Effects of shock contingent on responding during the trace interval on shuttlebox-avoidance learning in Fischer 344 rats

Abstract

Fischer 344 rats were trained with a two-component serial compound conditioning procedure in which a stimulus-free trace interval (termed S2) was interposed between warning signal (WS) termination and shock onset. Thus, all rats had two (WS-S2 and S2-shock) intervals during which they were free to make a shuttle response, and each lasted for 10 s. When the response to WS succeeded in avoiding shock but the response in S2 was punished by the scheduled shock, rats acquired few avoidance responses to WS. In order to test the generality of the results, rats received punishment for the response only to S2 with probability of 0.5 or 1.0, after they had acquired a response either to WS or to S2 in order to avoid shock. There was a progressive decline in the rate of avoidance responding to WS. When an explicit second signal (S −) was used to fill the S2 interval, rats also acquired few avoidance responses to WS when the response only to S − was punished. It seems that an association between WS and shock fails to develop when the effect that the response during WS earns is opposed by punishment of responding in the presence of S2 (or S −).