A comparison of visual and two modes of tactual letter resolution

Abstract

Confusion matrices were obtained for visual letter recognition and for tactual letter recognition with (1) the finger held stationary on small raised letters and (2) the finger allowed to scan them. In each sensory mode, performance was investigated at four letter sizes, with heights ranging from 1.5 to 3.0 min of arc for vision and from 3.0 to 8.0 mm for touch. The two tactual modes yielded similar recognition performance, although performance was always better in the scanned mode. For both vision and touch, performance appeared to be limited by primary receptor spacing. Letter heights corresponding to 50% correct identification (vision, 2.2 rain arc; scanned touch, 4 ram; static touch, 5 ram) spanned about five receptor spacings in each sensory system, indicating that the dimensional equivalence of vision and touch is determined by receptor spacing rather than central factors. The patterns of letter confusions and the productmoment correlations for correct identifications (vision vs. static touch, 0.83; vision vs. scanned touch, 0.75; and static touch vs. scanned touch, 0.89, all taken at comparable performance levels) imply that similar spatial processes are involved in the different modes. © 1983 Psychonomic Society, Inc.