Datasets:

morteza

/

cogtext

like 0

10.1016/j.ijpsycho.2012.06.005

International journal of psychophysiology : official journal of the International Organization of Psychophysiology

Int J Psychophysiol

Electrophysiological evidence of multitasking impairment of attentional deployment reflects target-specific processing, not distractor inhibition.

We studied the interaction between the control mechanisms subserving spatial attention and central attention using the psychological refractory period (PRP) paradigm. Two stimuli, a pure tone (T(1)) and a circular visual array (T(2)), including a salient target and a salient distractor, were presented at varying stimulus onset asynchronies, each requiring a speeded response. Target-specific and distractor-specific lateralized event-related potentials were isolated by placing one of them at a lateral position and the other on the vertical midline. As SOA was decreased, a progressive reduction and postponement of a T(2)-locked N2pc component was observed with a lateral target and a central distractor. No lateralized potentials were associated with a lateral distractor and a central target. The sustained posterior contralateral negativity (SPCN) was observed independently of SOA modulation, only with a lateral target. We also observed an earlier positive deflection, the Ppc (positivity posterior contralateral), that was contralateral to both lateral targets and distractors, whose amplitude and latency were not affected by SOA variations. We conclude that central processing interferes specifically with target processing reflected by the N2pc and SPCN. We propose that the Ppc reflects an initial, bottom-up response to the presence of a salient stimulus, whereas the N2pc and SPCN reflect the controlled deployment of spatial attention to targets and maintenance of target information in visual short-term memory, respectively.

CognitiveTask

PRP

10.1111/j.1469-8986.2012.01391.x

Psychophysiology

Psychophysiology

The role of sustained posterior brain activity in the serial chaining of two cognitive operations: a MEG study.

A fundamental necessity in human cognition is to link sequential mental operations where appropriate execution of the second task requires input from the first. The present study explores the neural basis of such "chaining" using a novel psychological refractory period (PRP) task. Participants were required to make speeded responses to two sequential visual tasks that were chained or independent. Magnetoencephalography (MEG) signals were recorded simultaneously to reveal the brain's response to these similar but fundamentally different conditions. RTs to Task 1 and 2 were slower in the Chained condition, and their temporal coupling weakened, relative to the Independent condition. MEG analysis of the accompanying event-related fields (ERFs) revealed an increased sustained posterior component in the Chained condition beginning approximately 350 ms after Task 2 onset and lasting for 450 ms. Beamformer localization of this ERF effect revealed a left hemisphere source near the junction of the temporal, parietal, and occipital lobes. These results extend our understanding of the behavioral and corresponding neural mechanisms required by everyday decision making.

CognitiveTask

PRP

10.3758/s13415-012-0094-x

Cognitive, affective & behavioral neuroscience

Cogn Affect Behav Neurosci

Electrodermal responses to sources of dual-task interference.

There is a response selection bottleneck that is responsible for dual-task interference. How the response selection bottleneck operates was addressed in three dual-task experiments. The overlap between two tasks (as indexed by the stimulus onset asynchrony [SOA]) was systematically manipulated, and both reaction time and electrodermal activity were measured. In addition, each experiment also manipulated some aspect of the difficulty of either task. Both increasing task overlap by reducing SOA and increasing the difficulty of either task lengthened reaction times. Electrodermal response was strongly affected by task difficulty but was only weakly affected by SOA, and in a different manner from reaction time. A fourth experiment found that the subjectively perceived difficulty of a dual-task trial was affected both by task difficulty and by SOA, but in different ways than electrodermal activity. Overall, the results were not consistent with a response selection bottleneck that involves processes of voluntary, executive attention. Instead, the results converge with findings from neural network modeling to suggest that the delay of one task while another is being processed reflects the operation of a routing mechanism that can process only one stream of information for action at a time and of a passive, structural store that temporarily holds information for the delayed task. The results suggest that conventional blocked or event-related neuroimaging designs may be inadequate to identify the mechanism of operation of the response selection bottleneck.

CognitiveTask

PRP

10.1016/j.cortex.2012.03.014

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

Cortex

Splitting of the P3 component during dual-task processing in a patient with posterior callosal section.

When two concurrent sensorimotor tasks have to be performed at a short time interval, the second response is generally delayed at a central decision stage. However, in patients who have undergone full or partial transection of forebrain fibers connecting the two hemispheres (split-brain), independent structures subserving all processing stages should reside in each disconnected hemisphere, thus predicting parallel processing of dual tasks. Surprisingly, this prediction is usually not verified behaviorally. We reasoned that brain imaging with high-density recordings of event-related potentials (ERPs) could clarify the extent and limits of parallel processing in callosal patients. We studied a patient (AC) with posterior callosal section in a lateralized number-comparison task. Behaviorally, the split-brain patient showed robust dual-task interference, superficially similar to the psychological refractory period (PRP) effect in the control group of 14 healthy subjects, but significantly different in important aspects such as slowing of response times in the first task. Analysis of ERPs revealed that the parietal P3 component became split into distinct contralateral components in the patient, and was dramatically reduced for targets in his left visual field. In contrast to the control group, P3 latencies showed minimal to nonexistent postponement related to dual-task processing in the patient. In summary, our findings suggest that the left and right hemisphere networks normally involved in a single distributed "global neuronal workspace" that underlies the generation of the P3 component and serial processing, became strongly decoupled after a posterior callosal lesion.

CognitiveTask

PRP

10.1080/87565641.2011.632459

Developmental neuropsychology

Dev Neuropsychol

Multiple task interference is greater in children with ADHD.

There is considerable lay discussion that children with attention deficit hyperactivity disorder (ADHD) have increased difficulty with multitasking, but there are few experimental data. In the current study, we examine the simultaneous processing of two stimulus-response tasks using the Psychological Refractory Period (PRP) effect. We hypothesized that children with ADHD would show a greater PRP effect, suggesting a prolonged "bottleneck" in stimulus-response processing. A total of 19 school-aged children with ADHD showed a prolonged PRP effect compared with 25 control children, suggesting a higher cognitive cost in ADHD for multitasking.

CognitiveTask

PRP

10.3758/s13423-011-0190-x

Psychonomic bulletin & review

Psychon Bull Rev

Semantic picture-word interference is a postperceptual effect.

Naming a picture is slower while ignoring a semantically related versus an unrelated distractor word (semantic picture-word interference, or PWI). To locate the PWI effect in the word production processing stream (during perceptual encoding, response selection, or afterward), we used the psychological refractory period paradigm, in which participants identified a tone and then, at varying SOAs, named a picture while ignoring a semantically related or unrelated word (following Dell'Acqua, Job, Peressotti, & Pascali, 2007). As in results from the Stroop paradigm (Fagot & Pashler, 1992), we found equivalent PWI effects at short and long SOAs following tone identification in two experiments, indicating that semantic competition occurs at response selection or later. Our results suggest that it is premature to assume that competitive selection occurs at multiple levels in the word production system (van Maanen, van Rijn, & Borst, 2009) or that the Stroop and semantic PWI effects are fundamentally different (Dell'Acqua et al., 2007).

CognitiveTask

PRP

10.1111/j.1551-6709.2011.01213.x

Cognitive science

Cogn Sci

RACE/A: an architectural account of the interactions between learning, task control, and retrieval dynamics.

This article discusses how sequential sampling models can be integrated in a cognitive architecture. The new theory Retrieval by Accumulating Evidence in an Architecture (RACE/A) combines the level of detail typically provided by sequential sampling models with the level of task complexity typically provided by cognitive architectures. We will use RACE/A to model data from two variants of a picture-word interference task in a psychological refractory period design. These models will demonstrate how RACE/A enables interactions between sequential sampling and long-term declarative learning, and between sequential sampling and task control. In a traditional sequential sampling model, the onset of the process within the task is unclear, as is the number of sampling processes. RACE/A provides a theoretical basis for estimating the onset of sequential sampling processes during task execution and allows for easy modeling of multiple sequential sampling processes within a task.

CognitiveTask

PRP

10.1037/a0026315

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

The locus of tool-transformation costs.

Transformations of hand movements by tools such as levers or electronic input devices can invoke performance costs compared to untransformed movements. This study investigated by means of the Psychological Refractory Period (PRP) paradigm at which stage of information processing such tool-transformation costs arise. We used an inversion transformation, that is, the movement of the operating hand was transformed into a spatially incompatible movement of a lever. As a basic tool-transformation effect, the initiation of inverted tool movements was delayed compared to noninverted movements. Experiment 1 suggested a central (or postcentral) locus of this tool-transformation effect and ruled out a (precentral) perceptual locus. Experiments 2 and 3 confirmed the central locus and ruled out a later, motor-related stage of processing. The results show that spatially incompatible tool movements delay a capacity-limited stage of information processing, often referred to as response selection.

CognitiveTask

PRP

10.1037/a0026136

Experimental and clinical psychopharmacology

Exp Clin Psychopharmacol

Effects of energy drinks mixed with alcohol on information processing, motor coordination and subjective reports of intoxication.

The consumption of alcohol mixed with energy drinks (AmED) has become a popular and controversial practice among young people. Increased rates of impaired driving and injuries have been associated with AmED consumption. The purpose of this study was to examine if the consumption of AmED alters cognitive processing and subjective measures of intoxication compared with the consumption of alcohol alone. Eighteen participants (nine men and nine women) attended four test sessions where they received one of four doses in random order (0.65 g/kg alcohol, 3.57 ml/kg energy drink, AmED, or a placebo beverage). Performance on a psychological refractory period (PRP) task was used to measure dual-task information processing and performance on the Purdue pegboard task was used to measure simple and complex motor coordination following dose administration. In addition, various subjective measures of stimulation, sedation, impairment, and level of intoxication were recorded. The results indicated that alcohol slowed dual-task information processing and impaired simple and complex motor coordination. The coadministration of the energy drink with alcohol did not alter the alcohol-induced impairment on these objective measures. For subjective effects, alcohol increased various ratings indicative of feelings of intoxication. More importantly, coadministration of the energy drink with alcohol reduced perceptions of mental fatigue and enhanced feelings of stimulation compared to alcohol alone. In conclusion, AmED may contribute to a high-risk scenario for a drinker. The mix of behavioral impairment with reduced fatigue and enhanced stimulation may lead AmED consumers to erroneously perceive themselves as better able to function than is actually the case.

CognitiveTask

PRP

10.1016/j.neuroimage.2011.09.063

NeuroImage

Neuroimage

A shared cortical bottleneck underlying Attentional Blink and Psychological Refractory Period.

Doing two things at once is difficult. When two tasks have to be performed within a short interval, the second is sharply delayed, an effect called the Psychological Refractory Period (PRP). Similarly, when two successive visual targets are briefly flashed, people may fail to detect the second target (Attentional Blink or AB). Although AB and PRP are typically studied in very different paradigms, a recent detailed neuromimetic model suggests that both might arise from the same serial stage during which stimuli gain access to consciousness and, as a result, can be arbitrarily routed to any other appropriate processor. Here, in agreement with this model, we demonstrate that AB and PRP can be obtained on alternate trials of the same cross-modal paradigm and result from limitations in the same brain mechanisms. We asked participants to respond as fast as possible to an auditory target T1 and then to a visual target T2 embedded in a series of distractors, while brain activity was recorded with magneto-encephalography (MEG). For identical stimuli, we observed a mixture of blinked trials, where T2 was entirely missed, and PRP trials, where T2 processing was delayed. MEG recordings showed that PRP and blinked trials underwent identical sensory processing in visual occipito-temporal cortices, even including the non-conscious separation of targets from distractors. However, late activations in frontal cortex (>350 ms), strongly influenced by the speed of task-1 execution, were delayed in PRP trials and absent in blinked trials. Our findings suggest that PRP and AB arise from similar cortical stages, can occur with the same exact stimuli, and are merely distinguished by trial-by-trial fluctuations in task processing.

CognitiveTask

PRP

10.1162/jocn_a_00149

Journal of cognitive neuroscience

J Cogn Neurosci

On the automaticity of semantic processing during task switching.

There is growing evidence that processes formerly believed to be automatic are, in fact, strongly modulated by top-down influences. The purpose of the present work was to investigate how cognitive control can affect the purported automaticity of word processing by examining the impact of task switching on semantic processing using the ERP technique. In the context of the psychological refractory period dual-task paradigm, two experiments contrasted the context-sensitive N400 ERP elicited by the second of two target words under conditions that involved either a task switch or no-task switch. Although the N400 was not affected by SOA in the absence of switching, it was strongly attenuated at short SOAs when the psychological refractory period procedure involved a switch from a perceptual to a semantic task (Experiment 1) or a switch between two different semantic tasks (Experiment 2). These findings suggest that semantic processing cannot be performed in parallel with task switching and illustrate limitations in the ability of the cognitive system to adapt flexibly to the dynamically changing challenges of the environment according to task demands and behavioral goals.

CognitiveTask

PRP

10.1007/s00426-011-0375-y

Psychological research

Psychol Res

The cost of serially chaining two cognitive operations.

