Types of dyslexia and the shift to dextrality.

The prediction of the right shift theory that there are two types of dyslexia with different distributions of handedness was examined in a large cohort of school children. Dyslexics with poor phonology were less biased to dextrality than controls, while dyslexics without poor phonology tended to be more dextral than controls on measures of hand preference and hand skill. Relatives also differed for handedness, as expected if phonological dyslexics were less likely than nonphonological dyslexics and controls to carry the hypothesized rs + gene.