Modes of vibrotactile pattern generation.

Two modes of generating vibrotactile patterns, static and scanned, were examined. In the static mode, all elements making up the pattern were turned on and off simultaneously. In the scanned mode, the pattern to be identified was moved across the tactile array. The patterns were letters of the alphabet presented to the fingertips by means of the Optacon, a reading aid for the blind. The results of the first experiment showed that the performance on a letter recognition task decreased as pattern duration decreased and that at all durations below 200-msec performance in the static mode was better than in the scanned mode. Good letter recognition was possible at durations of 4 msec in the static mode. The results of the second experiment showed that letter recognition in the static mode was highly dependent on the perceived intensity of the letters presented, whereas intensity changes in the scanned mode had little effect on letter recognition. The results of the third experiment showed that both modes of pattern presentation produced similar results in the presence of masking stimuli. The implications of the results for cutaneous pattern perception and information transmission and visual letter recognition are discussed.