As Turing (1936, Proceedings of the London Mathematical Society) noted, a fundamental process in human cognition is to effect chained sequential operations in which the second operation requires an input from the preceding one. Although a great deal is known about the costs associated with 'independent' (unrelated) operations, e.g., from the classic psychological refractory period paradigm, far less is known about those operations to which Turing referred. We present the results of two behavioural experiments, where participants were required to perform two speeded sequential tasks that were either chained or independent. Both experiments reveal the reaction time cost of chaining, over and above classical dual-task serial costs. Moreover, the chaining operation significantly altered the distribution of reaction times relative to the Independent condition in terms of an increased mean and variance. These results are discussed in terms of the cognitive architecture underlying the serial chaining of cognitive operations.

CognitiveTask

PRP

10.1007/s00426-011-0368-x

Psychological research

Psychol Res

Interference effects of stimulus-response modality pairings in dual tasks and their robustness.

Recent evidence suggests that the degree of interference in dual-task situations depends crucially on the pairings of input- and output modalities of the two component tasks with increased dual-task costs for modality incompatible (i.e., visual-vocal and auditory-manual) compared to modality compatible (i.e., visual-manual and auditory-vocal) dual tasks. These effects of modality pairings in dual tasks have been related to the overlap of non-preferred processing pathways in modality incompatible tasks. Until now, modality compatibility has not yet been related to other sources of interference in a dual-task context, such as stimulus-response (S-R) compatibility or crosstalk. In the present study, we conducted two experiments using the paradigm of the psychological refractory period (PRP) to test the effects of S-R compatibility and crosstalk on the effects of modality compatibility in temporally overlapping task situations. Experiment 1 revealed an overadditive interaction between stimulus onset asynchrony and modality compatibility for tasks with S-R compatible mappings, indicating that modality compatibility effects are present in different task situations, even when S-R mappings are otherwise compatible. In Experiment 2, we aimed at pinpointing the boundaries of the effects of modality compatibility in dual-task situations. We showed that additional sources of dual-task interference in a modality compatible dual task could overwrite the pronounced PRP effect previously shown for modality incompatible tasks. Taken together, these data provide new evidence that the specific types of stimulus-response modality pairings are an additional factor that might interact with other sources of interference in dual-task situations.

CognitiveTask

PRP

10.3389/fpsyg.2011.00057

Frontiers in psychology

Front Psychol

What Phonological Facilitation Tells about Semantic Interference: A Dual-Task Study.

Despite increasing interest in the topic, the extent to which linguistic processing demands attentional resources remains poorly understood. We report an empirical re-examination of claims about lexical processing made on the basis of the picture-word interference task when merged in a dual-task psychological refractory period (PRP) paradigm. Two experiments were conducted in which participants were presented with a tone followed, at varying stimulus onset asynchronies (SOAs), by a picture-word stimulus. In Experiment 1, the phonological relatedness between pictures and words was manipulated. Begin- and end-related words decreased picture naming latencies relative to unrelated words. This effect was additive with SOA effects. In Experiment 2, both the semantic and the phonological relatedness between pictures and words were manipulated. Replicating Experiment 1, effects arising from the phonological manipulation were additive with SOA effects on picture naming latencies. In contrast, effects arising from the semantic manipulation were under additive with SOA effects on picture naming latencies, that is, semantic interference decreased as SOA was decreased. Such contrastive pattern suggests that semantic and phonological effects on picture naming latencies are characterized by distinguishable sources, the former prior to the PRP bottleneck and the latter at the PRP bottleneck or after. The present findings are discussed in relation to current models of language production.

CognitiveTask

PRP

10.1080/17470218.2011.573567

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Determinants of central processing order in psychological refractory period paradigms: central arrival times, detection times, or preparation?

Three psychological refractory period (PRP) experiments were conducted to assess the effect of central arrival times at the bottleneck on task order scheduling. In Experiment 1, a visual first task (plus-minus symbol discrimination) was combined with an auditory second task (left-right tone judgement) in a standard PRP paradigm with constant task order. In Experiment 2, the order of the tasks varied unpredictably. In Experiment 3, visual-auditory dual-task trials were randomly mixed with single-task trials. To dissociate central arrival times from stimulus detection times, the perceptual stage of the visual task was extended using stimulus degradation. Most importantly, no evidence for a first-come, first-served principle at the central bottleneck was found with the employed paradigms. Instead, the results indicated that preparation (Experiment 1) and the detection times of the stimuli (Experiments 2 and 3) were the main determinants of central processing order in the present study. In the light of previous research, the results indicate that central processing order can be influenced by various factors. The interplay between these factors seems to depend highly on the conditions and requirements of the employed experimental paradigm.

CognitiveTask

PRP

10.1037/a0023918

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Stopping while going! Response inhibition does not suffer dual-task interference.

Although dual-task interference is ubiquitous in a variety of task domains, stop-signal studies suggest that response inhibition is not subject to such interference. Nevertheless, no study has directly examined stop-signal performance in a dual-task setting. In two experiments, stop-signal performance was examined in a psychological refractory period task, in which subjects inhibited one response while still executing the other. The results showed little evidence for the refractory effect in stop-signal reaction time, and stop-signal reaction time was similar in dual-task and single-task conditions, despite the fact that overt reaction times were significantly affected by dual-task interference. Therefore, the present study supports the claim that response inhibition does not suffer dual-task interference.

CognitiveTask

PRP

10.1016/j.concog.2011.04.008

Consciousness and cognition

Conscious Cogn

A PRP-study to determine the locus of target priming effects.

Visual stimuli that are made invisible by a following mask can nonetheless affect motor responses. To localize the origin of these target priming effects we used the psychological refractory period paradigm. Participants classified tones as high or low, and responded to the position of a visual target that was preceded by a prime. The stimulus onset asynchrony (SOA) between both tasks varied. In Experiment 1 the tone task was followed by the position task and SOA dependent target priming effects were observed. When the visual position task preceded the tone task in Experiment 2, with short SOA the priming effect propagated entirely to the tone task yielding faster responses to tones on visually congruent trials and delayed responses to tones on visually incongruent trials. Together, results suggest that target priming effects arise from processing before and at the level of the central bottleneck such as sensory analysis and response selection.

CognitiveTask

PRP

10.1007/s00221-011-2703-2

Experimental brain research

Exp Brain Res

How two share two tasks: evidence of a social psychological refractory period effect.

A strong assumption shared by major theoretical approaches to cognition posits that the human cognitive system has a limited capacity for information processing. Evidence supporting this claim comes from the dual-task paradigm in which one cognitive system has to process two tasks simultaneously. In this study, we examined whether bottleneck-like processing can also be elicited when a dual task is shared between two individuals. Under dual-task instructions giving priority to Task 1, we found evidence of a psychological refractory period effect in dual-task and joint-task conditions. Under equal priority instructions, we replicated the finding of a psychological refractory period effect in the dual-task, but not in the joint-task condition. These findings are in line with the assumption that a social psychological refractory period effect can be induced across two individuals. We suggest that this effect is due to task-specific monitoring requirements. We discuss our findings with respect to both dual-task and joint action theories.

CognitiveTask

PRP

10.1037/a0023095

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Attentional limits in memory retrieval-revisited.

Carrier and Pashler (1995) concluded-based on locus-of-slack dual-task methodology-that memory retrieval was subject to a central bottleneck. However, this conclusion conflicts with evidence from other lines of research suggesting that memory retrieval proceeds autonomously, in parallel with many other mental processes. In the present experiments we explored the possibility that Carrier and Pashler's conclusions were distorted by use of an experimental method unfavorable to parallel memory retrieval. New locus-of-slack experiments were performed that encouraged parallel memory retrieval strategies with instructions and feedback, along with the use of "preferred" stimulus-response modality mappings. Results from two psychological refractory period experiments showed that the effect of Task 2 recognition difficulty was consistently absorbed into cognitive slack, with both word and picture recognition. We conclude that the memory retrieval stage of recognition tasks can proceed in parallel with central operations of another task, at least under favorable conditions. Our new findings bring results from dual-task locus-of-slack methodology into agreement with other evidence that memory retrieval is not subject to severe, generic central resource limitations.

CognitiveTask

PRP

10.1016/j.actpsy.2011.03.002

Acta psychologica

Acta Psychol (Amst)

Temporal-range estimation of multiple objects: evidence for an early bottleneck.

When making parallel time-to-contact (TTC) estimates of two approaching objects, the two respective TTC estimates interfere with one another in an asymmetric fashion. The TTC of the later-arriving object is systematically overestimated, while the estimated TTC for the first-arriving object is as accurate as in a condition presenting only a single object. This asymmetric interference points to a processing bottleneck that could be due to early (e.g., during the estimation of the TTC from the optic flow) or late (e.g., during the timing of the response or the motor execution) constraints in the TTC estimation process. We used a Sperling-like prediction-motion task to differentiate between these two possibilities. Participants produced an absolute estimate of the TTC of only one of two objects approaching a target line. The target object to which the response was to be made was indicated by an auditory cue that occurred either at motion-onset or at the instant at which the two objects disappeared from the screen (occlusion-onset). The cue at motion-onset should disengage visual processing of the irrelevant stimulus. The cue at occlusion-onset, in contrast, requires visual processing of both relevant and irrelevant stimulus until occlusion. A single-object condition was introduced as a control condition. Results show symmetric interference in the motion-onset condition. In the occlusion-onset condition however, the results were congruent with asymmetric interference. Thus, the processing bottleneck in TTC estimation is originating at the earlier stages.

CognitiveTask

PRP

10.1016/j.actpsy.2011.01.016

Acta psychologica

Acta Psychol (Amst)

Processing two tasks with varying task order: central stage duration influences central processing order.

In a recent study, Sigman and Dehaene (2006, PLoS Biology, 4, 1227-1238) reported that perceptual processing duration influences processing order of two tasks in the psychological refractory period paradigm (PRP). The present study examines whether the duration of central processes also influences processing order. For this purpose, we employed letter tasks with different central processing durations and varied task order in the PRP. In one part of the experiment, a tone discrimination task was combined with a similar time-consuming letter discrimination task. In the other part, the tone task was combined with a more time-consuming letter task, which required a mental rotation of the letter thereby prolonging central processing. If the duration of central processes influences processing order, participants should perform the tone task first more often when it is presented with the more time-consuming mental rotation task, than when it is presented with the similar time-consuming letter task. The results clearly confirm this prediction and thus show that not only perceptual processing duration but also central processing duration affects processing order in a dual-task situation. We suggest that the reported effect mirrors a tendency of participants to minimize total reaction time to both tasks by reducing slack time.

CognitiveTask

PRP

10.1016/j.neuroimage.2011.03.017

NeuroImage

Neuroimage

Probing the cortical network underlying the psychological refractory period: a combined EEG-fMRI study.

Human performance exhibits strong multi-tasking limitations in simple response time tasks. In the psychological refractory period (PRP) paradigm, where two tasks have to be performed in brief succession, central processing of the second task is delayed when the two tasks are performed at short time intervals. Here, we aimed to probe the cortical network underlying this postponement of central processing by simultaneously recording electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data while 12 subjects performed two simple number-comparison tasks. Behavioral data showed a significant slowing of response times to the second target stimulus at short stimulus-onset asynchronies, together with significant correlations between response times to the first and second target stimulus, i.e., the hallmarks of the PRP effect. The analysis of EEG data showed a significant delay of the post-perceptual P3 component evoked by the second target, which was of similar magnitude as the effect on response times. fMRI data revealed an involvement of parietal and prefrontal regions in dual-task processing. The combined analysis of fMRI and EEG data-based on the trial-by-trial variability of the P3-revealed that BOLD signals in two bilateral regions in the inferior parietal lobe and precentral gyrus significantly covaried with P3 related activity. Our results show that combining neuroimaging methods of high spatial and temporal resolutions can help to identify cortical regions underlying the central bottleneck of information processing, and strengthen the conclusion that fronto-parietal cortical regions participate in a distributed "global neuronal workspace" system that underlies the generation of the P3 component and may be one of the key cerebral underpinnings of the PRP bottleneck.

CognitiveTask

PRP

10.3758/APP.72.7.1791

Attention, perception & psychophysics

Atten Percept Psychophys

Parallel response selection in dual-task situations via automatic category-to-response translation.

In contrast to the response selection bottleneck theory of dual-task performance, recent studies have demonstrated compatibility effects between secondary and primary responses on Task 1, suggesting that response information for two tasks may be generated in parallel. In two experiments, we examined the nature of Task 2 response activation in parallel with Task 1, using a psychological refractory period paradigm. Evidence of Task 2 to Task 1 response priming when each Task 2 stimulus was unique indicated that automatic parallel generation of response information occurred for Task 2 via abstract semantic category-to-response translation processes, independent of any direct stimulus-response influences. These findings are discussed in terms of their implications for the traditional response selection bottleneck theory of dual-task performance.

CognitiveTask

PRP

10.1016/j.concog.2010.09.014

Consciousness and cognition

Conscious Cogn

PRP-paradigm provides evidence for a perceptual origin of the negative compatibility effect.

