Experience with morphosyntactic paradigms allows toddlers to tacitly anticipate overregularized verb forms months before they produce them

When do children acquire abstract grammatical categories? Studies of 2- to 3-year-olds' productions of complete morphosyntactic paradigms (e.g., all legal determiners with all nouns) suggest relatively later category acquisition, while studies of infant discrimination of grammatical vs. ungrammatical sequences suggest earlier acquisition. However, few of the latter studies have probed category generalization by examining how learners treat gaps in their input, and none have found evidence that learners before the age of 2 years fill gaps in VERB paradigms. Therefore, the three experiments presented here asked whether 16-month-olds tacitly expect to hear forms like breaked by presenting them with overregularized verbs vs. (1) nonce verbs + –ed, (2) real English nouns + –ed, and (3) the correct irregular counterparts. The pattern of listening preferences suggests that toddlers anticipate overregularized forms, suggesting that they have a general proto-category VERB, to which they expect the complete set of verb inflections to apply.