Archives of Sexual Behavior

, Volume 37, Issue 6, pp 857–863 | Cite as

Corpus Callosum Anatomy in Right-Handed Homosexual and Heterosexual Men

  • Sandra F. Witelson
  • Debra L. Kigar
  • Anton Scamvougeras
  • David M. Kideckel
  • Brian Buck
  • Peter L. Stanchev
  • Michael Bronskill
  • Sandra Black
Original Paper


The results of several studies have shown that homosexual men have an increased prevalence of non-right-handedness and atypical patterns of hemispheric functional asymmetry. Non-right-handedness in men has been associated with increased size of the corpus callosum (CC), particularly of the isthmus, which is the posterior region of the callosal body connecting parietotemporal cortical regions. We hypothesized that isthmal area would be greater in homosexual men, even among right handers. Twelve homosexual and ten heterosexual healthy young men, all consistently right-handed, underwent a research-designed magnetic resonance imaging scan. We found that the isthmal area was larger in the homosexual group, adding to the body of findings of structural brain differences between homosexual and heterosexual men. This result suggests that right-handed homosexual men have less marked functional asymmetry compared to right-handed heterosexual men. The results also indicate that callosal anatomy and laterality for motoric functions are dissociated in homosexual men. A logistic regression analysis to predict sexual orientation category correctly classified 21 of the 22 men (96% correct classification) based on area of the callosal isthmus, a left-hand performance measure, water level test score, and a measure of abstraction ability. Our findings indicate that neuroanatomical structure and cognition are associated with sexual orientation in men and support the hypothesis of a neurobiological basis in the origin of sexual orientation.


Corpus callosum Magnetic resonance imaging Sexual orientation Homosexuality Functional asymmetry Hand preference Cognition 



This work was supported by research grants NIH NS18954 and MRC 10610 to S.F.W. A.S. held an Ontario Mental Health Foundation fellowship and D.M.K. held an Ontario Graduate Scholarship, while at McMaster University. We thank Dr. Charles Goldsmith, Department of Epidemiology and Biostatistics, McMaster University, for statistical advice.


