Contrastive patterns of intrahemispheric interference to verbal and spatial concurrent tasks in right-handed, left-handed and stuttering populations.

A time-sharing paradigm was used to assess hemispheric lateralization for both language and visuo-spatial processing in right-handed, left-handed and stuttering populations. A right hand only tapping disruption, indicative of left hemisphere interference, accompanied concurrent verbal tasks only in the dextral group. Left-handers and stutterers revealed symmetrical patterns of hemispheric language interference. Significantly different absolute levels of language interference were found for the three groups, with dextrals having the least, followed by sinistrals, and being greatest for stutterers. These magnitude differences were explained in relation to a hypothesis of strength of language representation within a given hemisphere. Visuo-spatial right hemisphere interference was shown for left-handers with a concurrent object chimera task.