The role of working memory in structure prediction during language comprehension: Evidence from visual-world structural priming paradigm

Comprehenders can not only predict syntactic information of an upcoming word, but also of a larger unit, such as sentence structure. It is unclear whether such prediction effects are driven by an automatic processing or constrained by cognitive resources (e.g., working memory) in comprehension. In order to investigate the mechanism of structure prediction in comprehension (automatic vs. resource-constrained), we constructed two eye-tracking experiments to test the role of working memory (i.e., a number series recall task between prime and target exerting high or low working memory load) in structural priming during visual-world comprehension. The priming effect is evaluated by the proportion of looks to predicted referents for two critical time windows in target sentence processing: the target verb and the first syllable of the first postverbal noun. When prime and target involved different verbs (Experiment 1), structural priming in both time windows was similar between high and low load conditions. When prime and target involved same verbs (Experiment 2), structural priming in the time window of the first syllable of the first noun phrase was weaker in high load than in low load condition. Overall, structure prediction in comprehension is partially automatic, while the lexically-mediated structure prediction effect is modulated by working memory, supporting the implicit learning theory.