Correlates of parallel wall detection for blinded veterans

Abstract

A two-alternative forced-choice methodology was designed to assess the ability of subjects to determine in a nonvisual manner the presence of a wall on their right side. Blindfolded subjects, beginning at a variable starting point, were led down a straight corridor and were either stopped at a point with walls on both sides (“closed” condition) or at a point with an intersecting corridor at their right side (“open” condition). The subject was asked to respond “open” or “closed” and was then led back to the starting area. This procedure was repeated for 50 trials and P.C. scores were determined for 22 blinded veterans and 16 sighted high school students. P. C. scores ranged from 0.38 to 0.98, with the mean falling at 0.64. Physical acoustic analysis of the ambient noise present in the opened and closed situations through the use of an artificial head recording technique revealed differential intensity information present below 2 kHz, with no signals recordable above 4 kHz. Results from the psychophysical procedure were examined for correlation with pure-tone audiometric data, age, personality factors as measured by C. P. I. and M. M. P. I. scales, verbal IQ, and the degree of visual impairment. Training methodologies as well as implications for the older blind are discussed.