Grammatical dependencies shape compositional units in sentence production.

Five recall-based structural priming experiments tested the predictions about dative structural priming derived from a new theory of structure building in sentence production. When both prime and target sentences contained direct object filler-gap dependencies, repeating a dative verb enhanced dative priming (the lexical boost). In contrast, the lexical boost was not observed when only target sentences contained object filler-gap dependencies. Additionally, the lexical boost was not observed when prime and target sentences contained object filler-gap dependencies but had mismatching tenses/aspects. In contrast, when neither prime nor target sentences contained object filler-gap dependencies, the lexical boost was observed despite prime and target sentences having different tenses/aspects. These findings confirm the unique set of predictions of the proposed theory, which posits that the size of compositional units is affected by the dependency structures of sentences.