Postdiction refers to the phenomenon whereby the visual system retrospectively integrates information arriving within a brief (approximately 100–200 ms) window after an event to finalize perceptual judgements. We investigated whether observed action cues, specifically mouse-control movements by others that were causally irrelevant to the display, can influence this late integration. In the stream/bounce experiments, participants viewed two identical bars approach, spatially overlap, and separate. Another person (an experimenter) facing the participant operated a mouse mounted on a motorized slider that was causally irrelevant to the bars. The slider executed one of five movement patterns: no movement (control), non-invert (continuous movement in one direction), pre (reversal 150 ms before the bars overlap), at (reversal as the bars overlap), and post (reversal 150 ms after the bars overlap). The participants knew that the other person’s mouse movement could not influence the bars’ motion. Relative to the control condition, the other person’s mouse-control reversal movements increased “bounce,” whereas continuous noninverting movement decreased bounce. Critically, in the post condition, where the other person’s reversal followed the bars overlapping, bounce increased substantially, indicating a postdictive influence. These results show that another person’s movement can serve as a context-conditioned prior that is postdictively integrated to disambiguate motion correspondence.
Nomura et al. (Thu,) studied this question.