Strategic hand use preferences and hemispheric specialization in tactual reading: impact of the demands of perceptual encoding

Four reading-related, information-processing tasks were administered to right-handed blind readers of braille who differed in level of reading skill and in preference for using the right hand or the left hand when required to read text with just one hand. The tasks were letter identification, same-different matching of letters that differed in tactual similarity, short-term memory for lists of words that varied in tactual and phonological similarity, and paragraph reading with and without a concurrent memory load of digits. The results showed interactions between hand preference and the hand that was actually used to read the stimulus materials, such that left preferrers were significantly faster and more accurate with their left hands than with their right hands whereas right preferrers were slightly but usually not significantly faster with their right hands than with their left hands. In all cases, the absolute magnitude of the left-hand advantage among left preferrers was substantially larger than the right-hand advantage among right preferrers. The results suggest that encoding strategies for dealing with braille are reflected in hand preference and that such strategies operate to modify an underlying but somewhat plastic superiority of the right hemisphere for dealing with the perceptual requirements of tactual reading. These requirements are not the same as those of visual reading, leading to some differences in patterns of hemispheric specialization between readers of braille and readers of print.