Date of Award


Document Type


Degree Name

Master of Arts (MA)



First Advisor

Kenneth A. Deffenbacher

Second Advisor

C. Raymond Millimet

Third Advisor

Edward LaCrosse


This study measured the extent to which the following four groups of Ss experienced the Mueller-L yer illusion: a group of ten congenital blind, ten Ss blinded in adulthood, ten sighted blindfolded Ss presented the illusion haptically, and ten sighted Ss presented the illusion visually. All of the groups experienced the illusion to a significant extent. The extent of illusion in the sighted haptic group was significantly less than that in each of the other groups, p < . 025 in each case. None of the other pairs of means w ere significantly different. Thus the results show that the blind do experience the Mueller-Lyer illusion similarly to the sighted, but the extent of illusion is much less for the sighted blindfolded. A positional memory hypothesis was presented to account for these results. It proposes that the blind have learned to remember the haptic location of objects in their environment but that the sighted have not developed this skill to the same degree.


A Thesis Presented to the Department of Psychology and the Faculty of the Graduate College University of Nebraska at Omaha In Partial Fulfillment of the Requirements for the Degree M aster of Arts.

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