The haptic Müller-Lyer illusion in sighted and blind people.
We examined the effect of visual experience on the haptic Müller-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 Müller-Lyer illusion does not depend upon visual imagery or visual experience.
Heller
Morton A
MA
Department of Psychology, Eastern Illinois University, Charleston 61920, USA. cfmah1@eiu.edu
Brackett
Deneen D
DD
Wilson
Kathy
K
Yoneyama
Keiko
K
Boyer
Amanda
A
Steffen
Heather
H
D000328:Adult; D000704:Analysis of Variance; D001766:Blindness / Q000523:psychology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011601:Psychophysics; D012858:Size Perception / Q000502:physiology; D013236:Stereognosis / Q000502:physiology*; D015354:Vision, Low / Q000503:physiopathology / Q000523:psychology