It is well known that human skin is a viscoelastic material, and the mechanical and electrophysiological responses to transient indentation have been studied and modelled. For tactile display system design, it is also important to determine the perceptual effects, if any, of skin viscoelasticity. The spatial characteristics and sinusoidal steady state response of the sense of touch have been comparatively well studied. This paper describes initial work in quantifying tactile “after-images” resulting from large loads applied over several seconds to the finger tip. We first measured finger tip relaxation responses. We then ran psychophysical experiments on human subjects to determine if viscoelastic memory affects tactile perception. To reduce sensitivity to fine surface detail and since most teletaction systems will include an elastic layer as an anti-aliasing filter, our tests were carried out with a layer of elastic material on the finger. We found a statistically significant correlation between mechanical memory and perception “after-images” from large loads presented to the subjects. We offer a possible explanation for the results based on simplified mechanical models of the skin.

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