Jimin Ju¹ (), Sung-ho Kim; ¹Ewha Womans University

Michottian studies on causal perception have primarily investigated spatiotemporal factors influencing causal relationship between two rigid bodies in billiard-ball-like collisions. Here, we present a novel bistable causal perception phenomenon involving a 'separation' event: A thick horizontal line rooted in a stationary rectangle elongates to the right, as a disc connected to its right end simultaneously moves to the right at an identical speed; halfway through this motion, the line and the disc separate; subsequently, the line returns to its initial length, while the disc continues moving to the right and then comes to a halt. This sequence could be perceived as either “a stick pushed a ball to move” or “a ball pulled a rubber band, stretching it until snapped.” In Experiments 1-3, we investigated how the causal interpretation of the line-disc relationship is disambiguated by their kinematic properties before and after the separation, using both free report and forced choice tasks. The results showed that the “pulling” interpretation was dominant over the “pushing” percept when their motion decelerated before separation and when they moved rapidly after separation. In Experiment 4, we employed an indirect, performance-based, pause-detection task, in which to detect whether line motion momentarily paused immediately after the separation. The results indicated higher sensitivity in detecting the pause when the objects’ pre-separation speed decreased (i.e., in the “a ball pulling a rubber band” percept-dominant condition), suggesting that the presence of the pause is incompatible with the perceived elasticity of the line returning to its relaxed state. This study demonstrates that subtle changes in low-level kinematic features alone can radically alter perceptions of the agent-patient relationship of moving objects and their material properties (elastic vs. rigid) simultaneously. It further suggests that the visual system is reliably tuned to the physical regularities of various dynamic-kinematic mappings beyond collision events.