Causality modulates perception of apparent motion stimuli

Previous studies have shown that contextual information can alter judgments of apparent motion. Specifically, the presence of causal information can even override the shortest-path bias, if the shortest path is inconsistent with a causal interpretation of the motion event. While these results demonstrate that judgments of apparent motion are affected by causality, how causality modulates lower-level spatiotemporal processing is not yet understood. Moreover, it is unclear whether subjects' judgments of apparent motion are the result of perceptual processing or higher-level reasoning. Addressing these questions, we investigated whether causal information could influence detection sensitivity in an apparent motion display. Our apparent motion displays involved two vertically stacked semicircular tubes, and contextual information suggested either motion through the top or bottom tube. Each tube contained a small aperture that would flash, appearing as if the launched object was briefly visible along the motion-path. In addition, contextual information could also be inconsistent with the flash location. In our first experiment, participants judged the location of the target flash under causal and noncausal conditions. In experiment 2, we compared the effect of causality with motion priming, a noncausal cue that may covary with the causal cue. In both experiments, detection was most influenced by causal information, being most accurate when causality was consistent with the target flash and least accurate when causal information acted as a distractor- suggesting that the visual system generates spatiotemporal predictions of object motion during perceived causal interactions.