Enhanced Roughness-Matching Precision for Random Grating Textures at a 1.0-mm Mean Wavelength

Natural surfaces contain local spatial irregularities, yet tactile texture perception has often been characterized in terms of mean geometric properties. It remains unclear whether information associated with such irregularities improves roughness-matching precision when the mean spatial scale of a texture is varied. We compared roughness-matching precision between physically fabricated periodic and random gratings with nominal mean wavelengths of 1.0 and 2.0 mm. Participants selected, from a set of test gratings, the stimulus whose roughness they perceived as closest to that of a reference. Matching precision was quantified for each participant and condition using the standard deviation of the nominal wavelengths selected across repeated trials, with a smaller standard deviation indicating more precise roughness matching. At the nominal mean wavelength of 1.0 mm, the standard deviation was significantly smaller for the random gratings than for the periodic gratings. No significant difference was observed at 2.0 mm. These findings suggest that information contained in the 1.0-mm random gratings beyond their mean wavelength may have contributed to roughness matching precision.