“Really, he dased the doll to the girl?” Two-year-olds can exploit grammatical and thematic content to learn novel verb meanings

Infants exploit the syntactic context verbs appear in to guide verb learning: a mechanism known as syntactic bootstrapping. However, it remains unclear whether infants' bootstrapping representations are achieved by matching the number of nouns in a sentence to the number of participants in an event, or by exploiting a more specific mapping between syntactic positions and thematic roles. To investigate this, we tested toddlers' ability to learn the meaning of a novel verb by relying on sentences' grammatical and thematic content, signaled by functional words connecting two noun phrases. French-learning 30-month-olds (n = 38) heard dialogues introducing a novel verb in either ditransitive sentences ('Le garçon va daser la poupée à la fille' - 'The boy will dase the doll to the girl') or conjoined-object transitive sentences ('Le garçon va daser la poupée et la fille' - 'The boy will dase the doll and the girl'). Toddlers were then asked to look for 'daser' while watching two different events, containing three characters each: one depicted a transfer action, the other a causative action. Results showed that toddlers who heard the novel verb in ditransitive sentences looked more to the transfer event than those who heard conjoined-object transitive sentences. As both types of sentences contained three noun phrases, success in our task suggests that toddlers can go beyond the strategy of matching the number of noun phrases in a sentence to participants in an event. Therefore, the current study provides clear evidence that already at 30 months, grammatical and thematic content can guide verb learning.