Specific language impairment as a maturational lag: evidence from longitudinal data on language and motor development.

Longitudinal language-test data on 87 language-impaired children assessed at the ages of four, 4 1/2 and 5 1/2 years were converted to age-equivalent scores to compare the rates of development of children who recover from early language delay with those who have more persisting problems. On most measures, over the 18-month period all the children progressed by about 18 months. Thus although children with good and poor outcomes were distinguished in terms of initial level of performance, they did not differ in rate of progress. Speed on a peg-moving task was closely related to language performance. Children who had a good outcome after early language delay had significantly impaired scores at four years, but subsequently were indistinguishable from a control group. Quantitative but not qualitative differences in peg-moving performance were found for children with good and poor outcomes. No association was found between presumptive aetiological factors and language or pegboard performance. These findings are interpreted in terms of a theory which attributes specific language impairment to a maturational lag in neurological development.