  1. Allen, L. S., & Gorski, R. A. (1992). Sexual orientation and the size of the anterior commissure in the human brain. Proceedings of the National Academy of Sciences USA, 89, 7199–7202.Google Scholar
  2. Annett, M. (1967). The binomial distribution of right, mixed and left handedness. Quarterly Journal of Experimental Psychology, 19, 327–333.PubMedCrossRefGoogle Scholar
  3. Blanchard, R. (2004). Quantitative and theoretical analyses of the relation between older brothers and homosexuality in men. Journal of Theoretical Biology, 230, 173–187.PubMedCrossRefGoogle Scholar
  4. Bogaert, A. F., & Blanchard, R. (1996). Handedness in homosexual and heterosexual men in the Kinsey interview data. Archives of Sexual Behavior, 25, 373–378.PubMedCrossRefGoogle Scholar
  5. Byne, W., Tobet, S., Mattiace, L. A., Lasco, M. S., Kemether, E., Edgar, M. A., et al. (2001). The interstitial nuclei of the human anterior hypothalamus: An investigation of variation with sex, sexual orientation, and HIV status. Hormones and Behavior, 40, 86–92.PubMedCrossRefGoogle Scholar
  6. Clarke, J. M., Lufkin, R. B., & Zaidel, E. (1993). Corpus callosum morphometry and dichotic listening performance: Individual differences in functional interhemispheric inhibition? Neuropsychologia, 31, 547–557.PubMedCrossRefGoogle Scholar
  7. Cowell, P. E., Kertesz, A., & Denenberg, V. H. (1993). Multiple dimensions of handedness and the human corpus callosum. Neurology, 43, 2353–2357.PubMedGoogle Scholar
  8. Ekstrom, R. B., French, J. W., Harman, H. H., & Dermen, D. (1976). Kit of factor-referenced cognitive tests. Princeton, NJ: Educational Testing Service.Google Scholar
  9. Gladue, B. A., Beatty, W. W., Larson, J., & Staton, R. D. (1990). Sexual orientation and spatial ability in men and women. Psychobiology, 18, 101–108.Google Scholar
  10. Hamer, D. H., Hu, S., Magnuson, V. L., Hu, N., & Pattatucci, A. M. (1993). A linkage between DNA markers on the X chromosome and male sexual orientation. Science, 261, 321–327.PubMedCrossRefGoogle Scholar
  11. Hines, M., Brook, C., & Conway, G. S. (2004). Androgen and psychosexual development: Core gender identity, sexual orientation and recalled childhood gender role behavior in women and men with congenital adrenal hyperplasia (CAH). Journal of Sex Research, 41, 75–81.PubMedCrossRefGoogle Scholar
  12. Hofer, S., & Frahm, J. (2006). Topography of the human corpus callosum revisited: Comprehensive fiber tractography using diffusion tensor magnetic resonance imaging. Neuroimage, 32, 989–994.PubMedCrossRefGoogle Scholar
  13. Hulshoff Pol, H. E., Schnack, H. G., Posthuma, D., Mandl, R. C. W., Baaré, W. F., van Oel, C., et al. (2006). Genetic contributions to human brain morphology and intelligence. Journal of Neuroscience, 26, 10235–10242.PubMedCrossRefGoogle Scholar
  14. Kinsey, A. C., Pomery, W. B., & Martin, C. E. (1948). Sexual behavior in the human male. Philadelphia, PA: Saunders.Google Scholar
  15. Kolb, B., & Whishaw, I. Q. (2003). Fundamentals of human neuropsychology (5th ed.). New York: W. H. Freeman.Google Scholar
  16. Lalumiére, M. L., Blanchard, R., & Zucker, K. J. (2000). Sexual orientation and handedness in men and women: A meta-analysis. Psychological Bulletin, 126, 575–592.PubMedCrossRefGoogle Scholar
  17. Lasco, M. S., Jordan, T. J., Edgar, M. A., Petito, C. K., & Byne, W. (2002). A lack of dimorphism of sex or sexual orientation in the human anterior commissure. Brain Research, 936, 95–98.PubMedCrossRefGoogle Scholar
  18. LeVay, S. (1991). A difference in hypothalamic structure between heterosexual and homosexual men. Science, 253, 1034–1037.PubMedCrossRefGoogle Scholar
  19. Lindesay, J. (1987). Laterality shift in homosexual men. Neuropsychologia, 25, 965–969.CrossRefGoogle Scholar
  20. Luders, E., Rex, D. E., Narr, K. L., Woods, R. P., Jancke, L., Thompson, P. M., et al. (2003). Relationships between sulcal asymmetries and corpus callosum size: Gender and handedness effects. Cerebral Cortex, 13, 1084–1093.PubMedCrossRefGoogle Scholar
  21. McCormick, C. M., & Witelson, S. F. (1991). A cognitive profile of homosexual men compared to heterosexual men and women. Psychoneuroendocrinology, 16, 459–473.PubMedCrossRefGoogle Scholar
  22. McCormick, C. M., & Witelson, S. F. (1994). Functional cerebral asymmetry and sexual orientation in men and women. Behavioral Neuroscience, 108, 525–531.PubMedCrossRefGoogle Scholar
  23. McCormick, C. M., Witelson, S. F., & Kingstone, E. (1990). Left-handedness in homosexual men and women: Neuroendocrine implications. Psychoneuroendocrinology, 15, 69–76.PubMedCrossRefGoogle Scholar
  24. McFadden, D., & Pasanen, E. G. (1998). Comparison of the auditory systems of heterosexuals and homosexuals: Click-evoked otoacoustic emissions. Proceedings of the National Academy of Sciences USA, 95, 2709–2713.CrossRefGoogle Scholar
  25. Morton, B. E., & Rafto, S. E. (2006). Corpus callosum size is linked to dichotic deafness and hemisphericity, not sex or handedness. Brain and Cognition, 62, 1–8.PubMedCrossRefGoogle Scholar
  26. Mustanski, B. S., Chivers, M. L., & Bailey, J. M. (2002). A critical review of recent biological research on human sexual orientation. Annual Review of Sex Research, 13, 89–140.PubMedGoogle Scholar