Visual stimuli (primes) that are made invisible by masking can affect motor responses to a subsequent target stimulus. When a prime is followed by a mask which is followed by a target stimulus, an inverse priming effect (or negative compatibility effect) has been found: Responses are slow and frequently incorrect when prime and target stimuli are congruent, but fast and accurate when prime and target stimuli are incongruent. To functionally localize the origins of inverse priming effects, we applied the psychological refractory period (PRP-) paradigm which distinguishes a perceptual level, a central bottleneck, and a level of motor execution. Two dual-task experiments were run with the PRP-paradigm to localize the inverse priming effect relative to the central bottleneck. Together, results of the Effect-Absorption and the Effect-Propagation Procedure suggest that inverse priming effects are generated by perceptual mechanisms. We suggest two perceptual mechanisms as the source of inverse priming effects.

CognitiveTask

PRP

10.1037/a0019238

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Dual-task processing when task 1 is hard and task 2 is easy: reversed central processing order?

Five psychological refractory period (PRP) experiments were conducted with an especially time-consuming first task (Experiments 1, 3, and 5: mental rotation; Experiments 2 and 4: memory scanning) and with equal emphasis on the first task and on the second (left-right tone judgment). The standard design with varying stimulus onset asynchronies (SOAs) was extended by a condition with blocked SOAs in Experiments 3 and 4. Based on the optimization account (Miller, Ulrich, & Rolke, 2009) it was expected that participants would-at short, but not long SOAs-tend to process the relatively fast central stage of Task 2 before the time-consuming central stage of Task 1 and consequently emit the response to Task 2 before the response to Task 1. Such an optimization tendency was found, more so for the mental rotation task and for the blocked SOA condition. The results indicate that preparation, Task 1 characteristics, and TRT (total reaction time) optimization are-among others-factors influencing central processing order in PRP tasks.

CognitiveTask

PRP

10.1016/j.neuropsychologia.2010.06.034

Neuropsychologia

Neuropsychologia

Grasping for parsimony: do some motor actions escape dorsal processing?

It is an open question whether the visual transformations guiding human actions are similar to those generating visual perception. The Action-Perception model assumes a strict division of labor: the ventral cortical stream generates perception while the dorsal stream guides actions. However, only skilled and natural actions are assumed to be under dorsal control, while awkward and left-handed actions should be under ventral control in the same way as perception. Here, we used a combination of Garner-Interference and the psychological refractory period (PRP) paradigm to test this notion. We found that all types of grasping (left-handed, awkward, using a tool) behave in a way similar to skilled right-handed grasping: other than perception they show no Garner-Interference, but similar to perception they show a limitation of processing capacities as indicated by the PRP paradigm. This behavior suggests that similar processes guide all these actions.

CognitiveTask

PRP

10.1371/journal.pcbi.1000765

PLoS computational biology

PLoS Comput Biol

The brain's router: a cortical network model of serial processing in the primate brain.

The human brain efficiently solves certain operations such as object recognition and categorization through a massively parallel network of dedicated processors. However, human cognition also relies on the ability to perform an arbitrarily large set of tasks by flexibly recombining different processors into a novel chain. This flexibility comes at the cost of a severe slowing down and a seriality of operations (100-500 ms per step). A limit on parallel processing is demonstrated in experimental setups such as the psychological refractory period (PRP) and the attentional blink (AB) in which the processing of an element either significantly delays (PRP) or impedes conscious access (AB) of a second, rapidly presented element. Here we present a spiking-neuron implementation of a cognitive architecture where a large number of local parallel processors assemble together to produce goal-driven behavior. The precise mapping of incoming sensory stimuli onto motor representations relies on a "router" network capable of flexibly interconnecting processors and rapidly changing its configuration from one task to another. Simulations show that, when presented with dual-task stimuli, the network exhibits parallel processing at peripheral sensory levels, a memory buffer capable of keeping the result of sensory processing on hold, and a slow serial performance at the router stage, resulting in a performance bottleneck. The network captures the detailed dynamics of human behavior during dual-task-performance, including both mean RTs and RT distributions, and establishes concrete predictions on neuronal dynamics during dual-task experiments in humans and non-human primates.

CognitiveTask

PRP

10.1016/j.actpsy.2010.03.009

Acta psychologica

Acta Psychol (Amst)

Judging the contact-times of multiple objects: Evidence for asymmetric interference.

The accuracy of time-to-contact (TTC) judgments for single approaching objects is well researched, however, close to nothing is known about our ability to make simultaneous TTC judgments for two or more objects. Such complex judgments are required in many everyday situations, for instance when crossing a multi-lane street or when engaged in multi-player ball games. We used a prediction-motion paradigm in which participants simultaneously estimated the absolute TTC of two objects, and compared the performance to a standard single-object condition. Results showed that the order of arrival of the two objects determined the accuracy of the TTC estimates: Estimation of the first-arriving object was unaffected by the added complexity compared to the one-object condition, whereas the TTC of the second-arriving object was systematically overestimated. This result has broad implications for complex everyday situations. We suggest that it is akin to effects observed in experiments on the psychological refractory period (PRP) and that the proactive interference of the first-arriving object indicates a bottleneck or capacity sharing at the central stage.

CognitiveTask

PRP

10.1037/a0017174

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Modularity beyond perception: evidence from the PRP paradigm.

The Dimension Action (DA) model asserts that the visual system is modular, and that each task involves multiple-response mechanisms rather than a unitary-response selection mechanism. The model has been supported by evidence from single-task interference paradigms. We use the psychological refractory period paradigm and show that dual-task performance can also be explained by the DA model. In 6 experiments we contrasted predictions from the DA model with predictions from the Response Selection Bottleneck (RSB; Pashler, 1994) model asserting that dual-task limitations are due to a unitary-response selection mechanism. Task 1 in all experiments was a tone discrimination task. In Experiments 1 to 3, Task 2 was a variation of either the Stroop or the flanker tasks. Experiments 4 to 6 manipulated response selection directly. The results showed that response selection effects can be underadditive in some conditions and additive in others depending on the modular nature of the response effect. Together, the results support the existence of an underlying modular architecture as proposed by the DA model and pose serious difficulties for the RSB model.

CognitiveTask

PRP

10.1007/s00221-010-2211-9

Experimental brain research

Exp Brain Res

Does dorsal processing require central capacity? More evidence from the PRP paradigm.

The human vision system appears to divide into two streams: a ventral stream from V1 to the inferior temporal cortex processing 'vision for perception', and a dorsal stream from V1 to the posterior parietal cortex processing 'vision for action'. Among other characteristics, it has been suggested that dorsal processing is effortless, unconscious, and not bearing on central cognitive resources implicated in ventral processing. The present study shows that a typical dorsal task (i.e., grasping an object) is subject to a classical indicator of capacity limitations in dual-task situations, the psychological refractory period (PRP) effect. In particular, response times to task 2 (the grasping task) increased the more the two tasks overlapped in time, i.e., the shorter the time interval between the stimuli of the two tasks was. As is also common in PRP experiments, response times to task 1 were largely unaffected by this variation. The PRP effect was obtained despite careful control of strategic response deferment, and peripheral overlap of response modalities that may have artificially created performance costs in previous studies. Altogether, the present results show that dorsal processing is subject to the same capacity limitations that can almost universally be found with simple cognitive tasks.

CognitiveTask

PRP

10.1037/a0017122

Psychology and aging

Psychol Aging

Learning to bypass the central bottleneck: declining automaticity with advancing age.

Does advancing age reduce the ability to bypass the central bottleneck through task automatization? To answer this question, the authors asked 12 older adults and 20 young adults to first learn to perform an auditory-vocal task (low vs. high pitch) in 6 single-task sessions. Their dual-task performance was then assessed with a psychological refractory period paradigm, in which the highly practiced auditory-vocal task was presented as Task 2, along with an unpracticed visual-manual Task 1. Converging evidence indicated qualitative differences in dual-task performance with age: Whereas the vast majority of young adults bypassed the bottleneck, at most 1 of the 12 older adults was able to do so. Older adults are either reluctant to bypass the bottleneck (as a matter of strategy) or have lost the ability to automatize task performance.

CognitiveTask

PRP

10.1080/03610730903175766

Experimental aging research

Exp Aging Res

Multisession, dual-task psychological refractory period practice benefits older and younger adults equally.

The authors tested 18 younger adults and 18 older adults on four sessions in a psychological refractory period (PRP) paradigm, to see whether older adults can benefit as much from dual-task practice as younger adults. Task 1 involved tone discrimination and Task 2 involved simultaneous letter-matching. The stimulus onset asynchrony (SOA) between the tasks was either 50, 150, 300, or 900 ms. Although older adults showed a larger PRP effect than younger adults, there were no group differences in the practice/training benefit. These results differ from Maquestiaux, Hartley, and Bertsch (2004, Psychology and Aging, 19, 649-667, Experiment 1), who found that age differences in PRP effects became progressively larger with increased practice. These findings, along with the simultaneous-presentation, dual-task work of Kramer, Larish, and Strayer (1995, Journal of Experimental Psychology: Applied, 1, 50-76) and Bherer et al. (2005, Psychology and Aging, 20, 695-709; 2006, Acta Psychologica, 123, 261-278), suggest that older adults can benefit as much as younger adults from dual-task training.

CognitiveTask

PRP

10.1016/j.cognition.2010.01.003

Cognition

Cognition

Mapping introspection's blind spot: reconstruction of dual-task phenomenology using quantified introspection.

Psychologists often dismiss introspection as an inappropriate measure, yet subjects readily volunteer detailed descriptions of the time and effort that they spent on a task. Are such reports really so inaccurate? We asked subjects to perform a psychological refractory period experiment followed by extensive quantified introspection. On each trial, just after their objective responses, subjects provided no less than four subjective estimates of the timing of sensory, decision and response events. Based on these subjective variables, we reconstructed the phenomenology of an average trial and compared it to objective times and to predictions derived from the central interference model. Introspections of decision time were highly correlated with objective measures, but there was one point of drastic distortion: subjects were largely unaware that the second target was waiting while the first task was being completed, the psychological refractory period effect. Thus, conscious perception is systematically delayed and distorted while central processing resources are monopolized by another task.

CognitiveTask

PRP

10.1111/j.1756-8765.2009.01069.x

Topics in cognitive science

Top Cogn Sci

The locus of the Gratton effect in picture-word interference.

Between-trial effects in Stroop-like interference tasks are linked to differences in the amount of cognitive control. Trials following an incongruent trial show less interference, an effect suggested to result from the increased control caused by the incongruent previous trial (known as the Gratton effect). In this study, we show that cognitive control not only results in a different amount of interference but also in a different locus of the interference. That is, the stage of the task that shows the most interference changes as a function of the preceding trial. Using computational cognitive modeling, we explain these effects by a difference in the amount of processing of the irrelevant dimension of the stimulus.

CognitiveTask

PRP

10.3758/PBR.16.6.987

Psychonomic bulletin & review

Psychon Bull Rev

Stroop and picture-word interference are two sides of the same coin.

This article presents a cognitive model that reconciles a surprising observation in the picture-word interference (PWI) paradigm with the general notion that PWI is a form of Stroop interference. Dell'Acqua, Job, Peressotti, and Pascali (2007) assessed PWI using a psychological refractory period (PRP) paradigm, and concluded that the locus of interference in PWI is during the perceptual encoding stage. Stroop interference, on the other hand, is generally attributed to response selection. Based on these findings it was argued that PWI is not a Stroop effect. The present article discusses an alternative interpretation of these results. We assume that both effects are caused by the same interference mechanism, but that the processing speed associated with the different stimuli (colors vs. words) accounts for the previously reported differences. We support this argument by presenting a single computational model that accounts for both PWI and Stroop phenomena in single task and PRP settings.

CognitiveTask

PRP

10.3758/APP.71.8.1725

Attention, perception & psychophysics

Atten Percept Psychophys

The "beam of darkness": spreading of the attentional blink within and between objects.

When two targets (T1 and T2) are inserted into a rapid serial visual presentation (RSVP) stream of nontargets, observers are impaired at identifying T2 when it is presented within half a second after T1. This transient drop in performance, or attentional blink (AB), has been attributed to a temporary unavailability of task-critical processing resources. In the present study, we investigated how object-based attention modulates the AB, by presenting four synchronized RSVP streams in the corners of two rectangular bars (e.g., one above and one below fixation). The results from four experiments revealed that the AB increased within short temporal lags (of up to ~400 msec) when T2 was presented on the same, rather than a different, bar as T1 (with T1-T2 spatial distance controlled for). Thus, the AB is seen to spread across entire object groupings, suggesting that the spatiotemporal resolution of attention is modulated by global-object information.

CognitiveTask

PRP

10.1007/s00426-009-0260-0

Psychological research

Psychol Res

Late backward effects in the refractory period paradigm: effects of Task 2 execution on Task 1 performance.

The central bottleneck model assumes that in the psychological refractory paradigm, Task 1 performance is independent of Task 2 demands. Previous studies, however, have reported backward crosstalk effects of motor demands in Task 2 on Task 1 performance. These effects have been attributed to interference at the central level. The present study aimed to isolate more directly potential backward effects at the motor level. Therefore, in three experiments, movement distance in Task 2 was manipulated using a guided ballistic movement. The results showed that movement distance in Task 2 affected reaction time as well as response duration in Task 1. It is argued that the backward effect observed in this study is due to response coupling at motor rather than central levels.

