ANISOTROPY IN HAPTIC CURVATURE AND SHAPE PERCEPTION

An investigation was undertaken into whether haptic comparison of curv ature and of shape is influenced by the length/width ratio of the hand . For this purpose three experiments were conducted to test the curvat ure matching of curved strips (experiment 1), the curvature matching o f cylindrically curved hand-sized surfaces (experiment 2), and the sha pe discrimination of elliptically curved hand-sized surfaces (experime nt 3). The orientation of the stimuli with respect to the fingers was varied. The results of the two matching experiments showed that a give n curvature is judged to be more curved when touched along the fingers than when touched across the fingers. The phenomenal flatness along a nd across the fingers was found to be different and subject dependent. The results of the shape-discrimination experiment showed that the or ientation of ellipsoidal surfaces influences the judgments of the shap es of these surfaces. This influence could be predicted on the basis o f results of the second matching experiment. It is concluded that simi lar mechanisms underlie the (anisotropic) perception of curvature and shape. For the major part the trends in the results can be explained b y the length/width ratio of the hand and the phenomenal flatnesses.