Preventive Medicine

This report is concerned with the sources of language a lack of systematic work on the possible effects of landevelopment in the child. We have found a substantial guage input on vocabulary size. Clearly, however, vocabrelation between naturally occurring variations in ulary has to be learned, and attaining a large vocabuchildren’s language environments and their language lary is a huge associative learning task. skills, both at the earliest stages of language developConsider syntactic skill among different individuals. ment and later, at 5 and 6 years of age. Our studies Syntactic development has been of central interest in show that children’s language development is related linguistic theory. It is claimed that, contrary to vocabuto the speech they hear at home and the speech they lary, there isn’t much variation among individuals in hear at school. Although much more work remains to syntactic skill. Since language, by which linguists mean be done, it is clear that differences in language input syntax, is a species-wide competence reflecting our hewithin the normal range are causally related to the reditary structure as humans, it is universal. Although growth of children’s vocabularies and their syntactic some input is required to “trigger” the innate syntactic skills. q1998 American Health Foundation and Academic Press device, only extreme deprivation should disrupt normal