CognitiveTask

PRP

10.1037/a0017187

Psychological review

Psychol Rev

Rational adaptation under task and processing constraints: implications for testing theories of cognition and action.

The authors assume that individuals adapt rationally to a utility function given constraints imposed by their cognitive architecture and the local task environment. This assumption underlies a new approach to modeling and understanding cognition-cognitively bounded rational analysis-that sharpens the predictive acuity of general, integrated theories of cognition and action. Such theories provide the necessary computational means to explain the flexible nature of human behavior but in doing so introduce extreme degrees of freedom in accounting for data. The new approach narrows the space of predicted behaviors through analysis of the payoff achieved by alternative strategies, rather than through fitting strategies and theoretical parameters to data. It extends and complements established approaches, including computational cognitive architectures, rational analysis, optimal motor control, bounded rationality, and signal detection theory. The authors illustrate the approach with a reanalysis of an existing account of psychological refractory period (PRP) dual-task performance and the development and analysis of a new theory of ordered dual-task responses. These analyses yield several novel results, including a new understanding of the role of strategic variation in existing accounts of PRP and the first predictive, quantitative account showing how the details of ordered dual-task phenomena emerge from the rational control of a cognitive system subject to the combined constraints of internal variance, motor interference, and a response selection bottleneck.

CognitiveTask

PRP

10.1037/a0015874

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

The source of execution-related dual-task interference: motor bottleneck or response monitoring?

The present study assessed the underlying mechanism of execution-related dual-task interference in the psychological refractory period (PRP) paradigm. The motor bottleneck hypothesis attributes this interference to a processing limitation at the motor level. By contrast, the response monitoring hypothesis attributes it to a bottleneck process that not only selects the appropriate response but also monitors its execution. In two experiments, participants performed ballistic movements of different distances in Task 1 and a choice reaction time task in Task 2. In each experiment, a propagation effect of movement distance on reaction time in Task 2 indicated substantial execution-related interference. To determine the locus of this effect, we manipulated stimulus-response compatibility in Task 2. In line with the motor bottleneck hypothesis, the compatibility effect was partially absorbed during movement execution of Task 1. The results support a motor bottleneck mechanism rather than response monitoring as the source of execution-related dual-task interference.

CognitiveTask

PRP

10.1037/a0015784

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

How strategic is the central bottleneck: can it be overcome by trying harder?

Recent dual-task studies suggest that a bottleneck prevents central mental operations from working on more than one task at a time, especially at relatively low practice levels. It remains highly controversial, however, whether this bottleneck is structural (inherent to human cognitive architecture) or merely a strategic choice. If the strategic hypothesis is testable, it ought to predict that, under sufficiently strong incentives, people could choose to bypass the bottleneck and perform both tasks in parallel. Because the incentives for parallel processing in previous studies have been modest, the authors introduced a novel dual-task paradigm with much greater incentives, induced by strict time deadlines for each task. With this paradigm, bottleneck delays would cause participants to frequently miss the time deadline or make errors, triggering immediate negative consequences (failure feedback). Nevertheless, participants had little success performing central operations in parallel; severe dual-task performance costs were observed, even with relatively easy tasks. These results greatly strengthen the case that the central bottleneck reflects a structural limitation that, at least at modest practice levels, cannot be avoided merely by trying harder.

CognitiveTask

PRP

10.1068/p6313

Perception

Perception

Controlled but independent: effects of mental rotation and developmental dyslexia in dual-task settings.

In two experiments, we compared the performance of normal-reading (n = 26) and dyslexic children (n = 22) in discriminating letters from their mirrored images. In experiment 1, they were always presented in the upright orientation; in experiment 2, they were presented in different angular orientations (0 degrees, 90 degrees, 180 degrees). In order to determine whether task and dyslexia affect reaction times in early or late stages of processing, a dual-task paradigm was adopted in which the primary task was tone discrimination. Stimulus onset asynchrony (SOA) between first and second task was systematically varied (50 ms versus 400 ms). In both experiments dyslexics were slower overall than controls. No effects of mirror-image letters were found. In experiment 2, mental-rotation effects were additive with SOA. In accordance with earlier findings we concluded that the mental-rotation effect involves central processing capacity. Mental-rotation effects were the same for normal-reading and dyslexic children; mental rotation is not impaired in dyslexia. Remarkably, SOA effects were larger in normal readers than in dyslexics. This result was explained by observing that dyslexics experience decision difficulties already on the first task. As a result, they do not benefit optimally from increased latencies between first and second tasks.

CognitiveTask

PRP

10.1037/a0016373

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Attentional requirements for the selection of words from different grammatical categories.

Two grammatical classes are commonly distinguished in psycholinguistic research. The open-class includes content words such as nouns, whereas the closed-class includes function words such as determiners. A standing issue is to identify whether these words are retrieved through similar or distinct selection mechanisms. We report a comparative investigation of the allocation of attentional resources during the retrieval of words from these 2 classes. Previous studies used a psychological-refractory-period paradigm to establish that open-class word retrieval is supported by central attention mechanisms. We applied the same logic to closed-class word retrieval. French native speakers named pictures with determiner noun phrases while they concurrently identified the pitch of an auditory tone. The ease of noun and determiner retrieval was manipulated independently. Results showed that both manipulations affected picture naming and tone discrimination responses in similar ways. This suggests the involvement of central attentional resources in word production, irrespective of word class. These results argue against the commonly held hypothesis that closed-class retrieval is an automatic consequence of syntactic specific processes.

CognitiveTask

PRP

10.1097/FTD.0b013e3181ae4516

Therapeutic drug monitoring

Ther Drug Monit

A liquid chromatography-tandem mass spectrometry method for the determination of 5-Fluorouracil degradation rate by intact peripheral blood mononuclear cells.

5-Fluorouracil (5-FU) is a major chemotherapy drug used for the treatment of tumors. It is catabolized mainly by dihydropyrimidine dehydrogenase, and patients with a complete or partial deficiency of dihydropyrimidine dehydrogenase activity are at risk of developing severe 5-FU-associated toxicity. The aim of this study was to demonstrate that intact peripheral blood mononuclear cells (PBMCs) can be an effective model to evaluate the degradation rate of 5-FU. We developed a sensitive and specific liquid chromatography-tandem mass spectrometry method to measure in vitro the rate of 5-FU degradation by intact PBMC. 5-FU degradation rate was determined by measuring the decrease of a fixed amount of 5-FU (10 microg/mL) added to a solution of PBMC, after 2 hours incubation, expressed as nanogram per milliliter of 5-FU degraded per minute x 10(6) cells. Freshly prepared intact PBMC can degrade efficiently in vitro-added 5-FU. The assay consists of 3 steps: (1) PBMC isolation from peripheral blood, (2) PBMC incubation with 5-FU in vitro for different times, and (3) determination of 5-FU amount to calculate the degradation rate. 5-FU was analyzed by a Q Trap 2000 triple quadrupole/ion trap mass spectrometer in the multiple-reaction-monitoring modes. The chromatographic separation was accomplished using a C18 column with a run time of 16 minutes. By analyzing samples from 39 patients with no 5-FU toxicity, the mean 5-FU degradation rate was 1.85 +/- 0.50 ng x mL(-1) x min(-1) x 10(6) cells. The assessment of a test to measure 5-FU degradation rate in PBMC of patients before 5-FU administration could represent a prescreening method for evaluating the possible toxicity of this drug as an aid to set up a personalized medicine approach for each patient.

CognitiveTask

PRP

10.1037/a0015378

Journal of experimental psychology. General

J Exp Psychol Gen

Parallel response selection disrupts sequence learning under dual-task conditions.

Some studies suggest that dual-task processing impairs sequence learning; others suggest it does not. The reason for this discrepancy remains obscure. It may have to do with the dual-task procedure often used. Many dual-task sequence learning studies pair the serial reaction time (SRT) task with a tone-counting secondary task. The tone-counting task, however, is not ideal for studying the cognitive processes involved in sequence learning. The present experiments sought to identify the nature of the interference responsible for disrupting sequence learning in dual-task situations using more tractable dual-task procedures. Experiments 1 and 2 showed that parallel-interfering central processing disrupts sequence learning. Experiment 3 used a novel combination of the SRT task as the secondary task in a psychological refractory period procedure. It showed that SRT task performance can be disrupted without disrupting sequence learning when that disruption involves a response-selection bottleneck rather than parallel response selection. Together, these results suggest that it is the overlap of central processes involved in successfully performing the 2 tasks concurrently that leads to learning deficits in dual-task sequence learning.

CognitiveTask

PRP

10.1080/17470210902747187

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

When underadditivity of factor effects in the Psychological Refractory Period paradigm implies a bottleneck: evidence from psycholinguistics.

The Psychological Refractory Period (PRP) paradigm is a dual-task procedure that can be used to examine the resource demands of specific cognitive processes. Inferences about the underlying processes are typically based on performance in the second of two speeded tasks. If the effect of a factor manipulated in Task 2 decreases as the stimulus onset asynchrony (SOA) between tasks decreases (underadditivity), the normative inference is that the effect of this factor occurs prior to a limited-capacity central processing mechanism. In contrast, if the effect of a factor is additive with SOA then the inference is that this indexes a process that either uses a limited-capacity central processing mechanism or occurs after some process that uses this mechanism. A heretofore unidentified exception to this logic arises when Task 2 involves two separate processes that operate in parallel, but compete. Interference with one process in Task 2 because of work on Task 1 will eliminate or reduce competition within Task 2 and is hence manifest as an underadditive interaction with decreasing SOA. This is illustrated here by reference to a PRP experiment in which the ubiquitous effect of spelling-to-sound regularity on reading aloud time is eliminated at a short SOA and by consideration of three converging lines of investigation in the PRP paradigm when Task 2 involves reading aloud.

CognitiveTask

PRP

10.1037/a0013029

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Operation compatibility: a neglected contribution to dual-task costs.

Traditionally, dual-task interference has been attributed to the consequences of task load exceeding capacity limitations. However, the current study demonstrates that in addition to task load, the mutual compatibility of the concurrent processes modulates whether 2 tasks can be performed in parallel. In 2 psychological refractory period experiments, task load and process compatibility were independently varied. In Experiment 1, participants performed 2 mental rotation tasks. Task load (rotation angle) and between-task compatibility in rotation direction were varied. Results suggest more considerable parallel execution of compatible than of incompatible operations, arguing for the need to attribute dual-task interference not only to structural but also to functional capacity limitations. Experiment 2 tested whether functional capacity limitations to dual-task performance can be caused only by demanding processes or whether they are also induced by relatively automatic processes. Results indicate that an irrelevant circular movement of Stimulus 2 interfered more with mental rotation of Stimulus 1 if the rotation directions were opposite than if they were equal. In conclusion, compatibility of concurrent processes constitutes an indispensable element in explaining dual-task performance.

CognitiveTask

PRP

10.3758/PBR.16.2.282

Psychonomic bulletin & review

Psychon Bull Rev

Nonautomatic emotion perception in a dual-task situation.

Are emotions perceived automatically? Two psychological refractory period experiments were conducted to ascertain whether emotion perception requires central attentional resources. Task 1 required an auditory discrimination (tone vs. noise), whereas Task 2 required a discrimination between happy and angry faces. The difficulty of Task 2 was manipulated by varying the degree of emotional expression. The stimulus onset asynchrony (SOA) between Task 1 and Task 2 was also varied. Experiment 1 revealed additive effects of SOA and Task 2 emotion-perception difficulty. Experiment 2 replicated the additive relationship with a stronger manipulation of emotion-perception difficulty. According to locus-of-slack logic, our participants did not process emotional expressions while central resources were devoted to Task 1. We conclude that emotion perception is not fully automatic.

CognitiveTask

PRP

10.1016/j.cogpsych.2006.08.003

Cognitive psychology

Cogn Psychol

On the optimality of serial and parallel processing in the psychological refractory period paradigm: effects of the distribution of stimulus onset asynchronies.

Within the context of the psychological refractory period (PRP) paradigm, we developed a general theoretical framework for deciding when it is more efficient to process two tasks in serial and when it is more efficient to process them in parallel. This analysis suggests that a serial mode is more efficient than a parallel mode under a wide variety of conditions and thereby suggests that ubiquitous evidence of serial processing in PRP tasks could result from performance optimization rather than from a structural bottleneck. The analysis further suggests that the experimenter-selected distribution of stimulus onset asynchronies (SOAs) influences the relative efficiency of the serial and parallel modes, with a preponderance of short SOAs favoring a parallel mode. Experiments varying the distribution of SOAs were conducted, and the results suggest that there is a shift from a more serial mode to a more parallel mode as the likelihood of short SOAs increases.

CognitiveTask

PRP

10.1080/17470210802570994

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Is advance reconfiguration in voluntary task switching affected by the design employed?

