ABSTRACT
We explored implicit learning in a group of typically developing and developmental dyslexic primary school children (9-12 y) using a modified artificial grammar learning task. Performance was calculated using two measures of performance: a perfect free recall (PFR) score and a grammaticality judgment score. Both groups of children required the same amount of exposure to memorize the items (i.e. PFR performance) (t((30))=1.620, p>0.05; p-value reported two-tailed). However, repeated measures ANOVA (Participant type x Grammaticality x Chunk strength) revealed a Participant type effect for grammaticality judgment scores (F((1,30))=4.521, p<0.05; p-value reported two-tailed). Typically developing children showed above chance performance in terms of both grammaticality and chunk strength of the stimuli. Children with developmental dyslexia on the other hand, failed to show implicit learning irrespective of the substring characteristics (i.e. grammaticality or chunk strength). We propose that children with developmental dyslexia may be impaired in their implicit rule abstraction mechanism, which can partially explain their persistent reading problems.
Subject(s)
Dyslexia/epidemiology , Learning Disabilities/epidemiology , Child , Comorbidity , Female , Humans , Learning Disabilities/diagnosis , Male , Prevalence , Speech Reception Threshold TestABSTRACT
Rapid automatized naming (RAN; Denckla & Rudel, 1976) tasks are consistent predictors of fluency that also discriminate between dyslexic and nondyslexic reading groups. The component processes of RAN that are responsible for its relationship with reading ability remain underspecified, however. We report a study on dyslexic and nondyslexic adult groups that experimentally manipulated RAN formats to elucidate how different components of RAN differentially influence dyslexic and nondyslexic performance. The dyslexic group showed a pervasive deficit in rapid access of individually presented items. Additionally, they showed a significant impairment when multiple items were presented, whereas nondyslexic readers showed marginal facilitation for this format. We discuss the implications of these findings with respect to reading-group differences in reading fluency.
Subject(s)
Dyslexia/diagnosis , Pattern Recognition, Visual , Phonetics , Reaction Time , Reading , Semantics , Verbal Behavior , Attention , Dyslexia/psychology , Female , Fixation, Ocular , Humans , Male , Orientation , Reference Values , Saccades , Serial Learning , Young AdultABSTRACT
Developmental dyslexia is often characterized by a visual deficit, but the nature of this impairment and how it relates to reading ability is disputed (Brain 2003; 126: 841-865). In order to investigate this issue, we compared groups of adults with and without dyslexia on the Ternus, visual-search and symbols tasks. Dyslexic readers yielded more errors on the visual-search and symbols tasks compared with non-dyslexic readers. A positive correlation between visual-search and symbols task performance suggests a common mechanism shared by these tasks. Performance on the visual-search and symbols tasks also correlated with non-word reading and rapid automatized naming measures, and visual search contributed independent variance to non-word reading. The Ternus task did not discriminate reading groups nor contributed significant variance to reading measures. We consider how visual-attention processes might underlie specific component reading measures.
Subject(s)
Discrimination Learning , Dyslexia/diagnosis , Pattern Recognition, Visual , Perceptual Disorders/diagnosis , Reading , Visual Perception , Adolescent , Adult , Female , Humans , Male , Motion Perception , Orientation , Perceptual Disorders/psychology , Problem Solving , Reaction Time , Young AdultABSTRACT
We argue that the vertical division of the fovea and the hemispheric division of the brain condition reading, and that hemispheric desynchronization is a proximal cause of dyslexia. We predict that dyslexics' fixation behaviour in reading accommodates to problematic hemispheric transfer/coordination, with fixations projecting more letter-information directly to the left hemisphere to facilitate processing. We analysed eye movements of 24 dyslexics and 24 normal readers. Dyslexics fixated closer to word beginning than did normal readers, projecting more of the word directly to the left hemisphere. Both groups produced comparable fixation durations at the beginning of the word; further into the word the dyslexics produced longer fixation durations. The results support a model of dyslexia based on hemispheric desynchronization.
