Expectation and integration processes in flexible word order processing: interactions of voice and verb semantics in Tagalog

A key recent discussion in the sentence processing literature centers on the primary mechanism of the human processing system: the extent to which it engages in a consistent and immediate process of generating and revising expectations, versus regular incorporation of new input with the developing representations through integration processes. The current study probes these two mechanisms by investigating declarative sentence processing in the understudied verb-initial, flexible word order language Tagalog. Tagalog verbs contain grammatical information that is probabilistically informative of the likely word order of the sentence. Experiment 1 (sentence completion task) showed that Tagalog word order completions for the first and second noun phrases were driven by a preference to place the agent and the syntactically prominent argument (pivot) in the first and second argument positions, respectively, and that such preferences vary by grammatical voice and semantic verb class type. Completions in Experiment 1 were used to compute for expectation-based conditional probabilities and surprisal for nominal markers of the upcoming first and second arguments, conditioned by voice and verb class. These values were then used to test how online reading measures at the first and second nominal markers in Experiment 2 (word-by-word self-paced reading) reflected expectation and integration-based processes. Overall online measures demonstrated dynamic incremental effects across the sentence that were only partially consistent with expectation-based hypotheses. The results highlight the importance of incorporating integration processes in sentence processing models.