Crying helps, but being sad doesn't: Infants constrain nominal reference online using known verbs, but not known adjectives

Speakers can make inferences about the meaning of new words appearing in an utterance based on the lexical semantics of other words that co-occur with them. Previous work has revealed that infants at 19 and 24 months of age can recruit the semantic selectional restrictions of known verbs (e.g., eating) to deduce that a noun appearing in the subject position maps onto an animate referent. We asked whether this ability to capitalize on the semantics of familiar words to identify the referent of a novel noun in subject position extends to adjectives, which also denote properties, and which also have animacy constraints (e.g., hungry). We found that unlike in the previous studies with verbs, neither 24- nor 36-month-olds could successfully recruit known adjectival semantics in an online task to home in on an animate nominal referent. However, 36-month-olds were successful in a more interactive, forced-choice version of the task without such strict time limitations. We discuss multiple non-mutually-exclusive hypotheses for this pattern of results, focusing on the role of the morphosyntactic cues, the (lack of) perceptual cues for the target property in context of the utterance, truth conditions, and cross-linguistic implications. These possibilities raise fundamental questions about the infant's developing lexicon and the linguistic and conceptual mechanisms at play in the process of word learning.