COMPARATOR MECHANISMS AND CONDITIONED INHIBITION - CONDITIONED-STIMULUS PREEXPOSURE DISRUPTS PAVLOVIAN CONDITIONED INHIBITION BUT NOT EXPLICITLY UNPAIRED INHIBITION

Three conditioned lick-suppression experiments with rats examined the effects of pretraining exposure to the conditioned stimulus (CS) on be havior indicative of conditioned inhibition. After CS-preexposure trea tment, subjects received either Pavlovian conditioned inhibition train ing or explicitly unpaired inhibition training with the preexposed CS. The inhibitory status of the CS was then assessed with a retardation (Experiment 1) or a summation (Experiment 2) test. Experiment 3 contro lled for the unconditioned stimulus-preexposure effect being a potenti al confound in Experiments 1 and 2: As predicted by the comparator hyp othesis (R. R. Miller gr L. D. Matzel, 1988), the CS-context associati on that developed during the CS-preexposure phase disrupted the expres sion of Pavlovian conditioned inhibition but not the expression of exp licitly unpaired inhibition.