We examined the effect of visual experience on the haptic Mu« ller-Lyer illusion. Subjects made size estimates of raised lines by using a sliding haptic ruler. Independent groups of blind- folded-sighted, late-blind, congenitally blind, and low-vision subjects judged the sizes of wings-in and wings-out stimuli, plain lines, and lines with short vertical ends. An illusion was found, since the wings-in stimuli were judged as shorter than the wings-out patterns and all of the other stimuli. Subjects generally underestimated the lengths of lines. In a second experiment we found a nonsignificant difference between length judgments of raised lines as opposed to smooth wooden dowels. The strength of the haptic illusion depends upon the angles of the wings, with a much stronger illusion for more acute angles. The effect of visual status was nonsignificant, suggesting that spatial distortion in the haptic Mu« ller-Lyer illusion does not depend upon visual imagery or visual experience.
Heller, Morton A.; Brackett, Deneen D.; Wilson, Kathy; Yoneyama, Keiko; Boyer, Amanda; and Steffen, Heather, "The haptic Muller-Lyer illusion in sighted and blind people" (2002). Faculty Research and Creative Activity. 8.