DOES PERCEIVED SIZE DEPEND ON PERCEIVED DISTANCE - AN ARGUMENT FROM EXTENDED HAPTIC PERCEPTION

Two experiments were directed at the comparison between two perspectiv es on the perception of size achieved by probing the gap between two o ccluded distal surfaces by means of a hand-held rod. One perspective w as the classical size-distance invariance hypothesis developed for the problem of visual size perception with a central role for perceived d istance; the other was the hypothesis that the extended haptic percept ion of gap size is specific to a physical invariant lambda of the dyna mics of probing. Experiment 1 examined the relation between haptically perceived gap size and haptically perceived gap distance. No causal c onnection between the two was found, and all the variance in perceived size was accounted for by lambda. Experiment 2 manipulated the rotati onal inertia of the probe. Its effect was different for the two percep tions of size and distance, underscoring their independence. The indif ference of perceived size to perceived distance was discussed in refer ence to identifying invariants for both the haptic and the visual perc eption of size at a distance.