Predictive structure building in language comprehension: a large sample study on incremental licensing and parallelism.

In online language comprehension, the parser incrementally builds hierarchical syntactic structures. The predictive nature of this structure-building process has been the subject of extensive debate. A previous study observed that when a wh-phrase indicates parallelism between the upcoming wh-clause and a preceding clause (e.g., John told some stories, but we couldn't remember which stories…), the parser predictively constructs the wh-clause. This observation demonstrates predictive structure building. However, the study also suggests that the parser does not make a prediction when the wh-phrase indicates that parallelism does not hold (e.g., John told some stories … with which stories…), a potential limit to the prediction of syntactic structures. Crucially, these findings are controversial because the study did not observe processing difficulty when disambiguating input indicated that the predicted continuation was inconsistent with the globally grammatical structure (garden-path effects). The controversial results may be due to a lack of statistical power. Therefore, the present study conducted a large-scale replication study (324 participants and 24 sets of materials). The results revealed that the parser predicts the clausal structure, irrespective of the type of wh-phrase. There was also evidence of garden-path effects, supporting the finding that the parser makes a prediction. These observations suggest that the prediction algorithm inherent in the human parser is more powerful than assumed by the previous study and that the parser attempts to construct globally grammatical structures during revision.