paradigm, and the Discrete Sequence Production task, we propose the Cognitive framework for Sequential Motor Behavior (C-SMB). We argue that C-SMB accounts for cognitive models developed for a range of sequential motor tasks (like those proposed by Keele et al., Psychological Review, 110(2), 316-339, 2003; Rosenbaum et al., Journal of Experimental Psychology: Human Perception and Performance, 9(1), 86-102, 1983, Journal of Memory and Language, 25, 710-725, 1986, Psychological Review, 102, 28-67, 1995; Schmidt, Psychological Review, 82(4), 225-260, 1975; Sternberg et al., 1978, Phonetica, 45, 177-197, 1988). C-SMB postulates that sequence execution can be controlled by a central processor using central-symbolic representations, and also by a motor processor using sequence-specific motor representations. On the basis of this framework, we present a classification of the sequence execution strategies that helps researchers to better understand the cognitive and neural underpinnings of serial movement behavior.

CognitiveTask

PRP

10.1016/j.concog.2014.07.016

Consciousness and cognition

Conscious Cogn

Distorted subjective reports of stimulus onsets under dual-task conditions: Delayed conscious perception or estimation bias?

We investigated whether selecting a response for one task delays the conscious perception of another stimulus (delayed conscious perception hypothesis). In two experiments, participants watched a revolving clock hand while performing two tasks in close succession (i.e. a dual-task). Two stimuli were presented with varying stimulus onset asynchrony (SOA). After each trial, participants separately estimated the onsets of the two stimuli on the clock face. Across two experiments and four conditions, we manipulated response requirements and assessed their impact on perceived stimulus onsets. Results showed that (a) providing speeded responses to the stimuli did lead to greater SOA-dependent misperceptions of both stimulus onsets as compared to a solely perceptual condition, and (b) that response grouping reduced these misperceptions. Overall, the results provide equivocal evidence for the delayed conscious perception hypothesis. They rather suggest that participants' estimates of the two stimulus onsets are biased by the interval between their responses.

CognitiveTask

PRP

10.3389/fnagi.2014.00193

Frontiers in aging neuroscience

Front Aging Neurosci

The neural architecture of age-related dual-task interferences.

In daily life elderly adults exhibit deficits when dual-tasking is involved. So far these deficits have been verified on a behavioral level in dual-tasking. Yet, the neuronal architecture of these deficits in aging still remains to be explored especially when late-middle aged individuals around 60 years of age are concerned. Neuroimaging studies in young participants concerning dual-tasking were, among others, related to activity in middle frontal (MFG) and superior frontal gyrus (SFG) and the anterior insula (AI). According to the frontal lobe hypothesis of aging, alterations in these frontal regions (i.e., SFG and MFG) might be responsible for cognitive deficits. We measured brain activity using fMRI, while examining age-dependent variations in dual-tasking by utilizing the PRP (psychological refractory period) test. Behavioral data showed an increasing PRP effect in late-middle aged adults. The results suggest the age-related deteriorated performance in dual-tasking, especially in conditions of risen complexity. These effects are related to changes in networks involving the AI, the SFG and the MFG. The results suggest that different cognitive subprocesses are affected that mediate the observed dual-tasking problems in late-middle aged individuals.

CognitiveTask

PRP

10.3758/s13414-014-0730-3

Attention, perception & psychophysics

Atten Percept Psychophys

"Just do it when you get a chance": the effects of a background task on primary task performance.

Two experiments investigated multitasking performance with a new "prioritized-processing paradigm" in which participants responded only to a high-priority primary task when this task required some action, responding to a low-priority background task only when no action was required for the primary task. In both experiments, performance was worse on the primary task than on the same task performed in isolation, indicating that this attempt to give absolute priority to the primary task is not sufficient to protect it from multitasking interference. Multitasking interference was present for task-repetition trials as well as task-alternation trials, so the interference could not be completely explained as a task-switching cost. In addition, responses to the primary task were influenced by their compatibility with the responses associated with the stimulus for the background task, indicating that there was some activation of S-R associations within the background task even when this task did not require any response. The findings generalize a number of effects from the psychological refractory period and task-switching paradigms to the prioritized-processing paradigm, thereby providing hints as to the underlying mechanisms responsible for those effects. The "prioritized-processing paradigm" appears to have several desirable features for the study of multitasking interference.

CognitiveTask

PRP

10.1007/s00429-014-0847-0

Brain structure & function

Brain Struct Funct

Parallel and serial processing in dual-tasking differentially involves mechanisms in the striatum and the lateral prefrontal cortex.

The lateral prefrontal cortex and the basal ganglia are known to be important for response selection processes, also in dual-task situations. However, response selection in dual-task situations can be achieved using different modes ranging from a parallel selection to a more serial selection of responses. Nothing is known whether differences in these processing modes during dual-tasking have distinct functional neuroanatomical correlates. In this fMRI study we analyzed performance in a psychological refractory period paradigm. In this paradigm we design a PRP task where we vary the frequency of short and long stimulus onset asynchronies between the two tasks. Using mathematical constraints we interpret the effects of this manipulation with respect to processing modes ranging from more serial to more parallel response selection. Contrastingly these blocks showed that response selection in dual-tasking under the constraint of more parallel processing is mediated by mechanisms operating at the striatal level, while response selection under the constraint of more serial processing is mediated via mechanisms operating in the lateral prefrontal cortex. The results suggest that lateral prefrontal and striatal regions are 'optimized' for a certain processing modes in dual tasking.

CognitiveTask

PRP

10.1016/j.concog.2014.05.011

Consciousness and cognition

Conscious Cogn

Introspective reports of reaction times in dual-tasks reflect experienced difficulty rather than timing of cognitive processes.

