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Heritage Bilinguals Adaptively Tune Prediction of Grammatical Category Across Languages

Poster Session D - Monday, March 9, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Noemi X. Diaz^1,2 (), Zoe Yang^1,2, Matthew Traxler^1,2, Tamara Y. Swaab^1,2; ¹University of California-Davis, ²Center for Mind and Brain UC Davis

Prediction is a core function of the brain, allowing efficient processing by pre-activating likely upcoming information. During reading, prediction is evident in the timing and pattern of eye movements. Little is known about how bilinguals predict grammatical categories during reading and whether such prediction generalizes across languages. This study examined word-category prediction by testing how parafoveal preview validity modulated reading behavior in monolinguals and Spanish-English heritage bilinguals. We employed a boundary-change eye-tracking paradigm, manipulating the validity of parafoveal preview and target word categories (noun vs. verb) during reading. English monolinguals and heritage bilinguals tested in L2 read English sentences; a different group of heritage bilinguals, tested in L1, read Spanish sentences. Skipping rate, first-fixation duration, and total time on the target region were analyzed with mixed-effects models. English monolinguals showed preview-validity effects across all measures, indicating that effects of prediction during reading begin at the earliest levels of processing. In contrast, bilinguals tested in English showed preview-validity effects on first-fixation duration and total reading time but not on skipping, suggesting early and late facilitation without riskier eye movements. A significant Group × Preview Validity × Word Category interaction was found in total times, revealing lingering preview-validity effects for nouns but not for verbs, only in bilinguals. In bilinguals assessed in Spanish, preview validity influenced only first-fixation duration. Across bilinguals, greater daily English use predicted stronger preview-validity effects. These findings reveal that the brain’s predictive mechanisms differ between monolinguals and bilinguals and are tuned by bilinguals’ language use and grammatical category.

Topic Area: LANGUAGE: Syntax