Cross-linguistic similarities and differences in early lexical
and grammatical
development are reported for 1001 English-speaking children
and 386 Italian-speaking children between 1;6 and 2;6. Parents completed
the English or Italian versions of the MacArthur Communicative
Development Inventory: Words and Sentences, a parent report instrument
that provides information about vocabulary size, vocabulary
composition and grammatical complexity across this age range. The
onset and subsequent growth of nouns, predicates, function words and
social terms proved to be quite similar in both languages. No support
was found for the prediction that verbs would emerge earlier in Italian,
although Italians did produce a higher proportion of social terms, and
there were small but intriguing differences in the shape of the growth
curve for grammatical function words. A strikingly similar nonlinear
relationship between grammatical complexity and vocabulary size was
observed in both languages, and examination of the order in which
function words are acquired also yielded more similarities than differences.
However, a comparison of the longest sentences reported for a
subset of children demonstrates large cross-linguistic differences in the
amount of morphology that has been acquired in children matched for
vocabulary size. Discussion revolves around the interplay between
language-specific variations in the input to young children, and universal
cognitive and social constraints on language development.