Rapidly developed scalar timing in unsignalled shuttlebox avoidance learning

Three groups of rats were given brief inescapable shocks in a shuttlebox with equal shock-shock (S-S) and response-shock (R-S) intervals of 10, 15 or 20 s. Non shock-elicited responses (experimentally defined) postponed the occurrence of the next shock while shock elicited responses had no programmed consequences. Avoidance behaviour was rapidly acquired with all groups avoiding 85% or more of scheduled shocks by the end of the fifth 1 h session. Interresponse times revealed the development of excellent temporal discriminations in all groups. The data provide quantitative support for Gibbon's (1971) scalar timing hypothesis.