International Journal of Comparative Psychology

Pavlovian associative processes appear to be intimately involved in the acquisition of simultaneous discriminations by pigeons. We have found evidence that in a simultaneous discrimination, value transfers from the positive stimulus (S+) to the negative stimulus (S-) and the basis of that transfer appears to be the higher-order association of the S- with the reinforcer, by way of the S+. Furthermore, the association between the S+ and the S- appears to be bidirectional, occurring in the form of a within event association. In addition, it appears that when pigeons have extended experience with the consequences of responding to the Sstimulus, contrast (the opposite of value transfer) develops between the two (e.g., increasing the value of one, decreases the value of the other). Finally, I suggest that versions of simultaneous discriminations may provide a useful model of several Pavlovian conditioning phenomena including, higher-order conditioning, withinevent conditioning, postconditioning devaluation effects, inhibitory conditioning, potentiation, and perhaps also overshadowing.