Abstract
Non-profile views of point-light biological motion convey a clear impression of the direction in depth in which the actor faces. This is even the case if no explicit depth cues, such as disparity or perspective, are added to the display. We asked how well normal human subjects can judge the facing in depth of point-light walking. We found that subjects were quite proficient at this task. Minor errors consisted of hysteresis errors around the profile and frontal views, a systematic bias toward the profile view and variable errors. We then asked which cues are most important in the judgment of the facing direction. For this we employed five different manipulation on the point light stimuli: reversed (backward) walking, scrambling in time, scrambling in the phase of the joint-movements, scrambling in the phase of the point-movements (rubber-like), scrambling in spatial position. The facing in depth of these stimuli was increasingly difficult to judge, showing that different aspects of the point light motion contribute differently to the depth percept.