eye tracking

“Where Are the . . .Fixations?:” Grammatical Number Cues Guide Anticipatory Fixations to Upcoming Referents and Reduce Lexical Competition

Listeners make use of contextual cues during continuous speech processing that help overcome the limitations of the acoustic input. These semantic, grammatical, and pragmatic cues facilitate prediction of upcoming words and/or reduce the lexical search space by inhibiting activation of contextually inappropriate words that share phonological information with the target. The current study used the visual world paradigm to assess whether and how listeners use contextual cues about grammatical number during sentence processing by presenting target words in carrier phrases that were grammatically unconstraining (“Click on the . . .”) or grammatically constraining (“Where is/are the . . .”). Prior to the onset of the target word, listeners were already more likely to fixate on plural objects in the “Where are the . . .” context than the “Where is the . . .” context, indicating that they used the construction of the verb to anticipate the referent. Further, participants showed less interference from cohort competitors when the sentence frame made them contextually inappropriate, but still fixated on those words more than on phonologically unrelated distractor words. These results suggest that listeners rapidly and flexibly make use of contextual cues about grammatical number while maintaining sensitivity to the bottom-up input.

Keep Listening: Grammatical Context Reduces But Does Not Eliminate Activation of Unexpected Words

To understand spoken language, listeners combine acoustic-phonetic input with expectations derived from context (Dahan & Magnuson, 2006). Eye-tracking studies on semantic context have demonstrated that the activation levels of competing lexical candidates depend on the relative strengths of the bottom-up input and top-down expectations (cf. Dahan & Tanenhaus, 2004). In the grammatical realm, however, graded effects of context on lexical competition have been predicted (Magnuson, Tanenhaus, & Aslin, 2008), but not demonstrated. In the current eye-tracking study, participants were presented with target words in grammatically unconstraining (e.g., “The word is . . . ”) or constraining (e.g., “They thought about the . . .”) contexts. In the grammatically constrained, identity-spliced trials, in which phonetic information from one token of the target was spliced into another token of the target, fixations to the competitor did not differ from those to distractors. However, in the grammatically constrained, cross-spliced trials, in which phonetic information from the competitor was cross-spliced into the target to increase bottom-up support for that competitor, participants fixated more on contextually inappropriate competitors than phonologically unrelated distractors, demonstrating that sufficiently strong acoustic-phonetic input can overcome contextual constraints. Thus, although grammatical context constrains lexical activation, listeners remain sensitive to the bottom-up input. Taken together, these results suggest that lexical activation is dependent upon the interplay of acoustic-phonetic input and top-down expectations derived from grammatical context.