Although the causes of dyslexia are still debated, all researchers agree that the main challenge is to find ways that allow a child with dyslexia to read more words in less time, because reading more is undisputedly the most efficient intervention for dyslexia. Sophisticated training programs exist, but they typically target the component skills of reading, such as phonological awareness. After the component skills have improved, the main challenge remains (that is, reading deficits must be treated by reading more—a vicious circle for a dyslexic child). Here, we show that a simple manipulation of letter spacing substantially improved text reading performance on the fly (without any training) in a large, unselected sample of Italian and French dyslexic children. Extra-large letter spacing helps reading, because dyslexics are abnormally affected by crowding, a perceptual phenomenon with detrimental effects on letter recognition that is modulated by the spacing between letters. Extra-large letter spacing may help to break the vicious circle by rendering the reading material more easily accessible.

Although the dominant approach posits that developmental dyslexia arises from deficits in systems that are exclusively linguistic in nature (i.e., phonological deficit theory), dyslexics show a variety of lower level deficits in sensory and attentional processing. Although their link to the reading disorder remains contentious, recent empirical and computational studies suggest that spatial attention plays an important role in phonological decoding. The present behavioral study investigated exogenous spatial attention in dyslexic children and matched controls by measuring RTs to visual and auditory stimuli in cued-detection tasks. Dyslexics with poor nonword decoding accuracy showed a slower time course of visual and auditory (multisensory) spatial attention compared with both chronological age and reading level controls as well as compared with dyslexics with slow but accurate nonword decoding. Individual differences in the time course of multisensory spatial attention accounted for 31% of unique variance in the nonword reading performance of the entire dyslexic sample after controlling for age, IQ, and phonological skills. The present study suggests that multisensory “sluggish attention shifting”—related to a temporoparietal dysfunction—selectively impairs the sublexical mechanisms that are critical for reading development. These findings may offer a new approach for early identification and remediation of developmental dyslexia.

Focused visuo-spatial attention was studied in 10 developmental dyslexic children with impaired nonword reading, 10 dyslexic children with intact nonword reading, and 12 normally reading children. Reaction times to lateralized visual stimuli in a cued detection task showed that attentional facilitation of the target at the cued location was symmetrical in the three groups. However, dyslexics with impaired nonword reading selectively showed a lack of attentional inhibition for targets at the uncued location in the right visual field. This result was replicated in a second group of 13 dyslexics with impaired nonword reading. Individual differences in the ability of right attentional inhibition across the entire sample of dyslexics accounted for 17% of unique variance in nonword reading accuracy after controlling for individual differences in age, IQ, and phonological skills. A possible explanation based on the role of spatial attention mechanisms in the graphemic parsing process is discussed. Our results suggest that focused visuo-spatial attention may be crucial for nonword decoding.