Human efficiency in detecting and discriminating biological motion.

Using an "information meter" provided by ideal observer analysis, we measured the efficiency with which human observers processed different walking stimuli against luminance noise and spatial uncertainty to either detect the presence of a walker or to discriminate the walking direction. Human efficiency was examined across four renderings of a human walker: contour, point lights, silhouette, and skeleton. We replicated the previous finding of low discrimination efficiency in biological motion (Gold, Tadin, Cook, & Blake, 2008) and also found low detection efficiency for biological motion. Interestingly, in both detection and discrimination tasks, the skeleton display was among those yielding the highest level of efficiency in processing visual information. This finding suggests that structural information about the relative position of joints, highlighted in the skeleton display, provides a critical component of the internal representation for biological motion.