Abstract
Point-light biological motion stimuli have particular spatiotemporal properties that enable them to be processed with remarkable efficiency. Human observers can readily recognize action, gender, emotion, and identity information conveyed by dynamic point-light walkers. All these processes require temporal integration, yet little is known about the encoding of biological motion temporal information. Here we report a novel temporal illusion: biological motion signals significantly lengthen perceived temporal duration in a manner that is independent of conscious awareness of biological nature. In a parametric time discrimination paradigm, we showed that the same presentation duration of an upright biological motion sequence was perceived significantly longer compared with that of an inverted motion sequence. This overestimation effect was not due to the familiarity of the global configuration, since an upright static biological motion frame showed no difference when compared with an inverted one. Moreover, such temporal illusion persisted with spatially scrambled biological motion signals, whose global configurations were completely disrupted, independent of the observers' explicit knowledge of the nature of the stimuli. These findings provide strong evidence that biological motion has particular temporal properties that distinguish itself from other forms of motion and highlight the intrinsic sensitivity of the human visual system to local biological motion signals.
This research was supported by the Knowledge Innovation Program of Chinese Academy of Sciences (KSCX2-YW-R-248 and 09CX202020) and National Natural Science Foundation of China.