The eyes have it: the neuroethology, function and evolution of social gaze

Gaze is an important component of social interaction. The function, evoluti on and neurobiology of gaze processing are therefore of interest to a numbe r of researchers. This review discusses the evolutionary role of social gaz e in vertebrates (focusing on primates), and a hypothesis that this role ha s changed substantially for primates compared to other animals. This change may have been driven by morphological changes to the face and eyes of prim ates, limitations in the facial anatomy of other vertebrates, changes in th e ecology of the environment in which primates live, and a necessity to com municate information about the environment, emotional and mental states. Th e eyes represent different levels of signal value depending on the status, disposition and emotional state of the sender and receiver of such signals. There are regions in the monkey and human brain which contain neurons that respond selectively to faces, bodies and eye gaze. The ability to follow a nother individual's gaze direction is affected in individuals with autism a nd other psychopathological disorders, and after particular localized brain lesions. The hypothesis that gaze following is "hard-wired" in the brain, and may be localized within a circuit linking the superior temporal sulcus, amygdala and orbitofrontal cortex is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.