Loss of associability by a compound stimulus comprising excitatory and inhibitory elements

In each of two experiments rats learned a discrimination between a stimulus (A) that signaled shock and a compound stimulus (AB) that signaled no shock. In Experiment 1 it was found that the AB compound acquired excitatory strength only slowly when, in a second phase of training, it was made to signal the occurrence of shock. In Experiment 2 the acquisition of inhibitory strength by the compound was similarly found to be retarded. This second experiment also replicated the results of Experiment 1. The relevance of these results to current theories of latent inhibition and attention is discussed.