Holistic but with reduced right-hemisphere involvement: The case of dyslexia in Chinese character recognition

Abstract

Recent research on visual object recognition has suggested that the right hemisphere can engage either holistic or part-based processing depending on whether the recognition relies on configural (exact distances among features) or featural information, respectively. Consistent with this finding, expert Chinese reading has been marked by a left-side bias (an indication of righthemisphere lateralization) with decreased holistic processing (as assessed using the composite paradigm) due to its reliance on featural information. Here we examine two common perceptual expertise phenomena in object recognitionholistic processing and left-side biasof Chinese characters in adolescents with developmental dyslexia and matched controls. We found that those with dyslexia showed stronger holistic processing, a weaker left-side bias, and worse performance in Chinese character dictation than controls. This was in contrast to Limited writers (proficient readers with limited writing experience) reported in Tso, Au, and Hsiao (Psychological Science, 25, 1757-1767, who showed stronger holistic processing and worse dictation performance, but the same level of left-side bias as controls. This result demonstrated two different perceptual mechanisms underlying holistic processing: Limited writers' holistic processing may be due to difficulties in de-emphasizing configural information unimportant to Chinese characters, whereas readers with dyslexia may have deficits selectively attending to character components to form appropriate part-based representations in the right hemisphere.

Faces and words are both associated and dissociated as evidenced by visual problems in dyslexia

“…The replicability of this exploratory analysis should be independently verified, but it is possible that weaknesses in reading are associated with greater left hemisphere lateralization of feature-based face processing. This could be consistent with a weaker left-side bias for Chinese character recognition of dyslexic readers in Hong Kong, likely indicating lessened right hemisphere lateralization/greater left hemisphere lateralization 106 . The authors suggest that dyslexic readers may not form appropriate part-based representations in the right hemisphere.…”

“…Similarly, Schmitt et al 122 report that dyslexic children, unlike controls, show no global-to-local interference in the Navon task which the authors interpret as an overreliance on analytic processing as opposed to holistic or global processing. Conversely, compared to typical readers, dyslexic readers showed signs of stronger holistic processing of English words 71 and Chinese characters 106 , 123 , and illiterates process both faces and houses more holistically compared to controls 124 . It is unclear whether these results are inconsistent with our findings of intact global form face processing in dyslexic readers.…”

“…The visual processing of alphabetical scripts, such as Icelandic, and logographic scripts, such as the Chinese writing system, could be qualitatively different. Chinese character recognition also differs from face recognition as it requires extensive writing practice; writing experience could decrease holistic processing of such characters 106 , 123 , 128 in a similar way that face drawing experience appears to decrease the holistic processing of faces 129 . While increased holistic processing of English words in English-speaking dyslexic readers is a bit harder to reconcile with our results, the same authors reported similar holistic processing of faces for typical and dyslexic readers 71 , and impaired holistic word processing in dyslexia has also been reported 72 .…”

Non-monotonic developmental trend of holistic processing in visual expertise: the case of Chinese character recognition

“…Although holistic processing is widely believed to be a general perceptual expertise marker across different domains that involve individualising within-category visual stimuli, several studies suggested the contrary. For example, expert Chinese character recognition is marked by reduced holistic processing (Chung et al, 2018 ; Liu et al, 2016 ), while novices (Hsiao & Cottrell, 2009 ; Tso et al, 2014 ) and Chinese readers with developmental dyslexia (Tso et al, 2020 , 2021 ) recognised Chinese characters with a stronger holistic effect. These findings are also in contrast to the previously observed reduced holistic processing effect associated with face recognition difficulties in the clinical population, such as patients with prosopagnosia (Avidan et al, 2011 ) or autism (Gauthier et al, 2009 ).…”

Music-reading expertise associates with face but not Chinese character processing ability

“…In Chinese orthography, a word retains its meaning even when the spacing between its components is altered, as long as its components and its first-order relationship (i.e., relative positions among character parts) remain unchanged. Tso et al (2020) suggested that featural information (e.g., individual strokes) played a more critical role in Chinese character recognition than did configural information (e.g., exact distances between strokes). Thus, the spatial information is crucial for processing individual musical notations and faces but not for Chinese characters (Ge et al, 2006).…”