Mental rotation by the blind: does mental rotation depend on visual imagery?
Congentially blind adventitiously blind, and blindfolded sighted adults made same-different judgments of pairs of tactile forms. Two forms were presented in the same orientation, or one form differed from the other by a clockwise rotation of 30 degrees, 60 degrees, 120 degrees, or 150 degrees. Like the reaction times for the sighted and the adventitiously blind, reaction times for the congenitally blind increased as a linear function of angular discrepancy between stimuli, suggesting that the congentially blind, like the sighted and adventitiously blind, mentally rotated one form into congruence with the other to make judging easier. Corroboration of the mental rotation inference came from subjects’ introspective reports. Inasmuch as the congenitally blind presumably do not have the ability to visually represent form, the present results suggest that mental rotation does not depend upon visual imagery. Thus, with respect to current speculation as to whether visual imagery is a necessary component of mental rotation, the present findings suggest that it is not.