Mechanisms of fine-surface-texture discrimination in human tactile sensation

The purpose of this study was to evaluate the ability of touch to discrimin ate fine-surface textures and to suggest possible mechanisms of the discrim inations. Two experiments were performed. In experiment 1, aluminum-oxide a brasive papers were adopted as stimuli, and psychometric functions and diff erence thresholds were determined in fine-surface-texture discrimination ta sks. The grit values of abrasive papers were 400, 600, 1200, 2000, 3080, 40 00, and 8000; corresponding average particle sizes were 40, 30, 12, 9, 5, 3 , and 1 mu m, respectively. Ten subjects participated in experiment 1. The difference thresholds obtained in experiment 1 were between 2.4 and 3.3 mu m. In experiment 2, the tasks were discriminations of ridge height. The cro ss sections of the etched ridges were rectangular and the ridge heights wer e 6.3, 7.0, 8.6, 10.8, 12.3, 18.5, and 25.0 mu m. Six subjects participated in experiment 2. The difference thresholds in experiment 2 were between 0. 95 and 2.0 mu m. It was reasoned, based on the Weber fraction values calcul ated from the difference thresholds and on the limit of neural information- processing ability of humans, that the subjects discriminate fine roughness only from the amplitude information presented in surface unevenness, (C) 1 999 Acoustical Society of America. [S0001-4966(99)05903-2].