Hapto-visual Virtual Reality as a Tool in Psychophysical Research on Roughness Sensitivity

In this study, we present a method for psychophysical measurements of surface roughness sensitivity by indirect touch, using a 3D hapto-visual virtual reality (VR) device. In a texture-difference-recognition test subjects glided a pen-like stylus on a virtual surface. The surface was divided into five areas: one central, and four surrounding areas. The roughness of the central area was kept constant throughout the experiment. In each run, three of the four surrounding areas were kept at the same roughness as the central surface, and one, randomly, was different. From run to run, surface roughness was changed following a binary search paradigm. If a subject recognized the portion of the surface with a different roughness, then the roughness was reduced by half; if not, the roughness increased, and so on, until the desired number of steps was achieved. This approach allows us to take advantage of the programmable capabilities of a VR, so that the limit of aware recognition between surfaces with different roughness can be measured with more precision than in conventional methods. To illustrate this paradigm, results from a preliminary study are presented.