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 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 visuo-spatial 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.
Hugdahl
K
K
Department of Somatic Psychology, University Hospital, University of Bergen, Norway.
Ellertsen
B
B
Waaler
P E
PE
Kløve
H
H
D000293:Adolescent; D001288:Attention / Q000502:physiology; D004007:Dichotic Listening Tests; D004292:Dominance, Cerebral / Q000502:physiology*; D004410:Dyslexia / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D011939:Mental Recall / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology; D000091402:Prohibitins; D012660:Semantics; D013739:Testosterone / Q000502:physiology*
C000717331:PHB2 protein, human; D000091402:Prohibitins; D013739:Testosterone