Left and right-handed dyslexic boys: An empirical test of some assumptions of the Geschwind-Behan hypothesis

Twenty-six dyslexic boys (13 left-handers and 13 right-handers) were tested for hemispheric asymmetry with dichotic listening (DL) and a visual half-field test (VHF). The purpose of the study was an empirical test of the Geschwind-Behan [ Proc. natn. Acad. Sci. USA 79, 5097–5100, 1982] hypothesis of...

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Bibliographic Details
Published in:Neuropsychologia 1989, Vol.27 (2), p.223-231
Main Authors: Hugdahl, Kenneth, Ellertsen, Bj∅rn, Waaler, Per Erik, Kl∅ve, Hallgrim, Hallgrim, Klo̵ve
Format: Article
Language:English
Subjects:
Adolescent
Attention - physiology
Biological and medical sciences
Child clinical studies
Dichotic Listening Tests
Dominance, Cerebral - physiology
Dyslexia - physiopathology
Functional Laterality - physiology
Humans
Male
Medical sciences
Mental Recall - physiology
Pattern Recognition, Visual - physiology
Psychology. Psychoanalysis. Psychiatry
Psychopathology. Psychiatry
Semantics
Testosterone - physiology
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Summary:Twenty-six dyslexic boys (13 left-handers and 13 right-handers) were tested for hemispheric asymmetry with dichotic listening (DL) and a visual half-field test (VHF). The purpose of the study was an empirical test of the Geschwind-Behan [ Proc. natn. Acad. Sci. USA 79, 5097–5100, 1982] hypothesis of a difference in hemispheric asymmetry between left- and right-handed dyslexic boys. Following Geschwind and Behan, left-handedness and dyslexia are caused by a common factor affecting the development of the left hemisphere in utero which results in a right hemisphere dominance. As a consequence, handedness but not language is shifted to the right hemisphere. We therefore predicted that left-handed dyslexics should be superior to right-handed dyslexics on visuospatial tasks, but perform similar to right-handers on verbal tasks. The results revealed a significant right ear advantage (REA) in both groups during a dichotic listening test to verbal stimuli. The left-handed group was however superior to the right-handed group in recognition of visuospatial stimuli presented in the left half-field in a visual half-field test. It is concluded that the results provide some, although weak, support for the Geschwind-Behan hypothesis.
ISSN:0028-3932
1873-3514
DOI:10.1016/0028-3932(89)90173-5