Reports of introspective reaction times (iRTs) have been used to investigate conscious awareness during dual-task situations. Previous studies showed that dual-task costs in RTs (the psychological refractory period, PRP, effect) are not reflected in participants' introspective reports. This finding has been attributed to conscious awareness of Task 2 being delayed while Task 1 is centrally processed. Here, we test this Temporal model and compare it to an alternative that assumes participants base their iRTs on experienced difficulty. We collected iRTs and difficulty estimates after each trial of a PRP paradigm in which the perceptual difficulty of either Task 2 (Experiment 1) or Task 1 (Experiment 2) was manipulated. Our results largely support the difficulty-based account, suggesting that in a dual-task situation, iRTs do not reflect timing of cognitive processes but are strongly influenced by the experience of difficulty.

CognitiveTask

PRP

10.1016/j.actpsy.2014.05.011

Acta psychologica

Acta Psychol (Amst)

The locus of the emotional Stroop effect: a study with the PRP paradigm.

Stimuli that are clearly positive or negative (hence valence-laden stimuli) have the potential to interrupt unrelated task processing. A typical example is the emotional Stroop effect (ESE) in which responding to a certain task feature (e.g., color) is delayed by the presentation of task-irrelevant valent stimuli (e.g., negative pictures) compared to valence-neutral stimuli. Here we scrutinize which processes are slowed down by irrelevant but valent stimulation. In Experiment 1, participants performed in a Psychological Refractory Period (PRP) experiment with tone discrimination as Task 1 and color discrimination as Task 2. Importantly, colors in Task 2 were accompanied by valent or neutral pictures. Valent pictures delayed responding in Task 2 (thus an ESE) and this delay was additive to the time interval between tasks. In Experiment 2, task order was reversed and the ESE in Task 1 fully propagated to the Task 2 tone discrimination. These results imply that irrelevant valence-laden stimulation delays capacity-limited processes, and we suggest that this is a late perceptual process acting on stimulus categorization.

CognitiveTask

PRP

10.3758/s13423-014-0660-z

Psychonomic bulletin & review

Psychon Bull Rev

PRP training shows Task1 response selection is the locus of the backward response compatibility effect.

The present study investigates the effect of practice in a psychological refractory period (PRP) paradigm on the backward compatibility effect (BCE), in order to determine the locus of this response priming effect on Task1 performance. In two experiments, we show that the size of the BCE is closely associated with the duration of the response selection stage in Task1. When this stage is shortened through PRP practice, the magnitude of the BCE decreases. Subsequently increasing the duration of Task1 response selection results in a larger BCE, but manipulating the same stage in Task2 does not. Our results suggest that the BCE reflects crosstalk of unattended response information for Task2 acting on the response selection stage in Task1, and that response information for two tasks may be activated simultaneously.

CognitiveTask

PRP

10.1080/0361073X.2014.896663

Experimental aging research

Exp Aging Res

Multitasking and aging: do older adults benefit from performing a highly practiced task?

BACKGROUND/STUDY CONTEXT: The present study examined the effect of training on age differences in performing a highly practiced task using the psychological refractory period (PRP) paradigm (Pashler, 1984, Journal of Experimental Psychology: Human Perception and Performance, 10, 358-377). Earlier training studies have concentrated on tasks that are not already overlearned. The present question of interest is whether task dual-task integration will be more efficient when single-task performance is approaching asymptotic levels. Task 1 was red/green signal discrimination (green = "go" and red = "wait"; analogous to pedestrian signals) and Task 2 was tone discrimination (white noise vs. a horn "honk"; analogous to traffic sound). The stimulus onset asynchrony (SOA) between Task 1 and Task 2 was varied (50, 150, 600, and 1000 ms). All individuals participated in eight sessions spread over 8 weeks (one session per week). Participants completed a dual-task pretest (Week 1), followed by 6 weeks of single-task testing (Weeks 2-7), followed by a dual-task posttest (Week 8). Although older adults showed larger overall dual-task costs (i.e., PRP effects), they were able to reduce the costs with practice as much as younger adults. However, even when training on Task 1 results in asymptotic performance, this still did not lead to an appreciable reduction in dual-task costs. Also, older adults, but not younger adults, responded more rapidly to green stimuli than to red stimuli in the Task 1 training latency data. The authors confirmed this green/go bias using diffusion modeling, which takes into account response time and error rates at the same time. This green/go bias is potentially dangerous at crosswalks, especially when combined with large dual-task interference, and might contribute to the high rate of crosswalk accidents in the elderly.

CognitiveTask

PRP

10.1016/j.cognition.2014.03.001

Cognition

Cognition

Who is talking in backward crosstalk? Disentangling response- from goal-conflict in dual-task performance.

Responses in the second of two subsequently performed tasks can speed up compatible responses in the temporally preceding first task. Such backward crosstalk effects (BCEs) represent a challenge to the assumption of serial processing in stage models of human information processing, because they indicate that certain features of the second response have to be represented before the first response is emitted. Which of these features are actually relevant for BCEs is an open question, even though identifying these features is important for understanding the nature of parallel and serial response selection processes in dual-task performance. Motivated by effect-based models of action control, we show in three experiments that the BCE to a considerable degree reflects features of intended action effects, although features of the response proper (or response-associated kinesthetic feedback) also seem to play a role. These findings suggest that the codes of action effects (or action goals) can become activated simultaneously rather than serially, thereby creating BCEs.

CognitiveTask

PRP

10.3758/s13414-014-0638-y

Attention, perception & psychophysics

Atten Percept Psychophys

The influence of training on the attentional blink and psychological refractory period.

