Visual discrimination impairments following lesions of the superior temporal sulcus are not specific for facial stimuli.

Six rhesus monkeys took part in an experiment on visual learning. In three of the monkeys the part of the superior temporal sulcus in which many of the cells respond selectively to some aspect of faces was removed, while the remaining three animals served as unoperated controls. In Experiment 1 they learned a series of two-choice visual discriminations between patterns. The animals with lesions of the superior temporal sulcus were markedly impaired. The discriminations were of two types: in the first, the discriminanda differed in shape (e.g. Y and 3), while in the second they differed only in their orientation (e.g. <and>). Unlike animals with lesions to the neighbouring inferior temporal cortex who are impaired on shape but not orientation discriminations, animals with lesions of the superior temporal sulcus were equally impaired on both types of discrimination. In Experiment 2 the same six animals learned a series of discriminations between discriminanda which consisted of photographs of pairs of eyes. Each discrimination was between a set of eyes which looked directly at the viewer and a set in which the gaze was laterally averted to varying degrees. Again, animals with lesions of the superior temporal sulcus showed a marked impairment. We conclude that this impairment may be a general impairment in two-choice visual discrimination learning, rather than a selective impairment in discrimination of eye gaze. This result warns against a simple interpretation of the function of this area as a "face area", concerned only, or chiefly, with the perception and significance of parts of the body, notably faces, and their movements.