Biological Motion Perception of the Moving Point-Lights Generated by Human Hand Movements
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Point-light sources were fixed on the surface of a leather glove made thin and well-fitted to the fingers of the actor's right hand. Those point-lights were placed on a position corresponding to each joint of his fingers. In a dark room they became bright and appeared as a moving pattern of point-lights in an otherwise darkness. When the actor moved his hand, those moving point-lights were perceived as very odd, even quite horrible. Try to imagine that, in a dark room, a person moves his hand to and fro, stretching it towards you by making the fingers closing and opening, and you can see nothing but the moving point-lights generated by the movement of his invisible hand. How strange these moving point-lights will be to you! Indeed the observers often told me about the strangeness of their appearance. However they also could recognize a clear image of "human hand movements" (Johansson, 1973). Then I wondered where the difference in their perceptions between nonhuman-like motion and human-like action came from (Cutting, Proffitt, & Kozlowski, 1978; Johansson, 1973; Runeson, 1981; Sumi, 1984).