Differential effects of omission contingencies on various components of Pavlovian appetitive conditioned responding in rats

Five experiments with rat subjects investigated the effects of omission and partial reinforcement contingencies on five individual behaviors evoked by visual and auditory conditioned stimuli paired with a food unconditioned stimulus. The effects of omission depended on the behavior on which that contingency was placed: One behavior was eliminated, one was unaffected, and three were reduced relative to the performance of yoked controls. Partial reinforcement resulted in lower frequencies of three behaviors and higher frequencies of two behaviors, compared with performance under consistent reinforcement. A partial reinforcement extinction effect was noted with one behavior but not with the others. These results are related to the possible role of instrumental conditioning contingencies in generating conditioned behavior in this appetitive conditioning preparation and to the independence of individual components of a complex conditioned response.