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How do we read complex words? A neurocognitive morphology priming study.

Poster C124 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port

James Baybas1, Rachel Eggleston1, Ioulia Kovelman1; 1University of Michigan

Reading involves quickly and accurately recognizing long and complex words, such as inter+nation+al+ly. Past research has shown that morphology is an efficient facilitator of recognizing polysyllabic words (Gold & Rastle, 2007). Yet, prior research has been limited to visual stimuli. To understand reading development, it is important to investigate the role of auditory processing that precedes and predicts reading acquisition. The present study offers a systematic inquiry into the audio-visual priming effects of morphology, phonology, and semantics in polysyllabic word reading using functional Near Infrared Spectroscopy (fNIRS). The purpose of the study was to uncover the neurocognitive bases of audio-visual lexical priming and to develop child-friendly protocols that can be used to study literacy development and dyslexia. Fifteen native English-speaking adults with normative reading abilities (U.S.A.; Mage = 21.35, SDage = 3.22) completed an audio-visual lexical priming task. As a preliminary step to developmental research, all stimuli held an early age of acquisition. The experiment used an event-related design: Participants first heard an auditory prime (1200ms), followed by a visual word presentation (2300ms; ISI = 100ms). Participants decided if the visual word was a real word or a nonword (e.g., valley-bleb) and had 2500ms to respond. The three experimental conditions were phonology (e.g., spinach-spin), morphology (e.g., teacher-teach), and semantic (e.g., garbage-trash), with a control condition of unrelated targets (e.g., rotate-coast). fNIRS data were collected and analyzed using General Linear Modeling. All participants completed the task with high accuracy, M = 97.71%, SD = 1.79%. Reaction times indicated that the morphology condition had the strongest priming effect, (M = 631ms, SD = 143ms) followed by phonological priming (M = 693ms, SD = 158ms) and semantic priming (M = 704ms, SD = 143ms). Neuroimaging findings supported existing models of word processing, with MTG response suppression for semantics and STG for phonology. Morphology led to reduced activation in the left IFG, left MTG, right STG, and right IFG relative to control, p < .05. Comparing morphology to semantics further revealed reduced activation in the left IFG, right STG, and right IFG, p < .05. Comparing morphology to phonology, participants showed activation in the left IFG and right IFG, and a reduction in activation in the left STG, p < .05. These findings demonstrate how morphology produces salient priming effects through suppression of the hemodynamic response in the perisylvian brain regions. Our investigation of audio-visual priming effects revealed patterns of results that were generally consistent with those previously obtained for the visual-only lexical priming tasks. The target condition of interest, morphology, in light of its critical facilitative effects in complex word reading, yielded significant priming effects by eliciting the quickest response time (relative to both semantics and phonology) as well as combined activation throughout the perisylvian language regions. The findings inform theories of word processing as well as highlight the importance of morphological competences in word reading and its explicit formal instruction for both emerging readers as well as English second language learners.

Topic Areas: Reading, Morphology

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