Haptic integration of planar size with hardness, texture, and planar contour

Three studies investigate the role of size information in haptic classification of custom-made planar objects when size covaries with hardness, texture, or planar contour. The haptic exploratory procedure (Lederman & Klatzky, 1987) associated with size extraction is also sufficient for encoding shape, which should promote their integration. Experiment 1 showed substantial facilitation of classification by redundant size and shape cues, indicating the coprocessing of size and shape. Experiments 2 and 3 used a withdrawal paradigm: Classification trials began with two redundant properties, and one was then held constant (withdrawn). Experiment 2 showed that when size and shape were redundant, withdrawal of either impaired responses, whereas when size was redundant with texture or hardness, only size withdrawal had an effect. Experiment 3 demonstrated that this size weighting was not restricted to a single procedure for exploration. Size appears to be highly weighted in haptic classification and potentially integrated with other properties having compatible methods of extraction.