evidence: ffects of biperiden on the learned irrelevance (LIrr) index (means+s.e.m.). In the placebo condition, intact LIrr is present, reflected by a LIrr index larger than zero. The same holds for the biperiden condition; in other words, biperiden failed to affect LIrr.
intervention: Biperiden
comparator: Placebo
outcome: Learned irrelevance index