Later rather than sooner: extralinguistic categories in the acquisition of Thai classifiers.

An experimental elicitation task with children between the ages of 1;8 and 11;3 shows that children learning Thai numerical classifiers begin with purely distributional information: specifically, (1) that classifiers must appear in the post-numeral position, and (2) that classifiers comprise a conventional, closed set of words. Semantic organizing features, such as salient features of the head noun's referent, appear later than these syntagmatic organizing features. Use of such semantic information is not an immature 'first guess' at grammatical categories, but rather, a necessary component of adult linguistic competence, because the categories are productive both for older children and for adults.