Abstract
Five studies have examined the relationship between sexual orientation and the relative lengths of the 2nd and 4th fingers (the 2D:4D ratio). Although differences have commonly been found between heterosexuals and homosexuals, the direction of the difference has not been consistent across studies. The original data from all five studies were reanalyzed in a search for possible explanations of the discrepancies. Because ethnicity is known to affect the 2D:4D ratio, the reanalysis focused on participants who identified themselves as White or Caucasian, the ethnic group that was most numerous in all of the studies. Age differences did not account for the discrepancies. Differences in variability within different groups were minor. One interesting result to emerge from the reanalysis was that the 2D:4D ratios for the homosexual groups were relatively similar across studies. It was the 2D:4D values for the heterosexual participants that varied most, particularly between the USA and the British studies, and these were responsible for many of the discrepancies in the conclusions across studies. The constancy of the 2D:4D ratio for the White homosexuals did not appear to extend to homosexuals of three other ethnicities, and there were also subpopulation differences related to right or left hands.
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References
Blanchard, R. (1997). Birth order and sibling sex ratio in homosexual versus heterosexual males and females. Annual Review of Sex Research, 8, 27–67.
Blanchard, R. (2004). Quantitative and theoretical analyses of the relation between older brothers and homosexuality in men. Journal of Theoretical Biology, 230, 173–187.
Brown, W. M., Finn, C. J., Cooke, B. M., & Breedlove, S. M. (2002a). Differences in finger length ratios between self-identified “butch” and “femme” lesbians. Archives of Sexual Behavior, 31, 117–121.
Brown, W. M., Hines, M., Fane, B. A., & Breedlove, S. M. (2002b). Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia. Hormones and Behavior, 42, 380–386.
Buck, J. J., Williams, R. M., Hughes, I. A., & Acerini, C. L. (2003). In-utero androgen exposure and 2nd and 4th digit length ratio–comparisons between healthy controls and females with classical congenital adrenal hyperplasia. Human Reproduction, 18, 976–979.
Cohen, J. (1992). A power primer. Psychological Bulletin, 112, 155–159.
Collaer, M. L., & Hines, M. (1995). Human behavioral sex differences: A role for gonadal hormones during early development? Psychological Bulletin, 118, 55–107.
Csatho, A., Osvath, A., Bicsak, E., Karadi, K., Manning, J., & Kallai, J. (2003). Sex role identity related to the ratio of second to fourth digit length in women. Biological Psychology, 62, 147–156.
Fink, B., Neave, N., & Manning, J. T. (2003). Second to fourth digit ratio, body mass index, waist-to-hip ratio, and waist-to-chest ratio: Their relationships in heterosexual men and women. Annals of Human Biology, 30, 728–738.
Hall, L. S., & Love, C. T. (2003). Finger-length ratios in female monozygotic twins discordant for sexual orientation. Archives of Sexual Behavior, 32, 23–28.
Harris, E. F., Aksharanugraha, K., & Behrents, R. G. (1992). Metacarpophalangeal length changes in humans during adulthood: A longitudinal study. American Journal of Physical Anthropology, 87, 263–275.
Iguchi, T., Watanabe, H., & Katsu, Y. (2001). Developmental effects of estrogenic agents on mice, fish, and frogs: A mini-review. Hormones and Behavior, 40, 248–251.
Koehler, N., Simmons, L. W., & Rhodes, G. (2004). How well does second-to-fourth-digit ratio in hands correlate with other indications of masculinity in males? Biology Letters, 271, S296–S298.
Kondo, T., Zakany, J., Innis, J. W., & Duboule, D. (1997). Of fingers, toes and penises. Nature, 390, 29.
Lippa, R. A. (2003). Are 2D:4D finger-length ratios related to sexual orientation? Yes for men, no for women. Journal of Personality and Social Psychology, 85, 179–188.
Litingtung, Y., Dahn, R. D., Li, Y., Fallon, J. F., & Chiang, C. (2002). Shh and Gli3 are dispensable for limb skeleton formation but regulate digit number and identity. Nature, 418, 979–983.
Lutchmaya, S., Baron-Cohen, S., Raggatt, P., Knickmeyer, R., & Manning, J. T. (2004). 2nd to 4th digit ratios, fetal testosterone and estradiol. Early Human Development, 77, 23–28.
