THE EFFECT OF LOCATION ON THE DISCRIMINATION OF SPATIAL VIBROTACTILE PATTERNS

The present study examined whether the locations of patterns on the sk in affected the ability to process information about their shapes. In Experiment 1, pairs of spatial vibrotactile patterns, using the array from the Optacon, were presented sequentially to subjects' left index fingerpads. The location of each pattern in a pair was varied randomly among four locations on the skin. The subjects responded ''same'' or ''different'' on the basis of the shapes of patterns, regardless of th eir locations. Discrimination accuracy was highest and response time f astest when patterns occupied identical locations (ILs), and performan ce suffered with increasing distance between patterns. In Experiment 2 , pairs were presented to corresponding points or to noncorresponding points on separate fingerpads. When patterns occupied corresponding po ints on separate fingers, accuracy was lower than when patterns occupi ed ILs on a single finger, but higher than when patterns occupied nonc orresponding points on separate fingers. The results suggested that di scriminability declined partly because patterns did not occupy ILs, an d partly because separate locations had different densities of innerva tion.