Determinants of value transfer and contrast in simultaneous discriminations by pigeons

Abstract

In a simultaneous discrimination involving a positive (S+) and a negative (S−) stimulus, positive value appears to transfer from the S+ to the S−. However, negative value does not appear to transfer from the S− to the S+. Instead, when sufficient experience with the contingencies associated with responding to the S− is provided, it appears that the presence of the S− enhances the value of the S+ (i.e., a contrast effect is found). The purpose of the present experiments was to further examine the influence of the S+ on the S− in a simultaneous discrimination (between subjects in Experiment 1 and within subjects in Experiment 2). In both experiments, we found that under typical training conditions, given little direct experience with the value of the S−, value transfers from the S+ to the S−. If sufficient experience with the value of the S− is provided, however, contrast between the S+ and the S− can be demonstrated. Thus, in a simultaneous discrimination, value transfer from the S+ to the S− depends on the animal’s having responded relatively little to the S−.