The effect of birth order on the occurrence of developmental language impairment

The birth order of second-grade children with and without developmental language impairment was obtained to determine if language-impaired children were more likely to be later born than earlier born. In this study the family size and socioeconomic status of the families for the language-impaired and normal groups were very similar. Comparison of the distribution of birth ranks between second-grade language-impaired and normal second-grade children failed to show a difference in birth ranks. Further, the distribution of birth ranks of all language-impaired children within the sibships was not found to show evidence favouring either early or later born birth ranks. Thus, contrary to previous research in which family size and socioeconomic status were not controlled, this study did not provide evidence in support of a birth order effect in developmental language impairment.