Perceiving Roughness via a Rigid Probe: Psychophysical Effects of Exploration Speed and Mode of Touch

Two experiments investigated the psychophysical consequences for roughness perception of altering the speed of motion with which real textured surfaces are explored using a rigid probe. Two speed ranges were used: a 10-fold change (Experiment 1) and a 4-fold change (Experiment 2). Relative motion was altered both by moving the probe actively over a stationary surface (active mode) and by moving the surfaces under the stationary probe (passive mode). Substantial effects of speed were obtained relative to previous studies. The results are examined both in terms of the complex effects of speed on the psychophysical roughness functions and in terms of an increase in the size of the maximum speed effect as the range of speeds explored was reduced. We also consider how best to minimize potentially negative effects of speed on the haptic exploration of simulated textures. Two operatortraining procedures are proposed to achieve effective haptic exploration strategies.