Haptic metameric textures

Humans sense spatial patterns through their eyes and hands. Past studies have revealed differences (as well as similarities) between vison and touch in texture processing (e.g., eye is good at detecting texture boundaries, while hand can discriminate subtle texture differences), but the underlying computational differences remains poorly understood. Here we transcribed various textures as surface relief patterns by 3D-printing, and analyzed the tactile discrimination performance regarding the sensitivity to image statistics. The results suggest that touch is sensitive to texture differences in lower-order statistics (e.g., statistics of local amplitude spectrum), while may not to those in the higher-order statistics (e.g., joint statistics of local orientations). In agreement with this, we found that pairs of synthesized textures differing only in higher-order statistics were nearly indiscriminable (metameric) by touch, while easily discriminable by vision. Our findings show that touch and vision sense spatial information using different and complementary computational strategies.