UCS duration and conditioned suppression: Acquisition and extinction between-groups and terminal performance within-subjects

Two experiments demonstrated a positive monotonic relation between UCS duration and conditioned suppression ranging from no suppression at 0.05 sec to nearly complete suppression at 3.0 sec. In Exp 1, 5 acquisition groups were run at 0.5 mA. No suppression occurred at the shortest duration, approximately 50% suppression by Session 3 in two intermediate groups (0.2 and 0.5 sec) and nearly complete suppression by Session 3 at the two longest durations (1.0 and 3.0 sec). The relation between UCS duration and recovery of responding during extinction followed a parallel pattern. In Exp 2, terminal performance was studied within-subjects and the same relation was replicated.