COUNTEREXAMPLE TO THE HYPOTHESIS OF FUNCTIONAL SIMILARITY BETWEEN TACTILE AND VISUAL-PATTERN PERCEPTION

In earlier work, the author has demonstrated that tactile pattern perc eption and visual pattern perception exhibit many parallels when the e ffective spatial resolution of vision is reduced to that of touch, thu s supporting the hypothesis that the two pattern senses are functional ly similar when matched in spatial bandwidth. The present experiments demonstrate a clear counter-example to this hypothesis of functional s imilarity. Specifically, it was found that the lateral masking effect of a surround on tactile character recognition increases when the surr ound changes in composition from solid lines to dots, whereas for visi on, recognition performance goes in the opposite direction. This findi ng necessitates some modification of the model of character recognitio n proposed by the author (Loomis, 1990) as it applies to the sensing o f raised tactile patterns. One possible modification would be to incor porate, as the initial stage of pattern transformation, the continuum mechanics model for the skin that was developed by Phillips and Johnso n (1981b).