Perceiving Direction of a Walker: Effect of Body Appearance

Human can perceive others' walking direction accurately even with 117ms observation (Sato, et al., ECVP2008). We aimed to see whether appearance of walker's body affects the accuracy of perceiving direction of the walker. Thus, we employed three different appearances: realistic human computer-graphics body (CG-human), nonrealistic cylinder-assembled body (Cylinders), and point-light walker (Points). We made a three-dimensional model of an adult-size walker who walked at a place. CG-human stimuli were generated by rendering the model with smooth shading. We made Cylinders stimuli by replacing body parts such as arms, legs, head, and hands with cylinders. Points stimuli were made by tracking 18 positions (mostly joints) of the body like biological motion. One of walkers was presented for 117, 250, 500 or 1000ms while its direction was randomly varied by 3deg steps to 21deg left or right. Observers judged whether the walker was walking toward them (hit) or not (miss), and self-range was measured in terms of the standard deviation for hit distributions. The perceived self-range was narrowed with long duration, and with CG-human stimulus. It is suggested that the accuracy of perceiving walker's direction depends on body appearance, and it is higher for human-like body than nonhuman body.