The gender-based facing bias in 3-D biological motion perception

In biological motion perception, movements of several point lights can evoke a vivid impression of living animals, including humans. Recent studies have reported that male point-light walkers tend to be perceived as facing toward the viewer more than female walkers, and have hypothesized that the gender-based facing bias arises from motion signals. The purpose of this study was to test this hypothesis under experimental conditions where binocular disparity was added to biological motion stimuli. In the two experiments reported here, participants were presented with disparity-defined female and male point-light figures facing toward or away from the viewer. In Experiment 1, we measured "facing-the-viewer" responses in upright and inverted walker configurations. It was found that the facing bias was greater for the male walker than for the female walker in most disparity magnitudes, regardless of walker inversion. In Experiment 2, the walker stimuli were replaced by static snapshots of the walkers. The results showed that the facing bias did not differ between the female and male static figures. These results suggest that motion signals play an important role in producing the gender-based facing bias, even when binocular disparity is added to biological motion stimuli.