Evidence for the representation of non-hierarchical structures in language

A long-standing assumption in the language sciences is that the mental representation of language is based on constituents-that is, hierarchical structures rooted in grammar. We provide evidence from English for a more basic kind of linguistic representation involving smaller, linear chunks of structure akin to sequences of parts-of-speech elements-such as VERB PREPOSITION DETERMINER shared between the strings added to a and defined by the. Across four preregistered phrasal decision experiments (total N = 497), we show that it is possible to prime such linear structures, even in the absence of constituents. In two additional corpus analyses of eye-tracked reading (N = 68) and conversation (N = 358), we establish the external validity of the effect. These results provide evidence of multiword language structures that are not explainable in terms of constituents as traditionally construed. This poses a challenge for accounts of linguistic representation, including generative and constructionist approaches.