A growing body of research suggests that dual-task interference in sensory consolidation (e.g., the attentional blink, AB) and response selection (e.g., the psychological refractory period, PRP) stems from a common central bottleneck of information processing. With regard to response selection, it is well known that training reduces dual-task interference. We tested whether training that is known to be effective for response selection can also reduce dual-task interference in sensory consolidation. Over two experiments, performance on a PRP paradigm (Exp. 1) and on AB paradigms (differing in their stimuli and task demands, Exps. 1 and 2) was examined after participants had completed a relevant training regimen (T1 practice for both paradigms), an irrelevant training regimen (comparable sensorimotor training, not related to T1 for both tasks), a visual-search training regimen (Exp. 2 only), or after participants had been allocated to a no-training control group. Training that had shown to be effective for reducing dual-task interference in response selection was also found to be effective for reducing interference in sensory consolidation. In addition, we found some evidence that training benefits transferred to the sensory consolidation of untrained stimuli. Collectively, these findings show that training benefits can transfer across cognitive operations that draw on the central bottleneck in information processing. These findings have implications for theories of the AB and for the design of cognitive-training regimens that aim to produce transferable training benefits.

CognitiveTask

PRP

10.1068/p7534

Perception

Perception

Face perception is whole or none: disentangling the role of spatial contiguity and interfeature distances in the composite face illusion.

Compelling evidence that faces are perceived holistically or configurally comes from the composite face illusion: identical top halves of a face are perceived as being different if they are aligned with different bottom halves. The visual illusion disappears when the top and bottom face halves are spatially misaligned. Whether this is because the two halves no longer form a whole face (ie they form two segmented parts), or because of an increase in interfeatures distance in the misaligned condition (eg eyes-mouth distance) remains unclear. Here, thirty-four participants performed a delayed matching composite task in which the amount of spatial misalignment between face halves varied parametrically (from 8.33% of face width to 100%). The difference in performance between aligned and misaligned faces (ie the composite face effect) was already of full magnitude at the smallest level of misalignment. These results imply that a small spatial misalignment is sufficient to measure the composite face effect. From a theoretical standpoint, they indicate that it is the breaking of a whole configuration rather than the increase in relative distance between the face parts that explains the presence or absence of the composite face effect, clarifying an outstanding issue concerning the nature of holistic face perception.

CognitiveTask

PRP

10.3758/s13414-013-0615-x

Attention, perception & psychophysics

Atten Percept Psychophys

Orienting attention in visual working memory requires central capacity: decreased retro-cue effects under dual-task conditions.

The retro-cue effect (RCE) describes superior working memory performance for validly cued stimulus locations long after encoding has ended. Importantly, this happens with delays beyond the range of iconic memory. In general, the RCE is a stable phenomenon that emerges under varied stimulus configurations and timing parameters. We investigated its susceptibility to dual-task interference to determine the attentional requirements at the time point of cue onset and encoding. In Experiment 1, we compared single- with dual-task conditions. In Experiment 2, we borrowed from the psychological refractory period paradigm and compared conditions with high and low (dual-) task overlap. The secondary task was always binary tone discrimination requiring a manual response. Across both experiments, an RCE was found, but it was diminished in magnitude in the critical dual-task conditions. A previous study did not find evidence that sustained attention is required in the interval between cue offset and test. Our results apparently contradict these findings and point to a critical time period around cue onset and briefly thereafter during which attention is required.

CognitiveTask

PRP

10.1037/a0035548

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Exceptions to the PRP effect? A comparison of prepared and unconditioned reflexes.

Psychological research has documented again and again marked performance decrements whenever humans perform 2 or more tasks at the same time. In fact, the available evidence seems to suggest that any type of behavior is subject to such limitations. The present experiments employed the psychological refractory period (PRP) paradigm to identify a clear exception to this rule: Unconditioned reflexes do escape dual-task interference, whereas intended simple responses, so called "prepared reflexes," do not. Beyond this empirical novelty, we discuss the findings in broader terms of human action control. In particular, we suggest that the (non)susceptibility to dual-task interference may provide a clear empirical delineation between goal-directed behavior (i.e., actions) and other, not goal-directed behavior.

CognitiveTask

PRP

10.1186/1471-2202-14-122

BMC neuroscience

BMC Neurosci

Reducing multi-sensor data to a single time course that reveals experimental effects.

Multi-sensor technologies such as EEG, MEG, and ECoG result in high-dimensional data sets. Given the high temporal resolution of such techniques, scientific questions very often focus on the time-course of an experimental effect. In many studies, researchers focus on a single sensor or the average over a subset of sensors covering a "region of interest" (ROI). However, single-sensor or ROI analyses ignore the fact that the spatial focus of activity is constantly changing, and fail to make full use of the information distributed over the sensor array. We describe a technique that exploits the optimality and simplicity of matched spatial filters in order to reduce experimental effects in multivariate time series data to a single time course. Each (multi-sensor) time sample of each trial is replaced with its projection onto a spatial filter that is matched to an observed experimental effect, estimated from the remaining trials (Effect-Matched Spatial filtering, or EMS filtering). The resulting set of time courses (one per trial) can be used to reveal the temporal evolution of an experimental effect, which distinguishes this approach from techniques that reveal the temporal evolution of an anatomical source or region of interest. We illustrate the technique with data from a dual-task experiment and use it to track the temporal evolution of brain activity during the psychological refractory period. We demonstrate its effectiveness in separating the means of two experimental conditions, and in significantly improving the signal-to-noise ratio at the single-trial level. It is fast to compute and results in readily-interpretable time courses and topographies. The technique can be applied to any data-analysis question that can be posed independently at each sensor, and we provide one example, using linear regression, that highlights the versatility of the technique. The approach described here combines established techniques in a way that strikes a balance between power, simplicity, speed of processing, and interpretability. We have used it to provide a direct view of parallel and serial processes in the human brain that previously could only be measured indirectly. An implementation of the technique in MatLab is freely available via the internet.

