Discrimination along a size continuum following ablation of the inferior temporal convexity in monkeys.

Abstract

To account for visual discrimination impairment in monkeys with temporal lobe lesions, it has been suggested that such ablations interfere with an essential nonvisual function, termed a "comparison attitude." It is argued from such a hypothesis that no loss in discriminating would arise between a particular pair of stimuli, provided the operated animals had first learned to discriminate with perfect accuracy between other stimuli differing in the same dimension. To test this prediction, operated animals and nonoperate controls were trained to discriminate a large difference in visual size and were then presented with a graded series in which the difference was gradually reduced. Although the temporal operates rapidly attained the criterion of 100% correct on the initial size discrimination, their scores on the subsequent (more difficult) discriminations fell significantly below the scores achieved by the nonoperate controls. This impairment may be expressed as an increased difference limen for visual size. The finding does not support the view that a loss of a "comparison attitude" accounts for the visual discrimination impairment of temporal operates.