The sequencing of trials during partial reinforcement affects subsequent extinction

If a conditioned stimulus or response has been inconsistently ("partially") reinforced, conditioned responding will take longer to extinguish than if responding had been established by consistent ("continuous") reinforcement. This partial reinforcement extinction effect (PREE) is one of the best-known phenomena in associative learning but defies ready explanation by associative models which assume that a partial reinforcement schedule will produce weaker conditioning that should be less resistant to extinction. The most popular explanation of the PREE is that, during partial reinforcement, animals learn that recent nonreinforced (N) trials are associated with subsequent reinforcement (R), and therefore the presence of N trials during extinction serves to promote generalization of conditioning to extinction. According to sequential theory (Capaldi, 1966), animals can encode whole sequences (runs) of N trials and associate their memory of the sequence with subsequent R. The length of these N sequences during conditioning affects how long the animal will continue to respond during extinction. The present experiment used Pavlovian magazine approach conditioning with rats to test two predictions of this theory. Consistent with sequential theory, the PREE was sensitive to the length of the N sequence: conditioning with long sequences (runs of 3-5 N trials) produced a stronger PREE than conditioning with short sequences (runs of 1 or 2) even when the total number of N and R trials was held constant. Surprisingly, there was no PREE among rats trained with the short sequences. Moreover, contrary to the theory's prediction, interrupting the long N sequences with reinforced trials of a different conditioned stimulus did not affect the subsequent PREE. I conclude that uncertainty about reinforcement, rather than the memory of N sequences per se, is a key factor in the development of the PREE. (PsycInfo Database Record (c) 2024 APA, all rights reserved).