Classical conditioning of the rabbit nictitating membrane response can be fast or slow : Implications for Lennartz and Weinberger ' s ( 1992 ) two - factor theory

Classical conditioning of the rabbit's nictitating membrane (NM) response usually requires several dozen trials for the first conditioned response (CR) to appear. However, as the number of trials is reduced to one per session, the rate of acquisition increases progressively, and the first CR appears in less than a dozen trials. This large and systematic variation in the rate of conditioning challenges recent conclusions by Lennartz and Weinberger (1992). They use the rabbit NM preparation as an example of a slow-conditioning, "specific" system that is distinct from a fast-conditioning, "nonspecific" system, such as heart rate.