In task switching, when the amount of preparation time is increased, a reduction in switch cost or RISC effect is observed. This RISC effect is frequently attributed to advance reconfiguration processes. In the explicit task-cueing procedure, RISC effects are observed when varying the preparation time within participants but not when varying the preparation time across participants--a finding suggesting that RISC effects in the explicit task-cueing procedure are restricted to specific designs. The present study investigated RISC effects in voluntary task switching and compared RISC effects in a within-subjects design with RISC effects in a between-subjects design. Our results indicate that RISC effects are present in both designs. We conclude that advance reconfiguration in voluntary task switching is robust.

CognitiveTask

PRP

10.1080/17470210701536856

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Motor limitation in dual-task processing with different effectors.

According to the extended bottleneck model, dual-task interference does not arise only from a central bottleneck but also from processing limitations at the motor stage. Evidence for this assumption has previously been found only for same-effector tasks but not for different-effector tasks. In order to examine the existence of motor interference with different effectors, we used the psychological refractory period paradigm and employed response sequences of different length in Task 1 (R1 sequence length). Experiment 1 incorporated vocal response sequences in Task 1 and a manual response in Task 2. In Experiment 2, the assignment of the effectors to the two tasks was reversed. In both experiments, the long R1 sequence prolonged reaction time for Task 2 (RT2), and this effect was reduced with decreasing temporal overlap of the two tasks. Thus, the present experiments demonstrate motor interference between different-effector tasks. This interference may be due to on-line programming or to central response monitoring.

CognitiveTask

PRP

10.1111/j.1467-9280.2008.02211.x

Psychological science

Psychol Sci

Limits on introspection: distorted subjective time during the dual-task bottleneck.

Which cognitive processes are accessible to conscious report? To study the limits of conscious reportability, we designed a novel method of quantified introspection, in which subjects were asked, after each trial of a standard cognitive task, to estimate the time spent completing the task. We then applied classical mental-chronometry techniques, such as the additive-factors method, to analyze these introspective estimates of response time. We demonstrate that introspective response time can be a sensitive measure, tightly correlated with objective response time in a single-task context. In a psychological-refractory-period task, however, the objective processing delay resulting from interference by a second concurrent task is totally absent from introspective estimates. These results suggest that introspective estimates of time spent on a task tightly correlate with the period of availability of central processing resources.

CognitiveTask

PRP

10.1080/13554790802498955

Neurocase

Neurocase

The Influence of refractoriness upon comprehension of non-verbal auditory stimuli.

An investigation of non-verbal auditory comprehension in two patients with global aphasia following stroke is reported. The primary aim of the investigation was to establish whether refractory access disorders can affect non-verbal input modalities. All previous reports of refractoriness, a cognitive syndrome characterized by response inconsistency, sensitivity to temporal factors and insensitivity to item frequency, have involved comprehension tasks which have a verbal component. Two main experiments are described. The first consists of a novel sound-to-picture and sound-to-word matching task in which comprehension of environmental sounds is probed under conditions of semantic relatedness and semantic unrelatedness. In addition to the two stroke patients, the performance of a group of 10 control patients with non-vascular pathology is reported, along with evidence of semantic relatedness effects in sound comprehension. The second experiment examines environmental sound comprehension within a repetitive probing paradigm which affords assessment of the effects of semantic relatedness, response consistency and presentation rate. It is demonstrated that the two stroke patients show a significant increase in error rate across multiple probes of the same set of sound stimuli, indicating the presence of refractoriness within this non-verbal domain. The implications of the results are discussed with reference to our current understanding of the mechanisms of refractoriness.

CognitiveTask

PRP

10.1016/j.biopsycho.2008.10.001

Biological psychology

Biol Psychol

Contingent capture of visual-spatial attention depends on capacity-limited central mechanisms: evidence from human electrophysiology and the psychological refractory period.

It has recently been demonstrated that a lateralized distractor that matches the individual's top-down control settings elicits an N2pc wave, an electrophysiological index of the focus of visual-spatial attention, indicating that contingent capture has a visual-spatial locus. Here, we investigated whether contingent capture required capacity-limited central resources by incorporating a contingent capture task as the second task of a psychological refractory period (PRP) dual-task paradigm. The N2pc was used to monitor where observers were attending while they performed concurrent central processing known to cause the PRP effect. The N2pc elicited by the lateralized distractor that matched the top-down control settings was attenuated in high concurrent central load conditions, indicating that although involuntary, the deployment of visual-spatial attention occurring during contingent capture depends on capacity-limited central resources.

CognitiveTask

PRP

10.1016/j.cub.2008.08.039

Current biology : CB

Curr Biol

Cognitive neuroscience: searching for the bottleneck in the brain.

People simply cannot do two things at once, as shown by research on the so-called psychological refractory period. A new neuroimaging study has now localized the response-selection bottleneck underlying the psychological refractory period to a frontoparietal network.

CognitiveTask

PRP

10.1037/a0013123

Psychological review

Psychol Rev

Queuing network modeling of the psychological refractory period (PRP).

The psychological refractory period (PRP) is a basic but important form of dual-task information processing. Existing serial or parallel processing models of PRP have successfully accounted for a variety of PRP phenomena; however, each also encounters at least 1 experimental counterexample to its predictions or modeling mechanisms. This article describes a queuing network-based mathematical model of PRP that is able to model various experimental findings in PRP with closed-form equations including all of the major counterexamples encountered by the existing models with fewer or equal numbers of free parameters. This modeling work also offers an alternative theoretical account for PRP and demonstrates the importance of the theoretical concepts of "queuing" and "hybrid cognitive networks" in understanding cognitive architecture and multitask performance.

CognitiveTask

PRP

10.3758/MC.36.7.1262

Memory & cognition

Mem Cognit

Bypassing the central bottleneck after single-task practice in the psychological refractory period paradigm: evidence for task automatization and greedy resource recruitment.

In this research, the controversial issue of whether the central bottleneck can be bypassed through task automatization was investigated. To examine this issue, participants received six single-task practice sessions with an auditory-vocal task (low vs. high pitch). We then assessed dual-task performance using the analytically tractable psychological refractory period (PRP) paradigm, in which the highly practiced auditory-vocal task was presented as Task 2, along with an unpracticed visual-manual Task 1. The results provide evidence of bottleneck bypass for virtually all the participants (17 out of 20). Several converging tests suggest that the bottleneck reemerged, however, in a follow-up experiment with tasks presented in the opposite order (auditory-vocal Task 1 and visual-manual Task 2). One possible explanation is that tasks greedily recruit central resources when available, even though they can operate without central resources when unavailable.

CognitiveTask

PRP

10.1016/j.actpsy.2008.09.001

Acta psychologica

Acta Psychol (Amst)

Are spatial responses to visuospatial stimuli and spoken responses to auditory letters ideomotor-compatible tasks? Examination of set-size effects on dual-task interference.

Previous studies have paired a visual-manual Task 1 with an auditory-vocal Task 2 to evaluate whether the psychological refractory period (PRP) effect is eliminated with two ideomotor-compatible tasks (for which stimuli resemble the response feedback). The present study varied the number of stimulus-response alternatives for Task 1 in three experiments to determine whether set-size and PRP effects were absent, as would be expected if the tasks bypass limited-capacity response-selection processes. In Experiments 1 and 2, the visual-manual task was used as Task 1, with lever-movement and keypress responses, respectively. In Experiment 3, the auditory-vocal task was used as Task 1 and the visual-manual task as Task 2. A significant lengthening of reaction time for 4 vs. 2 alternatives was found for the visual-manual Task 1 and the Task 2 PRP effect in Experiments 1 and 2, suggesting that the visual-manual task is not ideomotor compatible. Neither effect of set size was significant for the auditory-vocal Task 1 in Experiment 3, but there was still a Task 2 PRP effect. Our results imply that neither version of the visual-manual task is ideomotor compatible; other considerations suggest that the auditory-vocal task may also still require response selection.

CognitiveTask

PRP

10.1371/journal.pone.0003196

PloS one

PLoS One

Delays without mistakes: response time and error distributions in dual-task.

When two tasks are presented within a short interval, a delay in the execution of the second task has been systematically observed. Psychological theorizing has argued that while sensory and motor operations can proceed in parallel, the coordination between these modules establishes a processing bottleneck. This model predicts that the timing but not the characteristics (duration, precision, variability...) of each processing stage are affected by interference. Thus, a critical test to this hypothesis is to explore whether the quality of the decision is unaffected by a concurrent task. In number comparison--as in most decision comparison tasks with a scalar measure of the evidence--the extent to which two stimuli can be discriminated is determined by their ratio, referred as the Weber fraction. We investigated performance in a rapid succession of two non-symbolic comparison tasks (number comparison and tone discrimination) in which error rates in both tasks could be manipulated parametrically from chance to almost perfect. We observed that dual-task interference has a massive effect on RT but does not affect the error rates, or the distribution of errors as a function of the evidence. Our results imply that while the decision process itself is delayed during multiple task execution, its workings are unaffected by task interference, providing strong evidence in favor of a sequential model of task execution.

CognitiveTask

PRP

10.1080/17470210701643397

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Effects of stimulus features and instruction on response coding, selection, and inhibition: evidence from repetition effects under task switching.

The coding of stimuli and responses is crucial for human behaviour. Here, we focused primarily on the response codes (or response categories). As a method, we applied a combined dual-task and task-switch paradigm with a fixed task-to-hand mapping. Usually, negative effects (i.e., costs) are observed for response category repetitions under task switching. However, in several previous studies it has been proposed that such repetition effects do not occur, if the stimulus categories (e.g., "odd" if digits have to be classified according to their parity feature) are unequivocally mapped to specific responses. Our aim was to test this hypothesis. In the present experiments, we were able to distinguish between three different types of possible response codes. The results show that the participants generally code their responses according to abstract response features (left/right, or index/middle finger). Moreover, the spatial codes were preferred over the finger-type codes even if the instructions stressed the latter. This preference, though, seemed to result from a stimulus-response feature overlap, so that the spatial response categories were primed by the respective stimulus features. If there was no such overlap, the instructions determined which type of response code was involved in response selection and inhibition.

CognitiveTask

PRP

10.1055/s-0028-1082882

Seminars in speech and language

Semin Speech Lang

Models of attention and dual-task performance as explanatory constructs in aphasia.

Aphasia has traditionally been viewed as a loss or impairment of language. However, evidence is presented suggesting that language mechanisms are fundamentally preserved and that aphasic language behaviors are instead due to impairments of cognitive processes supporting their construction. These processes may be understood as a linguistically specialized attentional system that is vulnerable to competition from other processing domains. We present two models of attention that focus on competition for central processing and discuss findings from dual-task studies of normal and aphasic performance. First, competing language and nonlanguage tasks appear to share limited-capacity, parallel processing resources. Second, aphasic individuals demonstrate slowed central processing that could be due to a reduction in processing capacity or ability to allocate that capacity. Third, the attention models discussed bear a coherent relationship to current models of language processing. Clinical implications of a cognitive processing account of aphasia are also considered.

CognitiveTask

PRP

10.1523/JNEUROSCI.0948-08.2008

The Journal of neuroscience : the official journal of the Society for Neuroscience

J Neurosci

Brain mechanisms of serial and parallel processing during dual-task performance.

The psychological refractory period (PRP) refers to the fact that humans typically cannot perform two tasks at once. Behavioral experiments have led to the proposal that, in fact, peripheral perceptual and motor stages continue to operate in parallel, and that only a central decision stage imposes a serial bottleneck. We tested this model using neuroimaging methods combined with innovative time-sensitive analysis tools. Subjects performed a dual-task visual-auditory paradigm in which a delay of 300 ms was injected into the auditory task either within or outside of the dual-task interference period. Event-related potentials indicated that the first approximately 250 ms of processing were insensitive to dual-task interference, and that the PRP was mainly reflected in a delayed global component. By a clustering analysis based on time-resolved functional magnetic resonance imaging, we identified networks with qualitatively different timing properties: sensory areas tracked the objective time of stimulus presentation, a bilateral parietoprefrontal network correlated with the PRP delay, and an extended bilateral network that included bilateral posterior parietal cortex, premotor cortex, supplementary motor area, anterior part of the insula, and cerebellum was shared by both tasks during the extent of dual-task performance. The results provide physiological evidence for the coexistence of serial and parallel processes within a cognitive task.

CognitiveTask

PRP

10.1027/1618-3169.55.3.203

Experimental psychology

Exp Psychol

Valence processing bypassing the response selection bottleneck? Evidence from the psychological refractory period paradigm.

The activation of semantic categories has often been claimed to occur in an attention-free, unconditionally automatic fashion (e.g., Bargh & Chartrand, 1999; Ferguson & Bargh, 2004). Using a dual-task procedure we tested whether the activation of valence categories is restricted by dual-task specific attentional limitations. For this reason we implemented a modified Eriksen-flanker task as Task 2 in a psychological refractory period paradigm. Participants were to judge the frequency of a tone in Task 1 and the valence of a target word in the presence of irrelevant flanker words in Task 2. Two different flanker categories ensured the activation of semantic categories instead of S-R based response activation. The most important result was an underadditive interaction between flanker congruency and the amount of temporal overlap between tasks that was independent of flanker type. Following the locus-of-slack logic, we interpret these findings as evidence for Task 2 processing parallel to bottleneck-stage processing in Task 1. This extends previous findings by showing that not only number categories (Fischer, Schubert, & Miller, 2007; Oriet, Tombu, & Jolicouer, 2005), but also semantic valence categories can be activated despite dual-task capacity limitations.