  27. Peng, C.-Y. J., So, T.-S. H., Stage, F. K., & St. John, E. P. (2002). The use and interpretation of logistic regression in higher education journals. Research in Higher Education, 43, 259–293.CrossRefGoogle Scholar
  28. Pillard, R. C., & Bailey, J. M. (1998). Human sexual orientation has a heritable component. Human Biology, 70, 347–365.Google Scholar
  29. Rahman, Q., & Wilson, G. D. (2003). Large sexual-orientation-related differences in performance on mental rotation and judgment of line orientation tasks. Neuropsychology, 17, 25–31.PubMedCrossRefGoogle Scholar
  30. Rice, G., Anderson, C., Risch, N., & Ebers, G. (1999). Male homosexuality: Absence of linkage to microsatellite markers at Xq28. Science, 284, 665–667.PubMedCrossRefGoogle Scholar
  31. Sanders, G., & Ross-Field, L. (1986). Sexual orientation and visuo-spatial ability. Brain and Cognition, 5, 280–290.PubMedCrossRefGoogle Scholar
  32. Sanders, G., & Wright, M. (1997). Sexual orientation differences in cerebral asymmetry and in the performance of sexually dimorphic cognitive and motor tasks. Archives of Sexual Behavior, 26, 463–480.PubMedCrossRefGoogle Scholar
  33. Savic, I., Berglund, H., & Lindstrom, P. (2005). Brain responses to putative pheromones in homosexual men. Proceedings of the National Academy of Sciences USA, 102, 7356–7361.CrossRefGoogle Scholar
  34. Scamvougeras, A., Kigar, D. L., Jones, D., Weinberger, D. R., & Witelson, S. F. (2003). Size of the human corpus callosum is genetically determined: An MRI study in mono and dizygotic twins. Neuroscience Letters, 338, 91–94.PubMedCrossRefGoogle Scholar
  35. Shipley, W. C. (1940). A self-administering scale for measuring intellectual impairment and deterioration. Journal of Psychology, 9, 371–377.CrossRefGoogle Scholar
  36. Steinmetz, H., Jancke, L., Kleinschmidt, A., Schlaug, G., Volkmann, J., & Huang, Y. (1992). Sex but no hand difference in the isthmus of the corpus callosum. Neurology, 42, 749–752.PubMedGoogle Scholar
  37. Swaab, D. F., & Hofman, M. A. (1990). An enlarged suprachiasmatic nucleus in homosexual men. Brain Research, 537, 141–148.PubMedCrossRefGoogle Scholar
  38. Tapley, S. M., & Bryden, M. P. (1985). A group test for the assessment of performance between the hands. Neuropsychologia, 23, 215–221.PubMedCrossRefGoogle Scholar
  39. Thomas, H., Jamison, W., & Hummel, D. D. (1973). Observation is insufficient for discovering that the surface of still water is invariantly horizontal. Science, 181, 173–174.PubMedCrossRefGoogle Scholar
  40. Thurstone, L. L., & Thurstone, T. G. (1962). Primary mental abilities for grades 9–12. Chicago, IL: Science Research Associates.Google Scholar
  41. Tuncer, M. C., Hatipoglu, E. S., & Ozates, M. (2005). Sexual dimorphism and handedness in the human corpus callosum based on magnetic resonance imaging. Surgical and Radiologic Anatomy, 27, 254–259.PubMedCrossRefGoogle Scholar
  42. van Anders, S. M., & Hampson, E. (2005). Testing the prenatal androgen hypothesis: Measuring digit ratios, sexual orientation, and spatial abilities in adults. Hormones and Behavior, 47, 92–98.PubMedCrossRefGoogle Scholar
  43. Wegesin, D. J. (1998). Event-related potentials in homosexual and heterosexual men and women: Sex-dimorphic patterns in verbal asymmetries and mental rotation. Brain and Cognition, 36, 73–92.PubMedCrossRefGoogle Scholar
  44. Westerhausen, R., Walter, C., Kreuder, F., Wittling, R. A., Schweiger, E., & Wittling, W. (2003). The influence of handedness and gender on the microstructure of the human corpus callosum: A diffusion-tensor magnetic resonance imaging study. Neuroscience Letters, 351, 99–102.PubMedCrossRefGoogle Scholar
  45. Witelson, S. F. (1989). Hand and sex differences in the isthmus and genu of the human corpus callosum: A postmortem morphological study. Brain, 112, 799–835.PubMedCrossRefGoogle Scholar
  46. Witelson, S. F., & Nowakowski, R. S. (1991). Left out axons make men right: A hypothesis for the origin of handedness and functional asymmetry. Neuropsychologia, 29, 327–333.PubMedCrossRefGoogle Scholar
  47. Yokota, Y., Kawamura, Y., & Kameya, Y. (2005). Callosal shapes at the midsagittal plane: MRI differences of normal males, normal females, and GID. In Proceedings of the 2005 IEEE engineering in medicine and biology 27th annual conference, Shangai, China, pp. 3055–3058.Google Scholar
  48. Zucker, K. J., & Bradley, S. J. (1995). Gender identity disorder and psychosexual problems in children and adolescents. New York: Guilford Press.Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Sandra F. Witelson
    • 1
  • Debra L. Kigar
    • 1
  • Anton Scamvougeras
    • 2
  • David M. Kideckel
    • 3
  • Brian Buck
    • 4
  • Peter L. Stanchev
    • 5
  • Michael Bronskill
    • 6
  • Sandra Black
    • 4
  1. 1.Department of Psychiatry and Behavioural NeurosciencesMcMaster UniversityHamiltonCanada
  2. 2.Department of PsychiatryUniversity of British ColumbiaVancouverCanada
  3. 3.Institute of Medical ScienceUniversity of TorontoTorontoCanada
  4. 4.Division of Neurology, Department of MedicineSunnybrook Health Sciences CentreTorontoCanada
  5. 5.Department of Science and MathematicsKettering UniversityFlintUSA
  6. 6.Imaging ResearchSunnybrook Health Sciences CentreTorontoCanada

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