Language Acquisition

The ability to represent both local and nonlocalsyntactic dependencies emergesin an infant’ssecond year of life, raising questions about how these early syntactic representations interact with language learning in other domains. Using wh-questions as our case study, we investigate how infants’ syntactic dependency acquisition interacts with their early lexical development. Prior work finds that 18-month-olds represent fronted wh-phrases as nonlocal arguments in object wh-questions with known verbs. Here, we show that 19–21-month-olds (range: 18;29–21;26) do the same when interpreting unknown verbs. We introduce a novel Violation of Fit method, a cross-modal extension of the Violation of Expectations paradigm. Infants saw dialogues with novel verbs in object wh-questions (e.g., What is the girl gonna gorp?), transitive polar questions (Is the girl gonna gorp the toy?), or intransitive polar questions (Is the girl gonna gorp?). At test, infants viewed a causal event (e.g., a girl knocks over a tower), and we measured their attention as an indication of whether they considered the verbs to be a good fit for this type of event. Across the age range, we found that infants who heard wh-question dialogues attended similarly to the test events as infants who heard canonical transitive dialogues, and unlike infants who heard intransitive dialogues. Thus,19–21-month-oldstreat object wh-questions with a novel verb as transitive when relating them to scenes. This suggests that immediately after wh-dependency representations are first acquired, they are available to feed verb learning.

In acquiring a syntax, children must detect evidence for abstract structural dependencies that can be realized in variable ways in the surface forms of sentences. In What did David fix?, learners must identify a nonlocal relation between a fronted object of the verb (what) and the phonologically null ‘gap’ in canonical direct object position after the verb, where it is thematically interpreted. How do learners identify a nonadjacent dependency between an expression and something that has no overt phonological form? We propose that identifying abstract syntactic dependencies requires statistical inference over both overt linguistic material and unsatisfied grammatical expectations: noticing when a predicted argument for a verb is unexpectedly missing may serve as evidence for the gap of an argument movement dependency. We provide computational support for this hypothesis. We develop a learner that uses predicted but unexpectedly missing objects of verbs to identify possible gaps of object movement, and identifies which surface morphosyntactic properties of sentences are correlated with these possible movement gaps. We find that it is in principle possible for a learner using this mechanism to identify the majority of sentences with object movement in child-directed English, and that prior knowledge of which verbs require objects provides an important guide for identifying which surface distributions characterize object movement. This provides a computational account for why verb argument-structure knowledge developmentally precedes the acquisition of movement in a language like English. More broadly, these findings illustrate how statistical learning and learning from violated expectations can be combined to novel effect in the domain of language acquisition.

In syntactic bootstrapping, children draw on syntactic information to constrain their hypotheses about word meanings. We review evidence for syntactic bootstrapping, focusing primarily on the acquisition of verb meanings. For verbs describing physical actions, children can use the argument structure from event descriptions to zero in on the verb meaning. For attitude verbs, which refer to mental states, the syntactic distribution is informative about their semantics. By making use of systematic syntax-semantics correspondences, syntactic bootstrapping provides a foothold for word learning when cues from the physical world are underinformative.