Shao-Chin Hung¹, Hsiao-Lan Sharon Wang², Chien-Chung Chen¹; ¹National Taiwan University, ²National Taiwan Normal University

Humans identify global figures faster than local ones. This global precedence is challenged in dyslexics, who show a local-before-global perception (Franceschini et al., 2017). Here we investigated the stimulus dependence of the global and local perception in three groups: Mandarin-speaking juveniles with developmental dyslexia, age-matched neurotypical juveniles (12-17 years), and neurotypical non-Chinese-reading adults (23-27 years). Participants completed a novel Navon task requiring judgments of whether the global or local elements of stimuli presented bilaterally were identical. Experiment 1 used large geometric shapes (circles, diamonds, or triangles) composed of smaller ones, and Experiment 2 used analogous stimuli constructed from Chinese characters. Across both experiments, all groups showed a global precedence effect, with increased accuracy in global tasks compared to local tasks. In Experiment 1, both juvenile groups showed a congruency effect for both task types, responding more accurately while global and local geometric shapes matched, indicating mutual interference across levels. In Experiment 2, the congruency effect appeared only in local tasks, indicating interference from the global to the local level but not vice versa. The dyslexics showed inferior local perception relative to the neurotypical juvenile, particularly when viewing Chinese characters. The non-readers exhibited global-local performance patterns similar to neurotypical juveniles even when processing Chinese characters. These findings suggest that the impaired reading performance in dyslexics may arise from deficits in visual word form analysis rather than from language-specific knowledge. Overall, we found no evidence of local precedence in dyslexia for either geometric shapes or Chinese characters. The impaired local perception of Chinese characters observed in dyslexics may suggest specialized channels for visual word form processing.

Acknowledgements: NSTC 114-2410-H-003-137