Abstract
People with dyslexia have difficulty learning to read and many lack fluent word recognition as adults. In a novel task that borrows elements of the ‘word superiority’ and ‘word inversion’ paradigms, we investigate whether holistic word recognition is impaired in dyslexia. In Experiment 1 students with dyslexia and controls judged the similarity of pairs of 6- and 7-letter words or pairs of words whose letters had been partially jumbled. The stimuli were presented in both upright and inverted form with orthographic regularity and orientation randomized from trial to trial. While both groups showed sensitivity to orthographic regularity, both word inversion and letter jumbling were more detrimental to skilled than dyslexic readers supporting the idea that the latter may read in a more analytic fashion. Experiment 2 employed the same task but using shorter, 4- and 5-letter words and a design where orthographic regularity and stimuli orientation was held constant within experimental blocks to encourage the use of either holistic or analytic processing. While there was no difference in reaction time between the dyslexic and control groups for inverted stimuli, the students with dyslexia were significantly slower than controls for upright stimuli. These findings suggest that holistic word recognition, which is largely based on the detection of orthographic regularity, is impaired in dyslexia.
Highlights
We suggest that this insensitivity to orthographic regularity in dyslexia might usefully be conceptualized as a problem in acquiring a particular type of perceptual expertise, one that relies on holistic processing of words
The study was approved by the Human Research Ethics Committee (HREC) at University College Dublin (UCD); in accordance with the Declaration of Helsinki all participants gave written, informed consent and were advised of their right to withdraw from the study at any time without prejudice
Holistic word processing in dyslexia inversion and with letter jumbling, establishing a gradient of difficulty whereby participants are fastest for upright-real words, fastest for upright-jumbled words, slower again for inverted-real words and slowest for inverted-jumbled words
Summary
Bruck [7]argues that poor phonological processing—a central characteristic of dyslexia [8]—prevents dyslexic readers from accurately noting spelling-sound correspondences in reading which, in turn, prevents them from learning precise orthographic information about words. Others [18] show that while the VWFA is specialized for orthographic regularity at both a coarse scale (distinguishing print from nonprint fonts) and at a finer scale that taps into spelling regularity in normal readers, the VWFA in dyslexic readers does not make this distinction Together these studies point to anomalous development of the VWFA in dyslexia and implicate impaired sensitivity to orthographic regularity as a source of impaired fluency in reading. The effects of inversion and degradation of orthographic regularity were more detrimental to the skilled readers than to those with dyslexia, supporting the idea that dyslexic readers may continue to read in a more analytic fashion into adulthood and never attain full automaticity through the exclusive use of visual word form cues [7]
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