Tactile roughness perception with a rigid link interposed between skin andsurface

Subjects made roughness judgments of textured surfaces made of raised eleme nts, while holding stick-like probes or through a rigid sheath mounted on t he fingertip. These rigid links, which impose vibratory coding of roughness , were compared with the finger (bare or covered with a compliant glove), u sing magnitude-estimation and roughness differentiation tasks. All end effe cters led to an increasing function relating subjective roughness magnitude to surface interelement spacing, and all produced above-chance roughness d iscrimination. Although discrimination was best with the finger, rigid link s produced greater perceived roughness for the smoothest stimuli. A peak in the magnitude-estimation functions for the small probe and a transition fr om calling more sparsely spaced surfaces rougher to calling them smoother w ere predictable from the size of the contact area. The results indicate the potential viability of vibratory coding of roughness through a rigid link and have implications for teleoperation and virtual-reality systems.