Abstract
We sought to investigate sources of intersubject variability in the use form and motion cues during biological motion perception. We administered a battery of psychophysical and cognitive tasks to assess the relationship between sensitivity of these perceptual mechanisms and other behavioral measures. Discriminating facing direction of a point light walker can be achieved using form cues alone, whereas discriminating walking direction cannot (Lange & Lappe, 2007). In order to differentiate between form and motion processing, we administered both of these tasks to the same individuals (plus non-biological object motion controls). Point-light stimuli were embedded in a variable number of noise dots, and subjects had to determine which direction the target faced or moved (depending on the task). Thresholds were estimated adaptively (Watson & Pelli, 1983). The tasks in our battery included perceptual measures such as motion coherence thresholds, visual and motor imagery, and measurements of social traits such as empathy and personality. We hypothesized that tasks sharing perceptual and neural resources with the mechanisms for biological form and motion processing would correlate significantly with perceptual sensitivity as measured by our tasks. The walking direction task, which relies on motion processing, significantly correlated with third-person visual motor imagery. Non-biological object motion direction also correlated with this measure. However, no significant correlations were found with non-motor visual imagery. In line with embodied theories of action perception, first-person visual motor imagery was significantly correlated with the biological walking direction task, but not its non-biological counterpart. No significant correlations were observed for the facing direction experiments, providing evidence that different perceptual resources contribute to form and motion processing in biological motion perception.
Meeting abstract presented at VSS 2012