Laterality and the Growth of Intellectual Abilities

S ummary . A random sample of right‐handed children and a population sample of left‐handed children, including over 100 subjects in each group, were assessed for vocabulary, drawing, maze tracing and for laterality of hand, eye and foot. Reading quotients were available for 145 children. The data were examined in two ways. The first compared the abilities of laterality groups over the total sample and found no significant differences. The second assessed the laterality of children at the lower extreme of the ability distribution and found a slight excess of left handers. A brief survey of the literature shows that a distinction between studies according to their resemblance to these two analyses could help to account for the coexistence of positive and negative findings. Possible causes of the excess of children with sinistral tendencies in groups selected for educational disabilities are discussed with special reference to a theory of the determination of handedness (Annett, 1972) which permits a restatement of the maturational lag hypothesis of developmental language delay.