Is the left hemisphere specialized for language at birth?

Abstract The recognition of the lateralization of language to the left hemisphere in most adults was one of the great triumphs of nineteenth-century neurology, but because the clinical finding of frequent crossed aphasia in children suggested that language functions were bilateral during childhood, the notion arose that lateralization was a developmental process that occurred over the first decade of life. Recent neuroanatomical, electroencephalographic and neuropsychological investigations have tended to support the contrary view that language is primarily lateralized to the left hemisphere from the first months of post-uterine life. Now the collection of more clinical data on acquired childhood aphasia, and the reanalysis of earlier clinical studies, indicate that the modern incidence of crossed aphasia in children is too low to support the hypothesis of a gradual lateralization of language over time, and is more consistent with a theory of developmental invariance of language lateralization.