Latent inhibition: a review and a new hypothesis.

A review of research regarding the deleterious effects of stimulus preexposure upon subsequent learning is presented. The investigations are discussed with respect both to the generality of this phenomenon and variables controlling its magnitude. Complementary experiments are suggested. Theoretical interpretations are critically reviewed. It is concluded that some of the hypotheses are too narrow to explain the existing data, and some of them lead to predictions which are contrary to the existing data. A new hypothesis is proposed suggesting that during the stimulus preerxposure phase the subject learns a "zero correlation" between the stimulus, or his own behavior and other environmental contingencies. When new learning contingencies are imposed the subject must first unlearn the "zero correlation" learned during preexposure. This process of unlearning retards the learning of the new contingency.