Lateral specialization for recognition of words and faces in good and poor readers

An intrahemispheric integration deficit in dyslexia

“…Is it, then, that we should not expect children of this age to exhibit lateral asymmetry on a divided visual field task, or that some other factor operates in this particular case to generate the observed lateral advantage? Examination of the literature on lateral advantage in divided visual field tasks suggests that a right visual field advantage can be found among primary school children (Miller &: Turner, 1973;Olson, 1973;Marcel, Katz &: Smith, 1974;Marcel &: Rajan, 1975;Carmon, Nachshon &: Starinsky, 1976), but that many studies have also failed to find such an effect at least below the age of 10 years (Reitsma, 1975;Yeni-Komshian, Isenberg & Goldberg, 1975;Barroso, 1976;Witelson, 1977b;Broman, 1978;Reynolds & Jeeves, 1978). Studies ha ve even found a left visual field advantage as in the present r e sul ts (Crosland, 1939;Malatesha, 1976).…”

“…The study of Vellutino et al (1975) is discussed by them in these terms, although only on an inference from their data. Similarly, Marcel, Katz and Smith (1974) and Marcel and Rajan (1975) conclude that there is a relative independence of verbal and visuospatial processing in hemisphere specialization shown by poor readers, but it should be noted that as their visuospatial stimuli were non-linguistic, the significance of this independence for dyslexia is unclear. In contrast, a bilateralization of spatial processing which interferes with left hemisphere language lateralization within the left hemisphere was suggested by Witelson (1977a), but again confounding task processing demands, modality of presentation and the nature of the task material.…”

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

“…To reestablish the expected pattern of results, Experiment 2 used blocked presentations of stimuli, as is traditional (Kerschner, 1977;Marcel & Rajan, 1975;Pirozzolo & Rayner, 1979). All nonverbal stimuli were presented together in a sequence, so that the subject knew in advance of a stimulus appearing whether the target would be a dot or a letter.…”

“…The implication considered by Witelson was that dyslexies have their spatial abilities represented bilaterally, and that it is the use of the right cerebral hemisphere for spatial tasks which disrupts their normal language functions. However, Marcel and Rajan (1975) and Pirozzolo and Rayner (1979) failed to find differences between the two groups of readers using a face identification task; therefore, Witelson's hypothesis of bilateral spatial functioning in dyslexia has received minimal support.…”

“…Just as differences between expectations about anticipated stimuli can lead to different strategies of processing, differences between tasks can also induce subjects to adopt specific strategies (Underwood, 1978). With normal readers, small differences in verbal materials and experimental tasks can lead to the appearance of inconsistent visual field advantages (Underwood, 1977;Underwood, Rusted, & Thwaites, 1983), and inconsistencies in reports of asymmetries in the processing of nonverbal stimuli may also be due to small variations in experimental procedures (Marcel & Rajan, 1975;Pirozzolo & Rayner, 1979;Witelson, 1977).…”