Visual texture segregation by the chimpanzee (Pan troglodytes)

One adult male chimpanzee (Pan troglodytes) was trained to detect a target area consisting of texture elements from the background texture made of the different elements from the target area. The subject was given eight different stimulus conditions. In Condition 1, segregation was based on the difference of local feature of elements but not on global similarity. Conditions 2-3 investigated the effects of the number of terminators, which was considered as 'textons' in human texture perception. The chimpanzee showed better performance when the discrimination can be based on the difference of the number of terminators. This tendency, however, was reversed when the local salient feature (length of shorter lines) was enhanced, as in Enns' [15] study with humans as subjects. The subject showed asymmetries in segregation performance when discriminating based on gap (Conditions 4-5), line length (Condition 6), and regularity of line arrangement (Condition 7). Observed asymmetries were consistent with humans and with visual search asymmetries. The performance of texture segregation by the chimpanzee was consistent with humans, and the texture segregation is one of the useful tasks for comparative study of early vision as well as visual search task.