M.A. (Psychology) / The goal of the present study was to determine whether there exist any differences in cognitive skills between left-handed dyslexic boys and righthanded dyslexic boys with left hemisphere speech representation. The comparison was made in terms of their verbal and visuo-spatial skills. The motivation for this study resulted from a hypothesis that was formulated by Geschwind and Behan (1982). The hypothesis states that there exists a difference in functional hemispheric asymmetry between left-handed and righthanded dyslexic boys with left hemispheric language representation. By virtue of their explanation of dyslexia in terms of a prenatal hyper secretion of the hormone called testosterone, Geschwind and Behan state that left-handed dyslexic boys will perform better than right-handed dyslexic boys on visuospatial tasks. An empirical study was performed in order to compare the verbal and visuospatial skills of left-handed and right-handed dyslexic boys. Twenty-six lefthanded and 26 right-handed dyslexic boys served as the experimental subjects. All the subjects had left hemispheric language representation. The selection of the experimental subjects was done by means of the dichotic listening technique as well as with the Harris test of lateral dominance. The nine subtests of the Senior South African Individual Scale-Revised served as measuring-instrument. The first five subscales represented the verbal cognitive skills. The visuo-spatial skills were measured with subtests six to nine. The data were statistically analysed by means of Hotelling's T2-test and Student's t-tests. The results indicated that there were no statistically significant differences between left-handed and right-handed dyslexic boys with left hemispheric language representation in terms of any of the verbal and visuo-spatial subtests. The relationship between hand preference, functional hemispheric asymmetry and dyslexia is elucidated by the present study which rejects the GeschwindBehan hypothesis that there exists a difference in functional hemispheric asymmetry between left-handed and right-handed dyslexic boys. A previous study (Hugdahl et aI., 1989) accepted this hypothesis. Further research is thus necessary in order to determine the validity of the Geschwind-Behan hypothesis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:10973 |
| Date | 08 May 2014 |
| Creators | Pelser, Marié E. |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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