Hemispheric Asymmetries in Developmental Dyslexia: Cerebral Structure or Attentional Strategies?

Abstract

Two experiments investigated visual processing asymmetries in normal and dyslexic readers, with unilateral tachistoscopic presentations. The experiments employed randomized or blocked presentations of verbal and nonverbal materials to determine whether previously reported differences between dyslexics and normals were due to structural hemispheric differences or to strategical processing differences. The results indicate that if dyslexics are unable to predict the nature of the stimulus, then they behave as normal readers. Their atypical laterality emerges only when they can adopt a strategy in anticipation of a specific type of stimulus. This leads to the suggestion that developmental dyslexia is associated more with inappropriate modes of thought than it is with hemispheric dysfunction.

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