CognitiveTask

PRP

10.1037/0096-3445.137.2.282

Journal of experimental psychology. General

J Exp Psychol Gen

The nature of phoneme representation in spoken word recognition.

Four experiments used the psychological refractory period logic to examine whether integration of multiple sources of phonemic information has a decisional locus. All experiments made use of a dual-task paradigm in which participants made forced-choice color categorization (Task 1) and phoneme categorization (Task 2) decisions at varying stimulus onset asynchronies. In Experiment 1, Task 2 difficulty was manipulated using words containing matching or mismatching coarticulatory cues to the final consonant. The results showed that difficulty and onset asynchrony combined in an underadditive way, suggesting that the phonemic mismatch was resolved prior to a central decisional bottleneck. Similar results were found in Experiment 2 using nonwords. In Experiment 3, the manipulation of task difficulty involved lexical status, which once again revealed an underadditive pattern of response times. Finally, Experiment 4 compared this prebottleneck variable with a decisional variable: response key bias. The latter showed an additive pattern of responses. The experiments show that resolution of phonemic ambiguity can take advantage of cognitive slack time at short asynchronies, indicating that phonemic integration takes place at a relatively early stage of spoken word recognition.

CognitiveTask

PRP

10.1007/s00426-008-0152-8

Psychological research

Psychol Res

The role of crosstalk in dual-task performance: evidence from manipulating response-code overlap.

The present study examined the role of crosstalk in dual-task interference using a combination of a nonspeeded visual task and an auditory-manual reaction time (RT) task. The potential for dual-task crosstalk was introduced by presenting in the visual task objects (e.g., a cup with a handle), which "afford" associated responses that were either spatially compatible or incompatible with the response in the RT task. Crucially, the degree of crosstalk was varied by instructing participants either to attend to the left-right orientation of the objects, creating explicit cross-task response-code overlap ("strong crosstalk"), or to attend to object identity (no direct overlap; "weak crosstalk"). The data indicated a relative benefit for cross-task compatible trials, which was much greater with strong crosstalk than with weak crosstalk. Crucially, however, even on compatible trials dual-task performance was substantially worse with strong crosstalk than with weak crosstalk. This overall cost of crosstalk suggests interference of response codes even on compatible dual-task trials.

CognitiveTask

PRP

10.1037/0096-1523.34.2.398

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Viewer perspective affects central bottleneck requirements in spatial translation tasks.

A psychological refractory period (PRP) approach and the locus of slack logic were applied to examine the novel question of whether spatial translation processes can begin before the central bottleneck when effector or noneffector stimuli are processed from an egocentric (viewer-centered) perspective. In single tasks, trials requiring spatial translations were considerably slower than trials without translations (Experiment 1). Dual tasks consisted of tone discriminations (Task 1) and spatial translations (Task 2) using PRP methods with different manipulations on perceptual and response demands. When a viewer-centered perspective was used, the effect of spatial translation was reduced at short compared with long stimulus onset asynchronies (SOAs) when the potential for code overlap between tasks was removed (Experiments 2, 3, and 4); this finding supports the view that translation processes can begin before the central bottleneck. When an allocentric (non-viewer-centered) perspective was used (Experiment 5), the slowing associated with spatial translation was additive with SOA, suggesting that the processes of spatial translation cannot begin before the bottleneck. These findings highlight the importance of viewer perspective on central bottleneck requirements. Findings are further discussed in relation to the dorsal-ventral model of action and perception.

CognitiveTask

PRP

10.1037/0096-1523.34.2.376

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Response activation in overlapping tasks and the response-selection bottleneck.

The authors investigated the impact of response activation on dual-task performance by presenting a subliminal prime before the stimulus in Task 2 (S2) of a psychological refractory period (PRP) task. Congruence between prime and S2 modulated the reaction times in Task 2 at short stimulus onset asynchrony despite a PRP effect. This Task 2 congruence effect was paralleled by a Task 1 congruence effect and emerged exclusively under conditions of cross talk, whereas it did not occur under dual-task conditions preventing cross talk between tasks. This suggests that response activation operates during the PRP in dual tasks and affects the response times in Task 2 via cross talk between common processing elements at prebottleneck stages but not by directly affecting the postbottleneck stages.

CognitiveTask

PRP

10.1037/0278-7393.34.2.422

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Reading aloud: spelling-sound translation uses central attention.

Contrary to the received view that reading aloud reflects processes that are "automatic," recent evidence suggests that some of these processes require a form of attention. This issue was investigated further by examining the effect of a prior presentation of exception words (words whose spelling-sound translation are atypical, such as pint as compared with mint, hint, or lint) and pseudohomophones (nonwords that sound identical to words, such as brane from brain) on reading aloud in the context of the psychological refractory period paradigm. For exception words, the joint effects of repetition and stimulus onset asynchrony (SOA) yielded an underadditive interaction on the time to read aloud, replicating previous work -- a short SOA between Task 1 and Task 2 increased reaction time (RT) and reduced the magnitude of the repetition effect relative to the long SOA. For pseudohomophones, in contrast, the joint effects of repetition and SOA were additive on RT. These results provide converging evidence for the conclusion that (a) processing up to and including the orthographic input lexicon does not require central attention when reading aloud, whereas (b) translating lexical and sublexical spelling to sound requires the use of central attention.

CognitiveTask

PRP

10.1037/0278-7393.34.2.282

Journal of experimental psychology. Learning, memory, and cognition

J Exp Psychol Learn Mem Cogn

Age of acquisition and word frequency effects in picture naming: a dual-task investigation.

In 2 experiments, the authors explored age of acquisition (AoA) and word frequency (WF) effects in picture naming using the psychological refractory period paradigm. In Experiment 1, participants named a picture and then, a short time later, categorized 1 of 3 possible auditory tones as high, medium, or low. Both AoA (Experiment 1A) and WF (Experiment 1B) effects propagated onto tone discrimination reaction times (RTs), with the effects of AoA being stronger. In Experiment 2, the to-be-named picture followed the auditory tone by a varying interval. As the interval decreased, picture naming RTs increased. The relationship between the interval and AoA (Experiment 2A) was reliably underadditive; AoA effects were eliminated at the shortest interval. In contrast, WF (Experiment 2B) was additive with the effects of the interval. These results demonstrate an empirical dissociation between AoA and WF effects. AoA affects processing stages that precede those that are sensitive to WF. The implications for theories of picture naming are discussed.

CognitiveTask

PRP

10.1016/j.cogpsych.2007.06.004

Cognitive psychology

Cogn Psychol

Response grouping in the psychological refractory period (PRP) paradigm: models and contamination effects.

Response grouping is a ubiquitous phenomenon in psychological refractory period (PRP) tasks, yet it hampers the analysis of dual-task performance. To account for response grouping, we developed several extended versions of the standard bottleneck model, each of which incorporates a possible grouping mechanism into this model. Computer simulations were used to assess how the predictions of the standard model would change with each grouping mechanism. One set of simulations investigated the basic effects of grouping on the means and intercorrelation of the reaction times in the two tasks, as well as the percentage of trials with short interresponse times (IRTs). A second set of simulations examined whether response grouping would invalidate the use of PRP paradigms for localizing experimental effects. Finally, we investigated whether the post-hoc elimination of trials with short IRTs removes the contaminating effects of response grouping.

CognitiveTask

PRP

10.1027/1618-3169.55.5.313

Experimental psychology

Exp Psychol

Does the central bottleneck encompass voluntary selection of hedonically based choices?

A large literature on multitasking bottlenecks suggests that people cannot generally make decisions or select responses in two different tasks at the same time. However, these tasks have all involved retrieving preinstructed responses, rather than spontaneously choosing actions based on anticipated hedonic consequences. To assess whether the same bottlenecks encompasses voluntary choices, a gambling decision was utilized as the second of two tasks in a psychological refractory period (PRP) design. Three decision-related factors were identified that affected latency of responding in the gambling task. All proved to be additive with stimulus-onset asynchrony (SOA) in dual-task blocks. The results indicate that making a choice to try to optimize outcomes is subject to the same processing bottleneck as the retrieval of preinstructed responses that has been the mainstay of attention and performance research.

CognitiveTask

PRP

10.3758/bf03193502

Memory & cognition

Mem Cognit

Evidence for parallel semantic memory retrieval in dual tasks.

In this dual-task study, we applied both cross-talk logic and locus-of-slack logic to test whether participants can retrieve semantic categories in Task 2 in parallel to Task 1 bottleneck processing. Whereas cross-talk logic can detect parallel memory retrieval only in conditions of categorical overlap between tasks, the locus-of-slack approach is independent of such restrictions. As was expected, using the cross-talk logic, we found clear evidence for parallel retrieval of semantic categories when there was categorical overlap between tasks (Experiment 1). Locus-of-slack-based evidence for parallel semantic retrieval was found, however, both in conditions with (Experiment 1) and in those without (Experiment 2) categorical overlap between tasks. Crucially,however, increasing the demand for resources required to switch from Task 1 to Task 2 eliminated even the locus-of-slack-based evidence for parallel memory retrieval during the psychological refractory period (Experiment 3). Together, our results suggest that parallel retrieval is not bound to conditions of categorical overlap between tasks but, instead, is contingent upon resources needed for switching between tasks (e.g., Oriet, Tombu, & Jolicoeur, 2005).

CognitiveTask

PRP

10.1162/jocn.2008.20030

Journal of cognitive neuroscience

J Cogn Neurosci

Parallel response selection after callosotomy.

Two studies [Ivry, R. B., Franz, E. A., Kingstone, A., & Johnston, J. C. The psychological refractory period effect following callosotomy: Uncoupling of lateralized response codes. Journal of Experimental Psychology: Human Perception and Performance, 24, 463-480, 1998; Pashler, H., Luck, S., Hillyard, S. A., Mangun, G. R., O'Brien, S., & Gazzaniga, M. S. Sequential operation of disconnected hemispheres in split-brain patients. NeuroReport, 5, 2381-2384, 1994] reported robust dual-task costs in split-brain patients even when the two tasks were associated with separate cerebral hemispheres. Although the patients failed to demonstrate specific forms of interference observed in control participants, the timing of the two responses suggested that performance was constrained such that the responses could not be initiated independently. Alternatively, the split-brain participants may have adopted a strategy in which the second response was withheld until the first was initiated. The present study revisits this phenomenon using a procedure in which the stimuli for both tasks are presented simultaneously and neither is given priority over the other. Under these conditions, neurologically intact participants show robust dual-task costs that are mediated by compatibility effects between the responses of the two hands. In contrast, the split-brain participants show greatly reduced dual-task costs and compatibility effects. The minimal dual-task costs observed in the current study indicate that previous dual-task costs in split-brain patients may be strategic, reflecting experimental instructions to prioritize one task, rather than reflect fundamental constraints of the cognitive architecture.

CognitiveTask

PRP

10.3758/bf03196827

Psychonomic bulletin & review

Psychon Bull Rev

The picture-word interference effect is not a Stroop effect.

A psychological refractory period (PRP) paradigm was used to isolate the locus of the picture-word interference effect along the chain of processes subtended in name production. Two stimuli were presented sequentially on each trial, separated by a varying stimulus onset asynchrony (SOA). The first stimulus, SI, was a tone that required a manual response. The second stimulus, S2, was a picture-word stimulus associated with picture naming. The distractor word was conceptually related to the picture on half of the trials, and unrelated in the other trials. A picture-word interference effect was found at long SOA, but not at short SOA. Such underadditive interaction between SOA and semantic relatedness suggests strongly that the locus of the picture-word interference effect is functionally earlier than the PRP effect locus. The results are discussed in relation to models of word production suggesting the involvement of central mechanisms in the selection of lexical output.

CognitiveTask

PRP

10.1080/13803390701399278

Journal of clinical and experimental neuropsychology

J Clin Exp Neuropsychol

Procedural learning eliminates specific slowing down of response selection in patients with idiopathic Parkinson syndrome.

Patients with idiopathic Parkinson syndrome and normally aged controls participated in a psychological refractory period experiment. Two tasks were presented on each trial: auditory discrimination of high versus low tones, followed by visual classification of letters versus their mirror images. Speeded responses to both tasks were required. Stimulus onset asynchrony between the tasks was varied (short vs. long). Both groups showed equal response times overall, but patients were slower on the second task in the short stimulus onset asynchrony condition. This effect was eliminated with practice. The results were interpreted in terms of reduced capacity for cognitive processes involving decision making as a secondary symptom of the Parkinson syndrome.

CognitiveTask

PRP

10.1590/s1516-44462006005000058

Revista brasileira de psiquiatria (Sao Paulo, Brazil : 1999)

Braz J Psychiatry

[Treatment-resistant mood disorders].

