Constructions as categories of language

What causes children to categorize distinct utterances they hear into a constructional generalization? That is, what makes subjects create a constructional category instead of treating each utterance as a distinct unrelated idiom? One simple factor that encourages the learning of abstract categories is shared concrete similarity. When instances share concrete attributes, learners are more likely to categorize them together, and moreover are more likely to attend to their abstract commonalities [Gentner, D., & Medina, J. (1998). Similarity and the development rules. Cognition, 66, 236-297; Markman, A.B., & Gentner D. (1993). Splitting the difference: A structural alignment view of similarity. Journal of Memory and Language, 32, 517-535]. This paper reports results that confirm the prediction that presentation of items with concrete shared similarity early in training enhances language learning in adults.