Perceiving the Actions of Other People

What is responsible for the commonality of perception across individuals? This article examines this question from an ecological perspective, beginning with Gibson's (1979/1986) conception of the optic array, which establishes that information about the world is public, that is, available to any observer. Experiments on sitting, bipedal climbing, stepping across gaps, and reaching showed that observers were able to perceive critical action boundaries for other people as accurately as they did for themselves. For each action the obtained critical boundaries were invariant across diverse actors when expressed in terms of relevant aspects of the prospective actor's body scale. This was true when observers judged their own action capabilities as well as when they judged the capabilities of other people. Two additional experiments examined observers' ability to perceive someone else's intention from seeing another person's actions. These experiments provide additional support for Runeson and Frykholm's (1981, 1983) kirematics specifies dynamics principle. Together these findings show that observers can make accurate judgments about the action capabilities and intentions of other people as they perform goal-directed actions. This outcome is consistent with the prediction from Gibson's notion that information is public. Thus, the commonality of perceptual experience among people is the result of the public availability of information about what the environment affords a prospective actor.