How Do Children Restrict Their Linguistic Generalizations? An (Un‐)Grammaticality Judgment Study

A paradox at the heart of language acquisition research is that, to achieve adult‐like competence, children must acquire the ability to generalize verbs into non‐attested structures, while avoiding utterances that are deemed ungrammatical by native speakers. For example, children must learn that, to denote the reversal of an action, un‐ can be added to many verbs, but not all (e.g., roll/unroll; close/*unclose ). This study compared theoretical accounts of how this is done. Children aged 5–6 ( N  =   18), 9–10 ( N  =   18), and adults ( N  =   18) rated the acceptability of un‐ prefixed forms of 48 verbs (and, as a control, bare forms). Across verbs, a negative correlation was observed between the acceptability of ungrammatical un‐ prefixed forms (e.g., *unclose ) and the frequency of (a) the bare form and (b) alternative forms (e.g., open ), supporting the entrenchment and pre‐emption hypotheses, respectively. Independent ratings of the extent to which verbs instantiate the semantic properties characteristic of a hypothesized semantic cryptotype for un‐ prefixation were a significant positive predictor of acceptability, for all age groups. The relative importance of each factor differed for attested and unattested un‐ forms and also varied with age. The findings are interpreted in the context of a new hybrid account designed to incorporate the three factors of entrenchment, pre‐emption, and verb semantics.