CognitiveTask

PRP

10.1016/j.actpsy.2013.08.005

Acta psychologica

Acta Psychol (Amst)

Evidence for a response preparation bottleneck during dual-task performance: effect of a startling acoustic stimulus on the psychological refractory period.

The present study was designed to investigate the mechanism associated with dual-task interference in a psychological refractory period (PRP) paradigm. We used a simple reaction time paradigm consisting of a vocal response (R1) and key-lift task (R2) with a stimulus onset asynchrony (SOA) between 100ms and 1500ms. On selected trials we implemented a startling acoustic stimulus concurrent with the second stimulus to determine if we could involuntarily trigger the second response. Our results indicated that the PRP delay in the second response was present for both control and startle trials at short SOAs, suggesting the second response was not prepared in advance. These results support a response preparation bottleneck and can be explained via a neural activation model of preparation. In addition, we found that the reflexive startle activation was reduced in the dual-task condition for all SOAs, a result we attribute to prepulse inhibition associated with dual-task processing.

CognitiveTask

PRP

10.1186/2193-1801-2-368

SpringerPlus

Springerplus

Individual differences effects on the psychological refractory period.

The goal of this study was to assess the impact of individual neuropsychological differences on the ability to share attention between concurrent tasks. Participants (n = 20) were trained on six single task practice sessions and dual-task was assessed with reaction time performance on a psychological refractory period (PRP) paradigm. Neuropsychological test scores were also acquired. Furthermore, one of the known variables that can influence performances on neuropsychological tests is gender, which was added as a potential predictor. Results show that the small PRP group was associated with better performances in processing speed, inhibition, flexibility and working memory on neuropsychological tests. Gender also had an impact on the PRP, males having a lower PRP than females. A multiple regression was performed to determine which variables explained the most PRP duration, which showed that 49.1% of the variance of the PRP length could be explained by gender, reaction times of the PRP practice trials at the sixth session, the denomination and flexibility conditions of the Modified Stroop Task as well as results on the Symbol Search Test. Gender was the variable that explained the PRP variance the most (23%). Processing speed also seemed to be a great determinant of the PRP as well as the ability to alternate between task-sets as assessed by the Flexibility condition of the Modified Stroop Task. Thus, this study reveals that good performances on certain neuropsychological tests could predict one's ease to manage two tasks simultaneously with a higher chance for males to perform better.

CognitiveTask

PRP

10.1027/1618-3169/a000224

Experimental psychology

Exp Psychol

Locus of backward crosstalk effects on task 1 in a psychological refractory period task.

Our performance on a task decreases when the task is in a dual-task situation than when it is in isolation. An important experimental setting for dual-task situation is the psychological refractory period (PRP) paradigm, and the dual-task performance decrements in the PRP paradigm are referred to as PRP interference. The standard response-selection bottleneck (RSB) models state that the response-selection stage of the second task (T2) cannot start until the response-selection stage of the first task (T1) finishes, resulting in the PRP interference. Contrary to the prediction of RSB models, several researchers have found T2's modulations on T1's performance, and have suggested that T1's selection-related processes are affected by T2's selection-related processes, referred to as backward crosstalk effects. The locus of backward crosstalk effects is not clear, however, because RTs were measured in most previous studies. By using semantically unrelated stimuli and responses and by measuring T1's lateralized readiness potential, we examined the locus of backward crosstalk effects. We found that the interval between T1's stimulus onset and the stimulus-locked LRP onset was affected, suggesting T2's response selection starts before T1's selection is complete. The present result provided electrophysiological evidence focusing on T1's changes in favor of the hypothesis of parallel response selection in the PRP paradigm.

CognitiveTask

PRP

10.3758/s13414-013-0513-2

Attention, perception & psychophysics

Atten Percept Psychophys

The source of dual-task limitations: serial or parallel processing of multiple response selections?

Although it is generally recognized that the concurrent performance of two tasks incurs costs, the sources of these dual-task costs remain controversial. The serial bottleneck model suggests that serial postponement of task performance in dual-task conditions results from a central stage of response selection that can only process one task at a time. Cognitive-control models, by contrast, propose that multiple response selections can proceed in parallel, but that serial processing of task performance is predominantly adopted because its processing efficiency is higher than that of parallel processing. In the present study, we empirically tested this proposition by examining whether parallel processing would occur when it was more efficient and financially rewarded. The results indicated that even when parallel processing was more efficient and was incentivized by financial reward, participants still failed to process tasks in parallel. We conclude that central information processing is limited by a serial bottleneck.

CognitiveTask

PRP

10.1037/a0033336

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Level 2 perspective taking entails two processes: evidence from PRP experiments.

In many situations people need to mentally adopt the (spatial) perspective of other persons, an ability that is referred to as "Level 2 perspective taking." Its underlying processes have been ascribed to mental self-rotation that can be dissociated from mental object-rotation. Recent findings suggest that perspective taking/self-rotation may not require central capacity. By using the psychological refractory period (PRP) paradigm and the locus-of-slack logic, the present study scrutinized these results, ruled out alternative explanations, and extended the conclusions. In sum, the findings converge on the notion that Level 2 perspective taking entails 2 processes: a first effortless process that handles rotations of 60° or less, and a second capacity-limited process of mental self-rotation proper that is only invoked at higher degrees of required perspective taking.

CognitiveTask

PRP

10.1016/j.bbr.2013.06.013

Behavioural brain research

Behav Brain Res

Stress improves task processing efficiency in dual-tasks.

