| Abstract: | Pigeons were trained in discriminations where S+ and S? shared common visual elements but were distinguished by the presence or absence of a visual feature. When S+ contained the distinctive feature (the feature-positive condition), the pigeons rapidly learned to withold responses to S?: The learning rate was not markedly affected by changes in the relative size of the feature and the common element. When S? contained the distinctive feature (the feature-negative condition), the pigeons learned to withhold responses to S? more rapidly when the feature was large relative to the common element than when the feature was small relative to the common element. This effect was observed when the stimuli were present at the locus of response and when the stimuli were remote from the locus of response. To explain these results, and the results of generalization tests, it was proposed that the effectiveness of the feature in suppressing responding to the common element during feature-negative training depended on the relative size of the feature and the common element. |
