The Effect of Role Predictability and Word Predictability on Sentence Comprehension

The purpose of this study was to investigate whether the degree of difficulty in the integration of a word into a sentence could be determined by not only how likely the word would be for a given context but also how likely the thematic role associated with the word would be to occur. For our aim, we used dative sentences in Korean in which three arguments (i.e., agent, recipient, and patient/theme) appeared prior to a sentence-final verb. We manipulated 1) the degree of role predictability corresponding to the third argument by scrambling the internal arguments that occurred after an agent and 2) the predictability of words corresponding to the third arguments that was either highly likely or unlikely for a given context. A self-paced moving window reading with a secondary judgment task was conducted. A linear mixed-effect regressions on the reading times of the words corresponding to the third arguments was run while controlling for the effects of lexical frequencies and lengths on the processing of target words. The results from the model revealed that the words were read faster when they were highly likely for given contexts than when they were unlikely, and importantly, that the words were read faster when the roles associated with the words were strongly expected than when they were weakly expected. Our results showed that both role predictability and word predictability had independent effects on the processing of a word in a sentence. We claim that a processing model should be loaded with at least two components that take into account role predictability as well as word predictability.