Psychological stress has attracted much interest as a potential modulator of response control processes. However, especially in dual-task situations, the effect of psychological stress is less understood. In the current study we investigated these effects. "Thirty six" healthy young male participants were exposed to stress applying the socially evaluated cold pressor task (SECPT) or a control condition. Afterwards they participated in a psychological refractory period (PRP) paradigm comprising two tasks (a "tone task" and a "letter task"). With the PRP task, four different stimulus onset asynchronies (SOA) were realized separating the tone from the letter task. The results show that stress improves task processing efficiency in dual-tasks. Stressed participants showed a reduced PRP effect (i.e., shorter response times), which was especially prominent in the short SOAs conditions (16 and 133ms). The analysis of the response times suggests that stress increases dual-tasking performance by modulating the efficiency to process the different tasks and not because 'cognitive flexibility' and switching between task components at the bottleneck is altered. Increases in processing efficiency in dual-tasks were predictable by means of individual salivary cortisol levels.

CognitiveTask

PRP

10.3758/s13414-013-0468-3

Attention, perception & psychophysics

Atten Percept Psychophys

Automatic identification of familiar faces.

Much research has suggested that facial identification has some characteristics of automaticity, in that it is rapid, nonconscious, and mandatory. However, little research has tested whether it can occur even if attention is already devoted to the demanding central processes of another task. In the present study, we addressed this type of automaticity using the psychological refractory period paradigm. In Experiments 1 and 2, participants successfully identified familiar faces, even while they were engaged with another task, indicating the automaticity of familiar-face identification. In Experiments 3 and 4, however, participants could not identify unfamiliar faces as automatically as they could identify the familiar faces. We concluded that automatic face identification is possible, but dependent on prior familiarity.

CognitiveTask

PRP

10.1177/0956797612471540

Psychological science

Psychol Sci

General cognitive ability and the psychological refractory period: individual differences in the mind's bottleneck.

Identifying the precise locus of general cognitive ability (g) in the flow of information between perception and action is an important goal of differential psychology. To localize the negative correlation between g and reaction time to a specific processing stage, we administered a speeded number-comparison task to two groups differing in average g. The participants had to respond to two stimuli in each trial, which produced the well-known slowing of the second reaction time known as the psychological refractory period. The difference in the second reaction time favoring the high-g group doubled as the stimulus onsets became very close together. This finding affirms that the faster reaction times of higher-g individuals reflect an advantage exclusively in the serial bottleneck of central processing and not in the parallel peripheral stages.

CognitiveTask

PRP

10.1016/j.bbr.2013.05.010

Behavioural brain research

Behav Brain Res

Dual-task performance is differentially modulated by rewards and punishments.

Dual-task situations play a pivotal role in daily life and are subject to a research in cognitive psychology and neuroscience. From a neuroscience perspective, the response selection bottleneck may be partly constituted by the dopaminergic system. The dopaminergic system plays a pivotal role in reward and punishment effects. In the current study we therefore investigated the effects of rewards and punishments as a potential modulator of dual-tasking processes. We examined dual-task performance in the psychological refractory period (PRP) paradigm, where the task order was either predictable, or unpredictable. Three groups were tested; a punishment group (N=14), a reward group (N=18) and a control group (N=16). The results show that in the punishment condition, dual-task performance is increased relative to controls (i.e., faster RTs). In the reward condition performance decreased relative to controls. The effects observed were of moderate to high effect sizes. However, the effects were only evident when task performance was unpredictable. These divergent effects of rewards and punishments on dual-tasking may be explained by the differential involvement of different dopamine receptors in rewards and punishments, and their effects on the amount and flexibility of task goals in working memory.

CognitiveTask

PRP

10.3389/fncom.2013.00055

Frontiers in computational neuroscience

Front Comput Neurosci

Interfacing sensory input with motor output: does the control architecture converge to a serial process along a single channel?

Modular organization in control architecture may underlie the versatility of human motor control; but the nature of the interface relating sensory input through task-selection in the space of performance variables to control actions in the space of the elemental variables is currently unknown. Our central question is whether the control architecture converges to a serial process along a single channel? In discrete reaction time experiments, psychologists have firmly associated a serial single channel hypothesis with refractoriness and response selection [psychological refractory period (PRP)]. Recently, we developed a methodology and evidence identifying refractoriness in sustained control of an external single degree-of-freedom system. We hypothesize that multi-segmental whole-body control also shows refractoriness. Eight participants controlled their whole body to ensure a head marker tracked a target as fast and accurately as possible. Analysis showed enhanced delays in response to stimuli with close temporal proximity to the preceding stimulus. Consistent with our preceding work, this evidence is incompatible with control as a linear time invariant process. This evidence is consistent with a single-channel serial ballistic process within the intermittent control paradigm with an intermittent interval of around 0.5 s. A control architecture reproducing intentional human movement control must reproduce refractoriness. Intermittent control is designed to provide computational time for an online optimization process and is appropriate for flexible adaptive control. For human motor control we suggest that parallel sensory input converges to a serial, single channel process involving planning, selection, and temporal inhibition of alternative responses prior to low dimensional motor output. Such design could aid robots to reproduce the flexibility of human control.

CognitiveTask

PRP

10.3758/s13423-013-0438-8

Psychonomic bulletin & review

Psychon Bull Rev

Lost ability to automatize task performance in old age.

Can elderly adults automatize a new task? To address this question, 10 older adults each performed 10,080 training trials over 12 sessions on an easy but novel task. The psychological refractory period (PRP) procedure was then used to evaluate whether this highly practiced task, when presented as task 2 along with an unpracticed task 1, could proceed automatically. If automatic, task 2 processing should bypass the bottleneck and, therefore, not be delayed while central attention is devoted to task 1, yielding little dual-task interference. This is exactly what Maquestiaux, Laguë-Beauvais, Ruthruff, and Bherer (Memory and Cognition 36:1262-1282, 2008) previously observed for almost all younger adults, even with half the training on a more difficult task. Although extensive training reduced older adults' reaction times to only 307 ms, a value virtually identical to that attained by Maquestiaux et al.'s (Memory and Cognition 36:1262-1282, 2008) younger adults, the highly practiced task 2 was slowed by 485 ms in the dual-task PRP procedure. Such a large slowing in older adults is striking given the easy tasks and massive amounts of practice. These findings demonstrate a qualitative change with age, in which older adults lose the ability to automatize novel tasks, which cannot be attributed merely to generalized cognitive slowing.

