Within-session responding as a function of post-session feedings.

Ten rats pressed levers or keys for food reinforcers delivered by a multiple variable interval schedule. The delay between the end of the session and the delivery of a post-session feeding varied from 0 to 240 minutes. Contrary to the results reported by Bacotti (1976), response rates were not significantly higher when post-session feedings were delayed than when they were immediate. Response rates also increased and then decreased within the session, regardless of the delay to post-session feedings. These results suggest that subjects do not always integrate rewards across locations. Therefore, theories need not always include the temporal location of post-session feedings in the context of variables that determines responding within the session. Experiments must also take care to ensure that changes in response rates within the session do not confound the interpretation of their results.