Recognition of verbal and non-verbal stimuli in the lateral visual fields in normal children and those manifesting learning disabilities



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In 1970, Koetting reported on an investigation concerning the ability to recognize words in each of the four lateral visual fields, noting that there is a significant superiority with respect to this ability in both components of the right field—especially the nasal field of the left eye. There is also evidence that such differences in recognition are a product of learning to read, and that they do not occur with non-verbal targets. To explore these latter contentions, this study was introduced in an attempt to demonstrate differences between groups of normal children and those designated as having learning-disabilities through use of verbal targets; and, the absence or other differences in the phenomenon in both groups using non-verbal targets. It involved the discrete tachistoscopic presentation of verbal and non-verbal stimuli in the four lateral parafoveal fields at a fixed lateral displacement from a point of fixation. Subjects were forty ten-year-old children—32 in the normal group and 8 in the learning-disabilities group. A superiority of performance was found in the total right visual field for both verbal and non-verbal treatments in normal children at the .05 and .01 level of confidence, respectively; it was absent in children manifesting learning-disabilities. This evidence suggests that in normal children the phenomenon in which language skills are observed to be better established in the left cerebral hemisphere is only one manifestation of an overall propensity for the left cerebral hemisphere to process gestalts, and that this propensity is not as well established in ten-year-old children having learning-disabilities as in ten-year-old normal children. There are indications that in learning-disabilities children the decrement in the ability to more efficiently process verbal material is in the left-nasal component of the right field, and non-verbal material in both the left-nasal and right-temporal components. There are also indications of a superiority for processing verbal gestalts via inputs from the left-nasal field and from the right-temporal field for non-verbal gestalts, favoring the normal group; and, an increased capacity in the left-temporal field with respect to both verbal and non-verbal gestalts favoring the learning-disabilities group. Supported are positions that the portion of the brain used for processing a given type of input is determined by the nature of the input, and that this triggering mechanism is at least partially learned during a child's development.