Resurgence of response sequences during extinction in rats shows a primacy effect.

Rats were trained to emit a series of three-response sequences to a criterion (i.e., more than 80% of all emitted sequences correct over five successive sessions). Each rat was trained on a series of different, three-response sequences. After the final three-response sequence was acquired, two extinction tests were administered, and the three-response sequences that re-emerged during these extinction tests were noted. Resurgence effects during extinction were observed; that is, the previously trained sequences were emitted. These resurgence effects followed an orderly pattern, which involved a primacy effect. The rats initially emitted the immediately previously trained response, but then started to emit the response sequence they first were trained to emit. Thus, resurgence behavior during extinction can be an orderly function of previous training history. These results replicate those previously obtained with human subjects.