Function words constrain on-line recognition of nouns and verbs in French 18-month-olds

In this experiment using the conditioned head-turn procedure, 18-month-old French-learning toddlers were trained to respond to either a target noun (“la balle”/<i>the ball</i>) or a target verb (“je mange”/<i>I eat</i>). They were then tested on target word recognition in two syntactic contexts: the target word was preceded either by a correct function word (“une balle”/<i>a ball</i> or “on mange”/<i>they eat</i>), or by an incorrect function word, signaling a word from the other category (*“on balle”/<i>they ball</i> or *“une mange”/<i>a eat</i>). We showed that 18-month-olds exploit the syntactic context on-line to recognize the target word: verbs were recognized when preceded by a personal pronoun but not when preceded by a determiner and vice-versa for nouns. These results suggest that 18-month-olds already know noun and verb contexts. As a result, they might be able to exploit them to categorize unknown words and constrain their possible meaning (nouns typically refer to objects whereas verbs typically refer to actions).