Perception of animacy from the motion of a single object

We demonstrate that a single moving object can create the subjective impres sion that it is alive, based solely on its pattern of movement. Our display s differ from conventional biological motion displays (which normally invol ve multiple moving points, usually integrated to suggest a human form) in t hat they contain only a single rigid object moving across a uniform field. We focus on motion paths in which the speed and direction of the target obj ect change simultaneously. Naive subjects' ratings of animacy were signific antly influenced by (i) the magnitude of the speed change, (ii) the angular magnitude of the direction change, (iii) the shape of the object, and (iv) the alignment between the principal axis of the object and its direction o f motion. These findings are consistent with the hypothesis that observers classify as animate only those objects whose motion trajectories are otherw ise unlikely to occur in the observed setting.