Perceived causality can alter the perceived trajectory of apparent motion

When objects collide, human observers perceive not only motion but also causal relations, such as which object caused the other to move. In the present experiments, we investigated whether such causal interpretations can actually influence the perceived path of apparent motion. Displays contained two alternately flashing motion targets positioned at either end of a semicircular occluder. Two additional "context objects" moved in such a way that the motion targets appeared to collide with and launch them. The collision was manipulated so that it was consistent with apparent motion either along the straight path between the targets or along a curved path passing behind the occluder. Subjects almost exclusively perceived motion consistent with the implied launch, which suggests that causally coherent interpretations can influence basic perceptual processes.