Manning, J. T. (2002). Digit ratio: A pointer to fertility, behavior, and health. New Brunswick, NJ: Rutgers University Press.
Manning, J. T., Baron-Cohen, S., Wheelwright, S., & Sanders, G. (2001). The 2nd to 4th digit ratio and autism. Developmental Medicine and Child Neurology, 43, 160–164.
Manning, J. T., Bundred, P. E., & Flanagan, B. F. (2002). The ratio of 2nd to 4th digit length: A proxy for transactivation activity of the androgen receptor gene? Medical Hypotheses, 59, 334–336.
Manning, J. T., Bundred, P. E., Newton, D. J., & Flanagan, B. F. (2003). The 2nd to 4th digit ratio and variation in the androgen receptor gene. Evolution and Human Behavior, 24, 399–405.
Manning, J. T., Fink, B., Neave, N., & Caswell, N. (2005). Photocopies yield lower digit ratios (2D:4D) than direct finger measurements. Archives of Sexual Behavior, 34, 329–333.
Manning, J. T., & Robinson, S. J. (2003). 2nd to 4th digit ratio and a universal mean for prenatal testosterone in homosexual men. Medical Hypotheses, 61, 303–306.
Manning, J. T., Scutt, D., Wilson, J., & Lewis-Jones, D. I. (1998). The ratio of 2nd to 4th digit length: A predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen. Human Reproduction, 13, 3000–3004.
Martin, J. T., & Nguyen, D. H. (2004). Anthropomorphic analysis of homosexuals and heterosexuals: Implications for early hormone exposure. Hormones and Behavior, 45, 31–39.
McFadden, D. (2002). Masculinization effects in the auditory system. Archives of Sexual Behavior, 31, 93–105.
McFadden, D., & Shubel, E. (2002). Relative lengths of fingers and toes in human males and females. Hormones and Behavior, 42, 492–500.
McFadden, D., Westhafer, J. G., Pasanen, E. G., Tucker, D. M., & Carlson, C. L. (2003). Otoacoustic emissions measured in children diagnosed with attention-deficit/hyperactivity disorder [Abstract]. Journal of the Acoustical Society of America, 114, 2337–2338.
McFadden, D., Westhafer, J. G., Pasanen, E. G., Carlson, C. L., & Tucker, D. M. (2005). Physiological evidence of hypermasculinization in boys with the inattentive subtype of attention-deficit/hyperactivity disorder (ADHD). Clinical Neuroscience Research, in press.
McIntyre, M. H. (2003). Digit ratios, childhood gender role behavior, and erotic role preference of gay men [Letter-to-the-Editor]. Archives of Sexual Behavior, 32, 495–497.
Ökten, A., Kalyoncu, M., & Yaris, N. (2002). The ratio of second- and fourth-digit lengths and congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Early Human Development, 70, 47–54.
Ottinger, M. A., Abdelnabi, M. A., Henry, P., McGary, S., Thompson, N., & Wu, J. M. (2001). Neuroendrocrine and behavioral implications of endocrine disrupting chemicals in quail. Hormones and Behavior, 40, 234–247.
Rahman, Q., & Wilson, G. D. (2003a). Sexual orientation and the 2nd to 4th finger length ratio: Evidence for organizing effects of sex hormones or developmental instability? Psychoneuroendocrinology, 28, 288–303.
Rahman, Q., & Wilson, G. D. (2003b). Born gay? The psychobiology of human sexual orientation. Personality and Individual Differences, 34, 1337–1382.
Robinson, S. J., & Manning, J. T. (2000). The ratio of 2nd to 4th digit length and male homosexuality. Evolution and Human Behavior, 21, 333–345.
Tortorice, J. L. (2002). Written on the body: Butch/femme lesbian gender identity and biological correlates. Unpublished doctoral dissertation, Rutgers University.
Williams, T. J., Pepitone, M. E., Christensen, S. E., Cooke, B. M., Huberman, A. D., Breedlove, N. J., et al. (2000). Finger-length ratios and sexual orientation. Nature, 404, 455–456.
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McFadden, D., Loehlin, J.C., Breedlove, S.M. et al. A Reanalysis of Five Studies on Sexual Orientation and the Relative Length of the 2nd and 4th Fingers (the 2D:4D Ratio). Arch Sex Behav 34, 341–356 (2005). https://doi.org/10.1007/s10508-005-3123-9
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DOI: https://doi.org/10.1007/s10508-005-3123-9