ADJUSTING TO CHANGES IN THE TIME OF REINFORCEMENT - PEAK-INTERVAL TRANSITIONS IN RATS

Thirty rats received training on a peak-interval procedure, where a ba seline with a 20-s time of reinforcement was interspersed among cyclic transitions to other reinforcement time values (10, 20, 30, or 40 s), each of which was either in force for only a single session or for 3 sessions. Peak times were close to the time of reinforcement on the 20 -s baseline and tracked the new reinforcement times both closely (but not exactly) and very rapidly. Peak time during transitions was affect ed by the criterion value in force on the previous session, exhibiting a proactive interference effect. Analysis of individual peak times du ring a session showed that transitions from lower to higher reinforcem ent time values were usually characterized by abrupt jumps in peak tim e, whereas descending transitions were mostly smooth but rapid.