CognitiveTask

PRP

10.3758/s13414-013-0457-6

Attention, perception & psychophysics

Atten Percept Psychophys

Information continuity across the response selection bottleneck: early parallel Task 2 response activation contributes to overt Task 2 performance.

Several studies of dual-task performance have demonstrated Task 2 to Task 1 response priming (backward compatibility effects), indicating some degree of parallel response computation for concurrent tasks and suggesting that the well-established response selection bottleneck (RSB) model may be incomplete. However, the RSB might be considered to remain informationally intact if this early parallel Task 2 response information does not persist across the attentional shift between tasks to contribute to overt Task 2 performance. We used an adapted psychological refractory period paradigm with an additional early transient Task 2 stimulus to examine whether response information generated for Task 2 in parallel with overt Task 1 response selection could persist across the bottleneck to influence eventual overt Task 2 performance. After controlling for potential indirect effects of Task 1 processing stage variability propagating onto Task 2 reaction time via locus of slack effects, we observed reliable and consistent effects of early Task 2 response information facilitating Task 2 reaction times. These effects were observed only when the responses to both tasks of the dual-task pair were compatible, under both univalent and bivalent response mappings across tasks. These findings may represent evidence of a variably sensitive response gating or suppression mechanism in dual-task performance and support the idea that backward response compatibility effects represent transient informational influences on central response codes, rather than later postbottleneck response execution processes.

CognitiveTask

PRP

10.1167/13.3.4

Journal of vision

J Vis

Freedom and rules in human sequential performance: a refractory period in eye-hand coordination.

In action sequences, the eyes and hands ought to be coordinated in precise ways. The mechanisms governing the architecture of encoding and action of several effectors remain unknown. Here we study hand and eye movements in a sequential task in which letters have to be typed while they move down through the screen. We observe a strict refractory period of about 200 ms between the initiation of manual and eye movements. Subjects do not initiate a saccade just after typing and do not type just after making the saccade. This refractory period is observed ubiquitously in every subject and in each step of the sequential task, even when keystrokes and saccades correspond to different items of the sequence-for instance when a subject types a letter that has been gazed at in a preceding fixation. These results extend classic findings of dual-task paradigms, of a bottleneck tightly locked to the response selection process, to unbounded serial routines. Interestingly, while the bottleneck is seemingly inevitable, better performing subjects can adopt a strategy to minimize the cost of the bottleneck, overlapping the refractory period with the encoding of the next item in the sequence.

CognitiveTask

PRP

10.1142/S0219635212500252

Journal of integrative neuroscience

J Integr Neurosci

When order matters: last-come first-served effect in sequential arithmetic operations.

Cognitive psychologists have relied on dual-task interference experiments to understand the low-capacity and serial nature of conscious mental operations. Two widely studied paradigms, the Attentional Blink (AB) and the Psychological Refractory Period (PRP) have demonstrated a first-come first-served policy; processing a stimulus either impedes conscious access (AB) or postpones treatment (PRP) of a concurrent stimulus. Here we explored the transition from dual-task paradigms to multi-step human cognition. We studied the relative weight of individual addends in a sequential arithmetic task, where number notation (symbolic/non-symbolic) and presentation speed were independently manipulated. For slow presentation and symbolic notation, the decision relied almost equally on all addends, whereas for fast or non-symbolic notation, the decision relied almost exclusively on the last item reflecting a last-come first-served policy. We suggest that streams of stimuli may be chunked in events in which the last stimuli may override previous items from sensory buffers.

CognitiveTask

PRP

10.1371/journal.pcbi.1002843

PLoS computational biology

PLoS Comput Biol

Refractoriness in sustained visuo-manual control: is the refractory duration intrinsic or does it depend on external system properties?

Researchers have previously adopted the double stimulus paradigm to study refractoriness in human neuromotor control. Currently, refractoriness, such as the Psychological Refractory Period (PRP) has only been quantified in discrete movement conditions. Whether refractoriness and the associated serial ballistic hypothesis generalises to sustained control tasks has remained open for more than sixty years. Recently, a method of analysis has been presented that quantifies refractoriness in sustained control tasks and discriminates intermittent (serial ballistic) from continuous control. Following our recent demonstration that continuous control of an unstable second order system (i.e. balancing a 'virtual' inverted pendulum through a joystick interface) is unnecessary, we ask whether refractoriness of substantial duration (~200 ms) is evident in sustained visual-manual control of external systems. We ask whether the refractory duration (i) is physiologically intrinsic, (ii) depends upon system properties like the order (0, 1(st), and 2(nd)) or stability, (iii) depends upon target jump direction (reversal, same direction). Thirteen participants used discrete movements (zero order system) as well as more sustained control activity (1(st) and 2(nd) order systems) to track unpredictable step-sequence targets. Results show a substantial refractory duration that depends upon system order (250, 350 and 550 ms for 0, 1(st) and 2(nd) order respectively, n=13, p<0.05), but not stability. In sustained control refractoriness was only found when the target reverses direction. In the presence of time varying actuators, systems and constraints, we propose that central refractoriness is an appropriate control mechanism for accommodating online optimization delays within the neural circuitry including the more variable processing times of higher order (complex) input-output relations.

CognitiveTask

PRP

10.1080/17470218.2012.752019

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Ageing and attentional control.

