Abstract
The aim of the present investigation was to demonstrate the relaton between the development of hand preference and langage development. The subjects were 50 severely retarded children with MAs of 3 or below. CAs ranged from 7 to 17. A hand preference test and a language development test for infants were given individually. The hand preference test consisted of seven tasks (handing over a block, switching something on, pointing, drawing a circle, beating a drum, throwing a ball, eating a chocolate). On each task experimental objects were presented on the right, middle, and left side in front of subjects. All seven tasks were scored for the hand used. This scoring reflects the extent of laterality (the frequency of right-handed responses) and handedness (dextrality, sinistrality, mixed, and indistinguishable type). Dextral handers were those consistent in using the right hand for any or all tasks, sinistral handers were those consistent in using the left hand for any or all tasks, mixed handers were those who showed any combination of preference, and indistinguishable handers were those who did not show any preference for all tasks. A language development test for infants was given out to the parents (or teachers) and requested to be handed in one week later. This test allowed for evaluation of language development on two measures (receptive and expressive scores). The results obtained were as follows: 1. The incidence of ambidexters (mixed plus indistinguishable type) did not show any change with MA or language measures. 2. There were no differences between dextral handers and non-dextral handers in the language measures. 3. A significant relation between the extent of laterality and language measures was demonstrated for dextral handers with an MA of 3, but not for dextral handers with an MA below 3. The implications of the results were discussed in terms of the ontogenesis of hemispheric specialization for language. The results did not corroborate the traditional hypothesis of progressive language lateralization.
