A Social Visual System?

Previous research suggests that the human visual system may be finely tuned for the pick up of social information. For example, observers can accurately and readily determine the emotional state, deceptive intent, effort, and vulnerability of individuals from the highly degraded motion cues available in point-light displays of their action. Furthermore, some researchers have even suggested that social processes constrain the neural architecture of perceptual systems (e.g., Brothers, 1997). To test the hypothesis that the social information can constrain visual processes, we conducted a series of apparent motion and change blindness studies. In our apparent motion studies, observers viewed two frames of a moving person across variations in temporal display rate (ISI). In the human context condition, a second stationary person was added to the display. In the object context condition, a stationary, action appropriate object was added to the display. In the no context condition, only the moving person was shown. Subjects' ratings of apparent motion quality suggested that they perceived significantly more compelling motion in the human context condition. This finding is consistent with the hypothesis that social information can enhance visual motion analyses. A change blindness study examined the role of attention in these processes. Change detection rates were compared for actor movements of social relevance and for socially irrelevant actor features. Changes in actor movement, whether emotional or gait-based, were better detected than changes in unknown actors' clothes or identities. Since human movement carries important social information, these findings suggest that attentional deployment is constrained by fundamental social requirements such as the need to know what other people are doing. Thus, attention may selectively enhance the visual analysis of human behaviors. Such conclusions support the hypothesis of a socially tuned visual system.