The research examines the structural bottleneck account and the resource account of the substantial dual-task deficits among older adults. Procedures from two common dual-task methodologies-the psychological refractory period and the relative-priority manipulation-were used to encourage maximization of the joint performance. Performance and time-sharing strategies from subjects between the ages of 20 and 70 years were examined. Age-related declines in time-sharing efficiency and in the precision of the executive control process were observed. The age-related effect was larger when two manual responses were required than when one manual and one vocal response were required, but no evidence for obligatory sequential processing was found. Except for the most demanding conditions, comparable practice effects were observed between the younger and older subjects, suggesting considerable cognitive plasticity in the older subjects. Implications for the two attentional accounts were discussed.

CognitiveTask

PRP

10.1037/a0030431

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Multiple bottlenecks in hierarchical control of action sequences: what does "response selection" select in skilled typewriting?

Does response selection select words or letters in skilled typewriting? Typing performance involves hierarchically organized control processes: an outer loop that controls word level processing, and an inner loop that controls letter (or keystroke) level processing. The present study addressed whether response selection occurs in the outer loop or the inner loop by using the psychological refractory period (PRP) paradigm in which Task1 required typing single words and Task2 required vocal responses to tones. The number of letters (string length) in the words was manipulated to discriminate selection of words from selection of keystrokes. In Experiment 1, the PRP effect depended on string length of words in Task1, suggesting that response selection occurs in the inner loop. To assess contributions of the outer loop, the influence of string length was examined in a lexical-decision task that also involves word encoding and lexical access (Experiment 2), or to-be-typed words were preexposed so outer-loop processing could finish before typing started (Experiment 3). Response time for Task2 (RT2) did not depend on string length with lexical decision, and RT2 still depended on string length with typing preexposed strings. These results support the inner-loop locus of the PRP effect. In Experiment 4, typing was performed as Task2, and the effect of string length on typing RT interacted with stimulus onset asynchrony superadditively, implying that another bottleneck also exists in the outer loop. We conclude that there are at least two bottleneck processes in skilled typewriting.

CognitiveTask

PRP

10.1037/a0030296

Neuropsychology

Neuropsychology

Constraints on information processing capacity in adults with ADHD.

Researchers in the cognitive sciences have demonstrated the existence of processing capacity bottlenecks in the human brain. These capacity bottlenecks restrict our ability to process and act on environmental information. The purpose of the current study was to examine whether adults with attention-deficit hyperactivity disorder (ADHD) show reduced capacity of working memory and response selection mechanisms. Thirty-eight young adults with ADHD and 33 comparison adults were assessed using two measures of processing capacity. A dual choice-response task (psychological refractory period [PRP] task) measured response selection capacity, and an n-back task measured working memory capacity. These tasks measured capacity by assessing the degree to which increasing processing load disrupted performance. Results confirmed that performance declined as cognitive load was increased, and this was true for both groups on each task. On the PRP task, the performance decline resulting from increased cognitive load was more pronounced in the ADHD group than in the control group, indicative of reduced response selection capacity in the ADHD group. On the n-back task, however, there was no group difference in the degree to which increasing processing load disrupted performance. Results indicate that adults with ADHD show a specific capacity reduction of response selection. This evidence suggests a dissociation between working memory and response selection capacities, and it may have implications for understanding cognitive dysfunction in adults with ADHD.

CognitiveTask

PRP

10.1016/j.aap.2012.08.016

Accident; analysis and prevention

Accid Anal Prev

Mitigating the effects of in-vehicle distractions through use of the Psychological Refractory Period paradigm.

Modern driving involves frequent and potentially detrimental interactions with distracting in-vehicle tasks. Distraction has been shown to slow brake reaction time and decrease lateral and longitudinal vehicle control. It is likely that these negative effects will become more prevalent in the future as advances are made in the functionality, availability, and number of in-vehicle systems. This paper addresses this problem by considering ways to manage in-vehicle task presentation to mitigate their distracting effects. A driving simulator experiment using 48 participants was performed to investigate the existence of the Psychological Refractory Period in the driving context and its effect on braking performance. Drivers were exposed to lead vehicle braking events in isolation (single-task) and with a preceding surrogate in-vehicle task (dual-task). In dual-task scenarios, the time interval between the in-vehicle and braking tasks was manipulated. Brake reaction time increased when drivers were distracted. The in-vehicle task interfered with the performance of the braking task in a manner that was dependent on the interval between the two tasks, with slower reactions following a shorter inter-task interval. This is the Psychological Refractory Period effect. These results have implications for driver safety during in-vehicle distraction. The findings are used to develop recommendations regarding the timing of in-vehicle task presentation so as to reduce their potentially damaging effects on braking performance. In future, these guidelines could be incorporated into a driver workload management system to minimise the opportunity for a driver to be distracted from the ongoing driving task.

CognitiveTask

PRP

10.3389/fpsyg.2012.00316

Frontiers in psychology

Front Psychol

Pupil dilation: a fingerprint of temporal selection during the "attentional blink".

Pupil dilation indexes cognitive events of behavioral relevance, like the storage of information to memory and the deployment of attention. Yet, given the slow temporal response of the pupil dilation, it is not known from previous studies whether the pupil can index cognitive events in the short time scale of ∼100 ms. Here we measured the size of the pupil in the Attentional Blink (AB) experiment, a classic demonstration of attentional limitations in processing rapidly presented stimuli. In the AB, two targets embedded in a sequence have to be reported and the second stimulus is often missed if presented between 200 and 500 ms after the first. We show that pupil dilation can be used as a marker of cognitive processing in AB, revealing both the timing and amount of cognitive processing. Specifically, we found that in the time range where the AB is known to occur: (i) the pupil dilation was delayed, mimicking the pattern of response times in the Psychological Refractory Period (PRP) paradigm, (ii) the amplitude of the pupil was reduced relative to that of larger lags, even for correctly identified targets, and (iii) the amplitude of the pupil was smaller for missed than for correctly reported targets. These results support two-stage theories of the Attentional Blink where a second processing stage is delayed inside the interference regime, and indicate that the pupil dilation can be used as a marker of cognitive processing in the time scale of ∼100 ms. Furthermore, given the known relation between the pupil dilation and the activity of the locus coeruleus, our results also support theories that link the serial stage to the action of a specific neuromodulator, norepinephrine.

