Visual search for moving and stationary items in chimpanzees (Pan troglodytes) and humans (Homo sapiens)

Four visual search experiments were conducted using human and chimpanzee subjects to investigate attentional processing of movement, and perceptual organization based on movement of items. In the first experiment, subjects performed visual searches for a moving target among stationary items, and for a stationary target among moving items. Subjects of both species displayed an advantage in detecting the moving item compared to the stationary one, suggesting the priority of movement in the attentional processing. A second experiment assessed the effect of the coherent movement of items in the search for a stationary target. Facilitative effects of motion coherence were observed only in the performance of human subjects. In the third and fourth experiments, the effect of coherent movement of the reference frame on the search for moving and stationary targets was tested. Related target movements significantly influenced the search performance of both species. The results of the second, third, and fourth experiments suggest that perceptual organization based on coherent movements is partially shared by chimpanzees and humans, and is more highly developed in humans.