Backward conditioning: A reevaluation of the empirical evidence.

There is an apparent discrepancy between the widespread view that backward conditioning does not occur and the experimental evidence which suggests that it does. Backward pairing of conditioned and unconditioned stimuli frequently has resulted in effects similar to those produced by forward pairing, and the results of several recent experiments have established that such effects cannot be attributed to factors other than stimulus pairing per se. Surprisingly, even some of the earlier experiments that provided the basis for the current skepticism concerning backward conditioning provide evidence of its existence. The failure to recognize backward conditioning as a legitimate phenomenon seems to reflect theoretical biases rather than a paucity of empirical evidence. Thus backward conditioning and its properties merit renewed interest and rcexamination. In a recent experiment by Keith-Lucas and Guttman (1975), rats that received a single footshock followed by the presentation of a toy hedgehog subsequently avoided the