Conditioned responding extinguishes more slowly after partial (inconsistent) reinforcement than after consistent reinforcement. This Partial Reinforcement Extinction Effect (PREE) is usually attributed to learning about nonreinforcement during the partial schedule. An alternative explanation attributes it to any difference in the rate of reinforcement, arguing that animals can detect the change to nonreinforcement more quickly after a denser schedule than a leaner schedule. Experiments 1a and 1b compared extinction of magazine responding to a conditioned stimulus (CS) reinforced with one food pellet per trial and a CS reinforced with two pellets per trial. Despite the difference in reinforcement rate, there was no reliable difference in extinction. Both experiments did demonstrate the conventional PREE comparing a partial CS (50% reinforced) with a consistent CS. Experiments 2 and 3 tested whether the PREE depends specifically on learning about nonreinforced trials during partial reinforcement. Rats were trained with two CS configurations, A and AX. One was partially reinforced, the other consistently reinforced. When AX was partial and A consistent, responding to AX extinguished more slowly than to A. When AX was consistent and A was partial, there was no difference in their extinction. Therefore, pairing X with partial reinforcement allowed rats to show a PREE to AX that did not generalise to A. Pairing A with partial reinforcement meant that rats showed a PREE to A that generalised to AX. Thus, the PREE depends on learning about nonreinforced trials during partial reinforcement and is not due to any difference in per-trial probability of reinforcement
The partial reinforcement extinction effect depends on learning about nonreinforced trials rather than reinforcement rate.