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Handedness concordance and intelligence discrepancies in identical twins
C M Clark1, H Klonoff, J S Tyhurst
1Department of Psychiatry, University of British Columbia, Vancouver, Canada.
Summary
This study examined intelligence discrepancies in identical twins. No evidence supported the hypothesis that differing handedness patterns correlate with intelligence variations, suggesting congenital factors may not cause such dissociation.
Area of Science:
- Behavioral Genetics
- Neuroscience
- Psychology
Background:
- Identical twins share genetics, but variations in traits like handedness occur.
- Previous theories suggest congenital factors or brain insults may influence handedness and intelligence discordance.
Purpose of the Study:
- To investigate if intelligence discrepancies differ between identical twins concordant and discordant for handedness.
- To test hypotheses linking congenital factors to handedness and intelligence dissociation.
Main Methods:
- Examined eight sets of identical twins.
- Measured intelligence and assessed handedness concordance/discordance.
Main Results:
- No significant evidence found to support the hypotheses.
- In one set with a large intelligence gap, precise handedness determination was not possible for the lower IQ twin.
Conclusions:
- The study did not find support for congenital factors causing dissociation between handedness and intelligence in identical twins.
- Further research is needed, particularly in cases with significant intelligence discrepancies and ambiguous handedness.