Mood disorders are the most prevalent psychiatric disorders. Despite new insights and advances on the neurobiological basis and therapeutic approaches for bipolar disorders and recurrent depression, elevated prevalence of recurrence, persistent sub-syndromal symptoms and treatment resistance are challenging aspects and need to be urgently addressed. The objective of this literature review is to evaluate the current concepts of treatment resistance and refractoriness in mood disorders. Genetic factors, misdiagnosis, use of inappropriate pharmacological approaches, non-compliance and biological/psychosocial stressors account for dysfunctions in mood regulation, thus increasing the prevalence of refractory mood disorders. Regarding available treatments, the use of effective doses during an adequate period followed by augmentation with a second and/or third agent, and finally switching to other agent are steps frequently necessary to optimize efficacy. However, in the treatment-resistant paradigm, drugs mimicking standard strategies, which target preferentially the monoaminergic system, can present reduced therapeutic effects. Thus, the search for new effective treatments for mood disorders is critical to decreasing the overall morbidity secondary to treatment resistance. Emerging strategies targeting brain plasticity pathways or 'plasticity enhancers', including antiglutamatergic drugs, glucocorticoid receptor antagonists and neuropeptides, have been considered promising therapeutic options for difficult-to-treat mood disorders.

CognitiveTask

PRP

10.1037/cjep2007011

Canadian journal of experimental psychology = Revue canadienne de psychologie experimentale

Can J Exp Psychol

Data-limited manipulations of T1 difficulty modulate the attentional blink.

When two targets are embedded in a temporal stream of distractors, second-target identification is initially impaired and then gradually improves as intertarget interval lengthens (attentional blink; AB). According to bottleneck models of the AB, difficulty of first-target processing should modulate the magnitude of the second-target deficit. To test this, we examined whether a data-limited manipulation of T1 difficulty (forward masking) would modulate AB magnitude. In two experiments, we show that data-limited manipulations of T1 difficulty do affect the AB, so long as T1 is not masked by an immediately trailing distractor. When such a trailing item is present, the relationship between T1 difficulty and the AB disappears.

CognitiveTask

PRP

10.1016/j.neuropsychologia.2007.05.022

Neuropsychologia

Neuropsychologia

Cross-modal multitasking processing deficits prior to the central bottleneck revealed by event-related potentials.

We investigated whether concurrent processing of a tone (T1) interferes with early sensory-perceptual processing of a visual target (T2) in variants of the psychological refractory period paradigm using the event-related potential (ERP) method and 70-channel electroencephalographic recordings. T1, which required a speeded response, was presented in all trials. In half of the trials, T1 was followed by a bilateral visual display, T2, which also required a speeded response. A single T1-T2 stimulus onset asynchrony was adjusted dynamically to maximize task overlap in a hard-Task1 condition while minimizing task overlap in an easy-Task1 condition. The ERP to T1 in trials with only T1 presented (uncontaminated by T2) enabled us to subtract T1-related activity from the dual-task T2-locked ERPs. An attenuation of the T2-locked occipital N1 was observed in the hard-Task1 condition, relative to the easy-Task1 condition, both when T2 required a discriminative response and a detection response. An attenuation of the visual P1 component was also observed when T2 required a discriminative response. The N2pc was also attenuated, and the sustained posterior contralateral negativity (SPCN) was delayed, by concurrent processing in the discrimination task. Implications for models of dual-task interference are discussed.

CognitiveTask

PRP

10.1007/s00221-007-1028-7

Experimental brain research

Exp Brain Res

The impact of Degraded distractors on (Nondegraded) target identification.

In this series of experiments, based on Biederman's Recognition by Components theory, we postulate that corners (vertices) of objects are crucial in programming and execution of goal-directed action. We used a distractor interference paradigm to present line drawings of letters (M and W) with distractors (also M and W), which were either nondegraded or degraded (that is, corners or line segments missing). Degraded distractors caused less interference overall (reduced response times and errors) than Nondegraded distractors, when these were presented peripherally or at fixation (Experiments 1 and 2). When presented at fixation, however, distractors with corners missing caused greater interference than distractors with line segments missing. This pattern was not replicated with non-identical, non-mirror reversed stimuli (H and E: Experiment 3). We speculate that corners are critical in determining the extent of distractor interference. When missing from view, and given sufficient attentional resources and structural similarity, they may be reconstructed by the visuomotor system to aid performance to the target.

CognitiveTask

PRP

10.1016/j.biopsycho.2007.05.003

Biological psychology

Biol Psychol

Semantic and repetition priming within the attentional blink: an event-related brain potential (ERP) investigation study.

An attentional blink (AB) paradigm was used to directly compare semantic and repetition priming for reported words versus missed words. Three target words (T1, T2, T3) were embedded in a rapidly presented stream of non-word distractors for report at the end of each trial. Whereas T1 was not related to either T2 or T3, T2 and T3 could be unrelated words, semantically related words, or identical. Semantic and repetition priming effects were evident in both behavioral and electrophysiological measures on T3, whether T2 was accurately reported or 'blinked'. These results suggest that semantic and repetition priming effects, under rapid serial visual presentation conditions, are modulated by at least partially overlapping neural mechanisms.

CognitiveTask

PRP

10.1111/j.1467-9280.2007.01921.x

Psychological science

Psychol Sci

Central slowing during the night.

The present study determined whether central information processing is subject to a circadian rhythm and, therefore, contributes to the well-known time-of-day effect on reaction time (RT). To assess the duration of central processing chronometrically, we employed the psychological refractory period (PRP) paradigm. In this task, subjects make fast responses to two successive stimuli. RT to the second stimulus is usually prolonged as the interval between the two stimuli decreases. This PRP effect is commonly attributed to a central-processing bottleneck. Subjects performed the PRP task every 2 hr during 28 hr of constant wakefulness under controlled conditions. The PRP effect was most pronounced in the early morning. We conclude that central processing is subject to a circadian rhythm, exhibiting a slowing during the night and a nadir in the early morning.

CognitiveTask

PRP

10.1037/0096-1523.33.3.627

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Action-effect codes in and before the central bottleneck: evidence from the psychological refractory period paradigm.

Voluntary motor actions aim at and are thus governed by predictable action effects. Therefore, representations of an action's effects normally must become activated prior to the action itself. In 5 psychological refractory period experiments the authors investigated whether the activation of such effect representations coincides with the response selection stage of information-processing theories. Participants performed 2 choice reaction tasks, separated by variable stimulus onset asynchronies. The authors varied the compatibility between responses and forthcoming sensorial effects (Experiments 1, 2, 3, and 5) or between responses and effect-resembling stimuli (Experiments 4 and 5) in one of the tasks. They observed that compatibility influences from forthcoming (anticipated) response effects were located within the response selection bottleneck, whereas compatibility influences from action-preceding (perceived) effects were due to processes before the bottleneck. These results point to a crucial role of the endogenous activation of action-effect representations for the selection of voluntary motor responses.

CognitiveTask

PRP

10.1037/0096-1523.33.3.610

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Decomposing sources of response slowing in the PRP paradigm.

The mechanism underlying the reaction time (RT2) slowing to the 2nd of 2 successively presented stimuli (S1 and S2) in the psychological refractory period paradigm was investigated. Stimulus onset synchrony (SOA) between S1 and S2, contrast of S2, and Task 2 set-level compatibility was manipulated. Specifically, the authors used a psychophysiological approach to examine RT2 slowing in trials in which the reaction time to S1 (RT1) was shorter than the SOA. For trials with RT1 < SOA, the clear decrease in RT2 with increasing SOA was underadditive with the S2 contrast effect, but additive with compatibility. Electrophysiological measures revealed an exclusively premotoric locus of RT2 slowing. These findings indicate that a central bottleneck stage is occupied for some period after response to S1 execution, consistent with an extended response selection bottleneck account.

CognitiveTask

PRP

10.3758/bf03194039

Psychonomic bulletin & review

Psychon Bull Rev

Electrophysiological evidence of central interference in the control of visuospatial attention.

Visuospatial attention can be deployed to different locations in space without movement of the eyes. A large body of human electrophysiological studies reveals enhanced sensory-perceptual responses to stimuli that appear at an attended location. However, it is not clear that the mechanisms that underlie visuospatial attention are under the control of attention mechanisms that limit central processing in multiple-task situations. We investigated this question by incorporating a visual task that required the deployment of visuospatial attention as the second task of psychological refractory period (PRP) dual-task paradigms. The N2pc component of the event-related potential was used as an electrophysiological index of the moment-by-moment deployment of visuospatial attention to monitor when and where observers were attending while they performed concurrent central processing known to cause the PRP effect. Electrophysiological evidence shows that central processing interfered with the N2pc, suggesting that visuospatial attention is under the control of capacity-limited central mechanisms.

CognitiveTask

PRP

10.3758/bf03194025

Psychonomic bulletin & review

Psychon Bull Rev

Effects of redundant auditory stimuli on reaction time.

Auditory redundancy gains were assessed in two experiments in which a simple reaction time task was used. In each trial, an auditory stimulus was presented to the left ear, to the right ear, or simultaneously to both ears. The physical difference between auditory stimuli presented to the two ears was systematically increased across experiments. No redundancy gains were observed when the stimuli were identical pure tones or pure tones of different frequencies (Experiment 1). A clear redundancy gain and evidence of coactivation were obtained, however, when one stimulus was a pure tone and the other was white noise (Experiment 2). Experiment 3 employed a two-alternative forced choice localization task and provided evidence that dichotically presented pure tones of different frequencies are apparently integrated into a single percept, whereas a pure tone and white noise are not fused. The results extend previous findings of redundancy gains and coactivation with visual and bimodal stimuli to the auditory modality. Furthermore, at least within this modality, the results indicate that redundancy gains do not emerge when redundant stimuli are integrated into a single percept.

CognitiveTask

PRP

10.1111/j.1467-9280.2007.01855.x

Psychological science

Psychol Sci

Dorsal and ventral processing under dual-task conditions.

It is widely acknowledged that visual input is processed along two anatomically and functionally distinct pathways--a ventral pathway for conscious perception and a dorsal pathway for action control. The present study investigated whether the apparent direct and unmediated processing in the dorsal stream is subject to capacity limitations. Specifically, we tested whether a simple dorsal task of grasping an object is affected by the psychological refractory period (PRP), a well-known indication of capacity limitations. Subjects performed an auditory choice reaction task and then, following varying delays, had to judge an object's width (ventral task) or grasp an object across its width (dorsal task). Although these tasks were differentially affected by irrelevant variation of the objects' length, they were subject to comparable dual-task interference. These results show that despite important differences between ventral and dorsal information processing, both modes of processing are constrained by limited capacities.

CognitiveTask

PRP

10.1111/j.1469-8986.2007.00513.x

Psychophysiology

Psychophysiology

Adaptive control of event integration: evidence from event-related potentials.

We investigated whether it is possible to control the temporal window of attention used to rapidly integrate visual information. To study the underlying neural mechanisms, we recorded ERPs in an attentional blink task, known to elicit Lag-1 sparing. Lag-1 sparing fosters joint integration of the two targets, evidenced by increased order errors. Short versus long integration windows were induced by showing participants mostly fast or slow stimuli. Participants expecting slow speed used a longer integration window, increasing joint integration. Difference waves showed an early (200 ms post-T2) negative and a late positive modulation (390 ms) in the fast group, but not in the slow group. The modulations suggest the creation of a separate event for T2, which is not needed in the slow group, where targets were often jointly integrated. This suggests that attention can be guided by global expectations of presentation speed within tens of milliseconds.

CognitiveTask

PRP

10.3758/bf03194020

Psychonomic bulletin & review

Psychon Bull Rev

Eye movements, not hypercompatible mappings, are critical for eliminating the cost of task set reconfiguration.

Residual switch costs are notoriously difficult to eliminate. Yet Hunt and Klein (2002) eliminated them in a task that required observers to alternate between 8 trials of prosaccades and 8 trials of antisaccades, as long as there was at least 1 sec between the task cue and the onset of the saccade target. It was proposed that the elimination of residual switch costs occurred because prosaccade responses are computed very rapidly. These so-called hypercompatible responses bypass memory retrieval stages of the response process, thereby eliminating the source of residual switch costs. Here we tested this hypothesis by requiring observers to alternate between responding with the finger that was vibrated (another task that meets the criteria for hypercompatibility) and responding with the finger of the opposite hand. Residual switch costs were not eliminated, suggesting that their elimination in Hunt and Klein (2002) was due to special properties of the prosaccade-antisaccade task.

CognitiveTask

PRP

10.1037/0096-1523.33.1.124

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Visual search is postponed during the attentional blink until the system is suitably reconfigured.

