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Visual processing and dyslexia

Everatt, J and Bradshaw, MF and Hibbard, PB (1999) 'Visual processing and dyslexia.' Perception, 28 (2). 243 - 254. ISSN 0301-0066

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Magnocellular-pathway deficits have been hypothesised to be responsible for the problems experienced by dyslexic individuals in reading. However, research has yet to provide a detailed account of the consequences of these deficits or to identify the behavioural link between them and reading disabilities. The aim of the present study was to determine the potential consequences of the magnocellular-pathway deficits for dyslexics in a comprehensive range of visual tasks. Dyslexics and nondyslexics were compared on their ability to (i) perform vernier-acuity and orientation-acuity tasks; (ii) perceive motion by using a range of measures common in the psychophysical literature (D min , D max , and global coherence); and (iii) perceive shapes presented in random-dot stereograms at a range of disparity pedestals, thereby dissociating stereopsis from vergence control. The results indicated no significant differences in performance between the dyslexic and nondyslexic subjects in terms of the visual-acuity measures. In general, dyslexies performed relatively poorly on measures of motion perception and stereopsis, although when considered individually some of the dyslexies performed better than some of the controls. The poor performance of the dyslexies in the stereogram tasks was attributable to a subgroup of dyslexies who also appeared to have severe difficulty with the motion-coherence task. These data are consistent with previous evidence that some dyslexies may have deficits within the magnocellular visual pathway.

Item Type: Article
Subjects: B Philosophy. Psychology. Religion > BF Psychology
Divisions: Faculty of Science and Health > Psychology, Department of
Depositing User: Users 161 not found.
Date Deposited: 13 Feb 2015 21:06
Last Modified: 18 Dec 2017 14:15

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