VARIATION OF CS-US INTERVAL IN LONG-TERM AVOIDANCE CONDITIONING IN RAT WITH WHEEL TURN AND WITH SHUTTLE TASKS

Varied the CS-UCS interval in 2 experiments with a wheel-turn avoidance response, and in 2 experiments with a shuttle response. In both tasks, longer intervals produced better performance, but this difference disappeared in tests at the same interval. Latency distributions, however, had distinct shapes at each CS-UCS interval. In the shuttle task, performance was poor on Day 1 but improved markedly and rapidly on Day 2. In the wheel-turn task, avoidance decrement was substantial at the 2- and 5-sec intervals, though less clear at the 15-sec interval. When the CS was omitted in the final phase of the wheel-box experiments, avoidance frequency continued at about the same level. It is suggested that wheel-turn avoidance develops initially as generalized responding reinforced by UCS termination, and that discriminated responding develops subsequently, through stimulus differentiation and extinction of the generalized intertrial responses. (17 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.