Early evidence for syntactic bootstrapping: 15-month-olds use sentence structure in verb learning

Infant language-learners receive input consisting of word sequences paired with world scenes. Based on these data, they start learning to understand sentences early in the second year, and ultimately build a lexicon and grammar that support broad generalization. Accounts of how they do so necessarily begin with the extra-linguistic world: The true novice, not yet knowing the words or syntax, must try to link input sentences with aspects of accompanying scenes. Top-down knowledge derived from the scene then ‘supervises’ word and syntax learning, investing words and their combinations with meaning. Views of language acquisition of all theoretical stamps thus assume that knowledge of word and sentence meaning drives syntax acquisition (e.g., Pinker, 1984; Tomasello, 2003). However, aspects of verb meanings in particular challenge the assumption that children can recover word and sentence meanings based only on understanding scenes, and thus in turn challenge our theories of syntax acquisition (Gleitman et al., 2005). Verbs do not simply label events; rather, they denote abstract construals of them. To illustrate, pairs of verbs such as feed and eat, give and receive, take different perspectives on the same events. Scene feedback thus provides equivocal evidence for verb and sentence meaning (Gillette et al., 1999). The syntactic-bootstrapping theory proposes that children use knowledge of syntax itself to decode sentence and verb meanings (e.g., Gleitman et al., 2005). Syntactic bootstrapping relies on tight links between verb syntax and meaning (Fisher et al., 1991; Levin & Rappaport-Hovav, 2005; Pinker, 1989). Part of the meaning of a verb is a semantic predicate-argument structure specifying the number and type of arguments that the verb’s meaning implies. This semantic structure partly determines the syntactic structures licensed by the verb. For example, verbs entailing one argument take intransitive frames, with one noun phrase (NP) (It fell); verbs entailing two arguments take transitive frames, with two NPs (I dropped it). Toddlers use these links, assigning different meanings to verbs in different syntactic structures (Arunachalam & Waxman, 2010; Fisher, 1996; Naigles, 1990, 1996; Yuan & Fisher, 2009; Yuan et al., 2012).