Similarity in linguistic categorization: The importance of necessary properties

Usage-based models of language propose that the acceptability of an element in a constructional slot is determined by its similarity to attested fillers of that slot (Bybee 2010, ch. 4). However, Ambridge and Goldberg (2008) find that the acceptability of a long-distance-dependency (LDD) question does not correlate with the judged similarity of the matrix verb to think and say, which are by far the most frequently attested fillers of this slot. They propose instead that the acceptability of LDD questions is determined by the degree of fit between the information-structure properties of the matrix verb and those specified by the construction—specifically, the degree to which the matrix verb foregrounds its complement clause. This paper explores the possibility of reconciling this explanation with one based on similarity by suggesting that in this case the relevant aspect of similarity is precisely the verb’s foregrounding of its complement. Evidence for this suggestion comes from psychological research showing that in a categorization task, the similarity of an item to the exemplars of a category is judged primarily with respect to the features common to all category members, as well as from the observation that virtually all attested matrix verbs in LDD questions strongly tend to foreground their complements.