Mental Rotation and Visual Imagery

Describes a study designed to test differences in how the two hemispheres of the brain handle spatial information. Congenitally blind, adventitiously blinded, and blindfolded sighted subjects tactually examined a target shape and selected its duplicate from three shapes placed in different orientations relative to the target. The performances of all groups declined as the relative disorientation between the target and its duplicate increased, suggesting that visual imagery is not crucial to mental rotation. In addition, the sighted subjects performed better with the left hand than did the blind subjects. Because braille is usually read with both hands, this difference was surprising. The author speculates that the sighted subjects were able to recode the tactual information into both the verbal and visual modes whereas the blind subjects relied on the left hemisphere's verbal strategy only.