Structural priming in sentence comprehension: A single prime is enough

Experiencing a syntactic structure affects how we process subsequent instances of that structure. This phenomenon, called structural priming, is observed both in language production and in language comprehension. However, while abstract syntactic structures can be primed independent of lexical overlap in sentence production, evidence for structural priming in comprehension is more elusive. In addition, when structural priming in comprehension is found, it can often be accounted for in terms of participants' explicit expectations. Participants may use the structural repetition over several sentences and build expectations, which create a priming effect. Here, we use a new experimental paradigm to investigate structural priming in sentence comprehension independent of lexical overlap and of participants' expectations. We use an outcome dependent variable instead of commonly used online measures, which allows us to more directly compare these effects with those found in sentence production studies. We test priming effects in syntactically homogeneous and heterogeneous conditions on a sentence-picture matching task that forces participants to fully parse the sentences. We observe that, while participants learn the structural regularity in the homogeneous condition, structural priming is also found in the heterogeneous condition, in which participants do not expect any particular structure. In fact, we find that a single prime is enough to trigger priming. Our results indicate that-like in sentence production-structural priming can be observed in sentence comprehension without lexical repetition and independent of participants' expectation.