The spatial distribution of visual attention in developmental dyslexia

The present study investigated the spatial distribution of visual attention in dyslexic and normally reading children. The performances of the two gro ups were investigated using two different paradigms. In experiment 1 we ana lyzed the distribution of processing resources both inside and outside the focus of visual attention by simply recording reaction times to the detecti on of a white dot target projected at different eccentricities from the fov ea. The distribution of attentional resources differed significantly betwee n the two groups of children. The eccentricity of the stimulus was signific ant only for normally reading children - who showed a normal gradient - as it influenced their detection speed, whereas it had no effect on dyslexic c hildren, who exhibited a diffused distribution of visual processing resourc es inside the visual field. In experiment 2 we studied the distributed (unf ocused) mode of attention in a visual search task by measuring reaction tim es to a target stimulus inside a large configuration with a variable number of distractors. Results show that as compared to normal children dyslexics are better able to distribute their attentional resources diffusely. Our c onclusion is that reading disability may be characterized by a diffused dis tribution of visual processing resources. These data might be interpreted i n the framework of studies on magnocellular deficits in dyslexia, whereby t he anomalous distribution of visual attention might explain how transient p athway functioning influences the reading process.