J. S. Joseph, M. M. Chun, and K. Nakayama (1997) found that pop-out visual search was impaired as a function of intertarget lag in an attentional blink (AB) paradigm in which the 1st target was a letter and the 2nd target was a search display. In 4 experiments, the present authors tested the implication that search efficiency should be similarly impaired (steeper search slopes at shorter lags). A conventional AB deficit was found, but, contrary to expectations, search slopes were invariant with lag. These results suggest that no search can be carried out during the period of the AB. Instead, the search is postponed until after the 1st target has been processed. The authors conclude that efficient visual search cannot be carried out unless the visual system is configured appropriately for the search task. If the initial configuration is inappropriate, processing of the 2nd target is held in abeyance until the system has been suitably reconfigured.

CognitiveTask

PRP

10.1097/01.wnp.0000240871.37986.63

Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society

J Clin Neurophysiol

Human high frequency somatosensory evoked potential components are refractory to circadian modulations of tonic alertness.

The impact of vigilance states, such as sleep or arousal changes, on the high-frequency (600 Hz) components (HFOs) of somatosensory evoked potentials (SEPs) is known. The present study sought to characterize the effects of circadian fluctuations of tonic alertness on HFOs in awake humans. Median nerve SEPs were recorded at four times during a 24-hour waking period. In parallel to the SEP recordings, a reaction-time (RT) task was performed to assess tonic alertness. Additionally, the spontaneous EEG was monitored. The low-frequency SEP component N20 and the early and late HFO parts did not change across the measurement sessions. In contrast, RTs were clearly prolonged at night and on the second morning. EEG also showed increased delta power at night. HFOs are sensitive to pronounced vigilance changes, such as sleep, but are refractory to fluctuations of tonic alertness. Tonic alertness is regarded to be the top-down cognitive control mechanism of wakefulness, whereas sleep is mediated by overwhelming bottom-up regulation, which seems apparently more relevant for, at least in part, subcortically triggered high-frequency burst generation in the ascending somatosensory system.

CognitiveTask

PRP

10.1037/0096-1523.32.6.1303

Journal of experimental psychology. Human perception and performance

J Exp Psychol Hum Percept Perform

Reading aloud is not automatic: processing capacity is required to generate a phonological code from print.

The present experiments tested the claim that phonological recoding occurs "automatically" by assessing whether it uses central attention in the context of the psychological refractory period paradigm. Task 1 was a tone discrimination task and Task 2 was reading aloud. The joint effects of long-lag word repetition priming and stimulus onset asynchrony (SOA) were underadditive in Experiment 1, suggesting that an early component of lexical processing does not use central attention. In contrast, nonword letter length and grapheme-phoneme complexity yielded additive effects with SOA in Experiments 2, 3, and 4, suggesting that assembled phonology uses central attention. Further, orthographic neighborhood density also yielded additive effects with SOA in Experiments 5, 6, and 7, suggesting that lexical contributions to phonological recoding use central attention. Taken together, the results of these experiments are inconsistent with the widespread claim that phonological codes are assembled and/or addressed automatically. It is suggested that "automaticity" should be replaced by accounts that make more specific claims about how processing unfolds.

CognitiveTask

PRP

10.1017/s095457940606041x

Development and psychopathology

Dev Psychopathol

Translating basic attentional paradigms to schizophrenia research: reconsidering the nature of the deficits.

Abnormalities in attention have long been viewed as one of the fundamental underlying cognitive deficits in schizophrenia, likely contributing both to formation of some types of symptoms and particularly to the substantial work and social impairments that often accompany schizophrenia. Yet, the precise nature of the attentional deficits in schizophrenia remains poorly understood. Translating advances in cognitive psychology to clinical research brings paradigms with greater analytic power to the study of attention in schizophrenia. In particular, these paradigms should shed light on whether the attentional dysfunction in schizophrenia is best conceptualized as arising from limitations in amount or allocation of processing capacity or from more specific structural bottlenecks that do not allow certain processes to be carried out in two tasks simultaneously. Certain types of dual-task paradigms are particularly well suited to make distinctive predictions, particularly those involving a psychological refractory period paradigm. The background and design of a series of ongoing studies of prodromal, first-episode, and chronic schizophrenia patients are described that are addressing the developmental course of attentional dysfunction in this disorder. These refined paradigms should substantially increase our understanding of the specific forms of attentional impairment characterizing schizophrenia and their connections to symptom development and functional outcome.

CognitiveTask

PRP

10.1037/1064-1297.14.4.450

Experimental and clinical psychopharmacology

Exp Clin Psychopharmacol

Clubgoers and their trendy cocktails: implications of mixing caffeine into alcohol on information processing and subjective reports of intoxication.

Alcoholic drink preferences in college students have made an interesting shift recently, with trends in consumption leaning toward caffeinated alcohol in various forms (e.g., Red Bull and vodka or caffeinated beers such as Anheuser-Busch's B-to-the-E). Despite the dramatic rise in popularity of these beverages, little research has examined the combined effects of alcohol and caffeine, which is problematic for adequately informing the public about the risk or lack thereof of these drinks. The purpose of this study was to directly investigate the acute effects of alcohol and caffeine, alone and in combination, on well-validated measures of cognitive performance and subjective intoxication in social drinkers. Participants (N = 12) performed a psychological refractory period task that measured dual-task interference as the prolonged reaction time to complete the 2nd of 2 tasks performed in close temporal sequence. Performance was tested under 2 active doses and 1 placebo dose of caffeine (0.0 mg/kg, 2.0 mg/kg, and 4.0 mg/kg) in combination with 1 active dose and 1 placebo dose of alcohol (0.0 g/kg and 0.65 g/kg). As expected, alcohol impaired task performance by increasing dual-task interference and increasing errors. The coadministration of caffeine counteracted the effects of alcohol on interference but had no effect on the degree to which alcohol increased errors. Subjective measures of intoxication showed that coadministration of caffeine with alcohol reduced participants' perceptions of alcohol intoxication compared with administration of alcohol alone. The results highlight the complexity of drug interactions between alcohol and caffeine.

CognitiveTask

PRP

10.1007/s00426-006-0100-4

Psychological research

Psychol Res

Attentional awakening: gradual modulation of temporal attention in rapid serial visual presentation.

Orienting attention to a point in time facilitates processing of an item within rapidly changing surroundings. We used a one-target RSVP task to look for differences in accuracy in reporting a target related to when the target temporally appeared in the sequence. The results show that observers correctly report a target early in the sequence less frequently than later in the sequence. Previous RSVP studies predicted equivalently accurate performances for one target wherever it appeared in the sequence. We named this new phenomenon attentional awakening, which reflects a gradual modulation of temporal attention in a rapid sequence.

CognitiveTask

PRP

10.3758/bf03193882

Psychonomic bulletin & review

Psychon Bull Rev

The locus of temporal preparation effects: evidence from the psychological refractory period paradigm.

In reaction time (RT) tasks, responses are especially fast when participants can anticipate the onset of an imperative response signal. Although this RT facilitation is commonly attributed to temporal preparation, it is unclear whether this preparation shortens the duration of early or late processes. We used the effect propagation property of the psychological refractory period paradigm to localize the effect of temporal preparation. Manipulation of temporal uncertainty affected the RT of Task 1, regardless of the level of stimulus onset asynchrony (SOA). Consistent with the prediction of an early locus of temporal preparation, this effect propagated completely to the RT of Task 2 at short SOAs, but propagation diminished virtually to zero at long SOAs.

CognitiveTask

PRP

10.1111/j.1467-9280.2006.01783.x

Psychological science

Psychol Sci

Motor limitation in dual-task processing under ballistic movement conditions.

The standard bottleneck model of the psychological refractory period (PRP) assumes that the selection of the second response is postponed until the first response has been selected. Accordingly, dual-task interference is attributed to a single central-processing bottleneck involving decision and response selection, but not the execution of the response itself. In order to critically examine the assumption that response execution is not part of this bottleneck, we systematically manipulated the temporal demand for executing the first response in a classical PRP paradigm. Contrary to the assumption of the standard bottleneck model, this manipulation affected the reaction time for Task 2. Specifically, reaction time for Task 2 increased with execution time for Task 1. This carryover effect from Task 1 to Task 2 provides evidence for the notion that response execution can be part of the processing bottleneck.

CognitiveTask

PRP

10.1371/journal.pbio.0040220

PLoS biology

PLoS Biol

Dynamics of the central bottleneck: dual-task and task uncertainty.

Why is the human brain fundamentally limited when attempting to execute two tasks at the same time or in close succession? Two classical paradigms, psychological refractory period (PRP) and task switching, have independently approached this issue, making significant advances in our understanding of the architecture of cognition. Yet, there is an apparent contradiction between the conclusions derived from these two paradigms. The PRP paradigm, on the one hand, suggests that the simultaneous execution of two tasks is limited solely by a passive structural bottleneck in which the tasks are executed on a first-come, first-served basis. The task-switching paradigm, on the other hand, argues that switching back and forth between task configurations must be actively controlled by a central executive system (the system controlling voluntary, planned, and flexible action). Here we have explicitly designed an experiment mixing the essential ingredients of both paradigms: task uncertainty and task simultaneity. In addition to a central bottleneck, we obtain evidence for active processes of task setting (planning of the appropriate sequence of actions) and task disengaging (suppression of the plan set for the first task in order to proceed with the next one). Our results clarify the chronometric relations between these central components of dual-task processing, and in particular whether they operate serially or in parallel. On this basis, we propose a hierarchical model of cognitive architecture that provides a synthesis of task-switching and PRP paradigms.

CognitiveTask

PRP

10.1007/s00426-006-0070-6

Psychological research

Psychol Res

Exploring the mental number line: evidence from a dual-task paradigm.

In a parity-judgment task smaller numbers are responded to faster with the left-hand key and vice versa for larger numbers (SNARC effect; Dehaene et al., in Journal of Experimental Psychology: General, 122, 371-396, 1993). We used the psychological refractory period paradigm involving a parity-judgment task and tone-discrimination task to address the question at which stage this effect arises. When the parity-judgment task is performed second, then we found equal SNARC effects for the short and the long SOA. According to the central bottleneck model, this indicates that the effect arises during the response-selection or execution stage. In Experiment 2 the parity-judgment task was performed first. The pattern of results indicates that the SNARC effect originates during the perceptual encoding or response-selection. Together, our results suggest that the SNARC effect originates while the response is selected.

CognitiveTask

PRP

10.1007/s00426-006-0066-2

Psychological research

Psychol Res

Is the psychological refractory period effect for ideomotor compatible tasks eliminated by speed-stress instructions?

It has been argued that the psychological refractory period (PRP) effect is eliminated with two ideomotor compatible tasks when instructions stress fast and simultaneous responding. Three experiments were conducted to test this hypothesis. In all experiments, Task 1 required spatially compatible manual responses (left or right) to the direction of an arrow, and Task 2 required saying the name of the auditory letter A or B. In Experiments 1 and 3, the manual responses were keypresses made with the left and right hands, whereas in Experiment 2 they were left-right toggle-switch movements made with the dominant hand. Instructions that stressed response speed reduced reaction time and increased error rate compared to standard instructions to respond fast and accurately, but did not eliminate the PRP effect on Task 2 reaction time. These results imply that, even when response speed is emphasized, ideomotor compatible tasks do not bypass response selection.

CognitiveTask

PRP

10.1080/02724980543000060

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

Dual route for subtask order control: Evidence from the psychological refractory paradigm.

A change in subtask order in the psychological refractory period (PRP) paradigm increases the effect of stimulus onset asynchrony (SOA) on the second response. We used a paradigm with cued, randomly determined subtask order to test the hypothesis that this SOA by order switch overadditivity reflects order control, via "copying" stimulus order. In Experiments 1a and 1b, overadditivity was evident only with insufficient opportunity for cue-based order control. In Experiment 2, overadditivity was decreased by using the same set of stimuli in the two subtasks, presumably by removing the opportunity to rely on stimulus order. In Experiment 3, removing the order cue increased the overadditivity, presumably because control was based solely upon copying stimulus order. The results indicate interactive top-down and bottom-up order control. Implications to theories of the PRP paradigm are discussed.

CognitiveTask

PRP

10.1080/02724980543000015

Quarterly journal of experimental psychology (2006)

Q J Exp Psychol (Hove)

On the locus of dual-task interference: Is there a bottleneck at the stimulus classification stage?

Recent studies have provided evidence that dual-task interference is typically caused by a single-channel bottleneck, but the processing locus of the bottleneck has yet to be pinned down. A bottleneck locus at the response-selection stage is widely advocated, but an earlier locus would be consistent with most previous evidence. Four new experiments used the "locus of slack" method to investigate whether the stages postponed by the central bottleneck include stimulus classification, a very late stage of perceptual processing. The experiments varied stimulus classification difficulty for two different analogueue perceptual judgements. Experiment 1 found only modest absorption into slack for the difficulty of a spatial position judgement. Experiments 2-4 found virtually no absorption into slack for the difficulty of a box-width judgement. These results support a bottleneck locus beginning at or before the stage of stimulus classification and hence prior to the stage of response selection. Other evidence, however, leaves no doubt that response selection is also subject to bottleneck postponement. Two architectures are discussed that can account parsimoniously for both old and new results. One posits a single bottleneck resulting from a unified CPU-like central processor; the other posits multiple bottlenecks resulting from multiple processors accomplishing different substages of central processing.

CognitiveTask

PRP