The relationship between nonverbal intelligence and Geschwind scores in left-handed subjects.
Under psycho motor hypothesis, the relationship between left-handedness and nonverbal intelligence was studied in left-handed male and female subjects. Handedness was assessed by the Edinburgh Handedness Questionnaire; Geschwind scores (GS) were calculated for each subject. A GS of - 100 indicated consistent left-handedness. Spatial reasoning (nonverbal intelligence) was assessed by the Cattle's Culture Fair Intelligence Test. In the male and female subjects, the IQs increased for GSs from weak up to moderate left-handedness (GSs: -5 to -60), and decreased from moderate up to strong left-handedness (GSs: -60 to -100) linearly; the regression coefficient were found to be statistically significant. Weak-, and strong left-handedness both were associated with lowest scores; the highest scores were found in the subjects with moderate left-handedness (GSs: -55 to -65). It was concluded that the prerequisite for well-developed spatial reasoning should be two-sided development of the brain instead of one-sided dominance, and well functioning parallel processing between two cerebral hemispheres.
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Ataturk University, Medical Faculty, Institute of Physiology, Erzurum, Turkey.
D000328:Adult; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D009633:Nonverbal Communication / Q000502:physiology*