Abstract
Perception-action theories suggest that observers use their own action control systems to perceive the actions of others. If so, then observers must be able to overlook form differences between their body and the bodies of other people. Furthermore, observers should be able to recognize their actions in the absence of body form cues. To test these ideas, two psychophysical studies of identity perception were conducted. Observers demonstrate the greatest visual sensitivity to their own movements in point light displays (Loula et. al, 2005). Form cues are reduced in point light displays, but are not absent. Optic flow patterns are devoid of bodily form cues. In Experiment 1, naïve participants walked along a hallway with a head mounted camera. The resultant optic flow stimuli were edited into 5 sec movies. One month later, participants viewed the optic flow stimuli that they and another person had generated. In a 2AFC task, participants differentiated their own flow patterns from those of another person at above chance levels, suggesting that identity perception can occur independently of body form. To extend this result, Experiment 2 tested whether participants can identify their own actions even when those actions are presented on someone else's body. Participants' actions were recorded with a motion capture system and superimposed onto different bodies. One month later, participants identified the actor in each movie. Performance in this identity discrimination task depended upon motion but not body shape. Together, these findings support motor theories of action perception that emphasize actions over bodies.