THE GOLF-BALL ILLUSION - EVIDENCE FOR TOP-DOWN PROCESSING IN WEIGHT PERCEPTION

Theories of weight illusions have traditionally emphasised either the primary contribution of low-level sensory cues or the role of expectat ion based on knowledge and past experience. Current models of weight i llusions lean quite strongly towards sensory-based interpretations. Th e current experiment raises a problem for such approaches by generatin g a weight illusion that is difficult to explain other than by the par ticipants' knowledge. Golfers (who expect a weight difference between ball types) reliably judged practice golf balls to weigh more than rea l golf balls of the same weight. In contrast, non-golfers (who expect no weight difference between ball types) judged practice and real ball s of equal weight to weigh the same. Furthermore, within the group of golfers, those who expected the weights of the two ball types to be th e most discrepant prior to lifting tended to report the strongest illu sions subsequent to lifting. Because there is no low-level sensory cue between ball types that on its own would signal a weight difference, the current finding suggests that there is a top-down component to wei ght perception that is based on experience with specific objects.