CognitiveTask

PRP

10.3389/fnint.2012.00075

Frontiers in integrative neuroscience

Front Integr Neurosci

The effect of task order predictability in audio-visual dual task performance: Just a central capacity limitation?

In classic Psychological-Refractory-Period (PRP) dual-task paradigms, decreasing stimulus onset asynchronies (SOA) between the two tasks typically lead to increasing reaction times (RT) to the second task and, when task order is non-predictable, to prolonged RTs to the first task. Traditionally, both RT effects have been advocated to originate exclusively from the dynamics of a central bottleneck. By focusing on two specific electroencephalographic brain responses directly linkable to perceptual or motor processing stages, respectively, the present study aimed to provide a more detailed picture as to the origin(s) of these behavioral PRP effects. In particular, we employed 2-alternative forced-choice (2AFC) tasks requiring participants to identify the pitch of a tone (high versus low) in the auditory, and the orientation of a target object (vertical versus horizontal) in the visual, task, with task order being either predictable or non-predictable. Our findings show that task order predictability (TOP) and inter-task SOA interactively determine the speed of (visual) perceptual processes (as indexed by the PCN timing) for both the first and the second task. By contrast, motor response execution times (as indexed by the LRP timing) are influenced independently by TOP for the first, and SOA for the second, task. Overall, this set of findings complements classical as well as advanced versions of the central bottleneck model by providing electrophysiological evidence for modulations of both perceptual and motor processing dynamics that, in summation with central capacity limitations, give rise to the behavioral PRP outcome.

CognitiveTask

PRP

10.3389/fnint.2012.00060

Frontiers in integrative neuroscience

Front Integr Neurosci

Electrophysiological evidence for adult age-related sparing and decrements in emotion perception and attention.

The present study examined adult age differences in processing emotional faces using a psychological refractory period paradigm. We used both behavioral and event-related potential (P1 component) measures. Task 1 was tone discrimination (fuzzy vs. pure tones) and Task 2 was emotional facial discrimination ("happy" vs. "angry" faces). The stimulus onset asynchrony (SOA) between the two tasks was 100, 300, and 900 ms. Earlier research observed larger age deficits in emotional facial discrimination for negative (angry) than for positive (happy) faces (Baena et al., 2010). Thus, we predicted that older adults would show decreased attentional efficiency in carrying out dual-task processing on the P1 (a component linked to amygdalar modulation of visual perception; Rotshtein et al., 2010). Both younger and older groups showed significantly higher P1 amplitudes at 100- and 300-ms SOAs than at the 900-ms SOA, and this suggests that both age groups could process Task 2 faces without central attention. Also, younger adults showed significantly higher P1 activations for angry than for happy faces, but older adults showed no difference. These results are consistent with the idea that younger adults exhibited amygdalar modulation of visual perception, but that older adults did not.

CognitiveTask

PRP

10.1016/j.cub.2012.07.043

Current biology : CB

Curr Biol

Decision making during the psychological refractory period.

In spite of its massively parallel architecture [1], the human brain is fundamentally limited if required to perform two tasks at the same time [2, 3]. This limitation can be studied with the psychological refractory period (PRP) paradigm, where two stimuli that require speeded responses occur in close succession [4]. Interference generally takes the form of a delay in the time to respond to the second stimulus [5]. Previous studies suggested that sensory decisions require the accumulation of sensory evidence [6, 7] and that the PRP reflects the inability to form more than one decision at a time [4, 8]. In the present study, we used a psychophysical reverse-correlation technique [9, 10] to measure the time-course of evidence accumulation during the PRP. We found that the accumulation of evidence could occur during the PRP albeit with a reduced efficiency, which implies that multiple decision processes can occur in parallel in the human brain. In addition to the reduced efficiency of evidence accumulation, our results uncover an additional delay in the routing of the decision to motor structures during the PRP, which implies that the process of sensory decision making is separable from the preparation of a motor response [11-13].

CognitiveTask

PRP

10.3758/s13428-012-0244-7

Behavior research methods

Behav Res Methods

Assessing the evidence for response time mixture distributions.

I describe a technique for comparing two simple accounts of a distribution of response times: A mixture model and a generalized-shift model. In the mixture model, a target distribution is assumed to be a mixture of response times from two other (reference) distributions. In the generalized-shift model, the target distribution is assumed to be a quantile average of the reference distributions. In order to distinguish these two possibilities, quantiles for the target distribution are estimated from the quantiles of the reference distributions assuming either a shift or a mixture, and the predicted quantiles are used to calculate the multinomial likelihood of the obtained data. Monte Carlo simulations reported here demonstrate that the index is relatively unbiased, is effective with moderate sample sizes and modest spreads between the reference distributions, is relatively unaffected by changes in the number of bins or by data trimming, can be used with data aggregated across subjects, and is relatively insensitive to a range of subject variations in distribution shape and in mixture or shift proportion. As an illustration, the index is applied to the interpretation of three effects from distinct paradigms: residual switch costs in the task-switching paradigm, the psychological refractory period effect, and sequential effects in the Simon task. I conclude that the multinomial likelihood index provides a useful and easily applied tool for the interpretation of effects on response time distributions.

CognitiveTask

PRP