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

Authors
  • Hugdahl, K
  • Ellertsen, B
  • Waaler, P E
  • Kløve, H
Type
Published Article
Journal
Neuropsychologia
Publisher
Elsevier
Publication Date
Jan 01, 1989
Volume
27
Issue
2
Pages
223–231
Identifiers
PMID: 2927631
Source
Medline
License
Unknown

Abstract

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.

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