Digit ratio (2D:4D), dominance, reproductive success, asymmetry, and sociosexuality in the BBC Internet study. American Journal of Human Biology, 20, 451-461

Department of Psychology, University of Central Lancashire, Preston, United Kingdom.
American Journal of Human Biology (Impact Factor: 1.7). 07/2008; 20(4):451-61. DOI: 10.1002/ajhb.20767
Source: PubMed


Digit ratio (2D:4D) may be a correlate of prenatal sex steroids, and has been linked to traits, which are influenced by fetal testosterone and estrogen. Here we consider such links in a large Internet study of sex differences (the BBC Internet Study) in which finger lengths were self-measured. Consistent with lab-based findings the 2D:4D in this study shows sexual dimorphism, ethnic differences and higher dimorphism of right 2D:4D than left, thereby indicating that 2D:4D does measure real between-participant variation. High error in self-measurement of fingers reduces effect sizes. However, the large sample size gives assurance that significant effects are likely to be real. We controlled for ethnicity and sexual orientation by considering White heterosexuals only (153,429 participants). Sexual dimorphism was confirmed in 2D:4D and for the difference of right-left 2D:4D. After Bonferroni correction we found highly significant relationships with low effect sizes as follows. In males and females there were negative associations between 2D:4D and dominance. In males there were negative associations between 2D:4D and family size and factors associated with reproductive success. For females these associations were positive. For asymmetry we found U-shaped relationships with 2D:4D in both males and females. We found no relationship between 2D:4D and promiscuity (sociosexuality). In total, we considered 48 relationships and found 29 to be significant. We compare our findings with a similar study reported by Putz et al. (2004), which found only 2 out of 57 correlations to be significant and discuss possible reasons for the discrepancies between the studies.

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    • "Consistent with our specific hypotheses, feminist activists exhibited a significantly more masculinized 2D:4D ratio relative to both Swedish and aggregate comparison groups, a substantially higher level of Directiveness than both the male and female Australian samples, and within-sample correlations between these variables. Consistent with previous research, there were also significant correlations between the hands (Hampson et al., 2008; Manning and Fink, 2008; Butovskaya et al., 2010) and stronger correlations "
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    ABSTRACT: The feminist movement purports to improve conditions for women, and yet only a minority of women in modern societies self-identify as feminists. This is known as the feminist paradox. It has been suggested that feminists exhibit both physiological and psychological characteristics associated with heightened masculinization, which may predispose women for heightened competitiveness, sex-atypical behaviors, and belief in the interchangeability of sex roles. If feminist activists, i.e., those that manufacture the public image of feminism, are indeed masculinized relative to women in general, this might explain why the views and preferences of these two groups are at variance with each other. We measured the 2D:4D digit ratios (collected from both hands) and a personality trait known as dominance (measured with the Directiveness scale) in a sample of women attending a feminist conference. The sample exhibited significantly more masculine 2D:4D and higher dominance ratings than comparison samples representative of women in general, and these variables were furthermore positively correlated for both hands. The feminist paradox might thus to some extent be explained by biological differences between women in general and the activist women who formulate the feminist agenda.
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    • "Thus, our data support one of the outlined approaches, showing that women with rather masculine body traits also tend to have a higher number of sexual partners and start earlier with sexual activities, and have thus more unrestricted sexual behavior (Clark, 2004; Mikach and Bailey, 1999). On the other hand, we also supported the other possibility (Manning and Fink, 2008; Rahman et al., 2005), by showing that rather more feminine women have higher sociosexual desires. Sociosexual desires do not need to reflect behaviors (Penke and Asendorpf, 2008), but they can increase, for example, flirting behavior with men who are willing to provide immediate resources or status. "
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    • "reproductive success, pre-natal hormonal environment (reflected in 2D:4D value) seems to play a role as well. Variables associated with male fertility such as sperm number (Manning et al., 1998), sex drive, level of sexual excitement (Manning & Fink, 2008), number of sexual partners per individual (Honekopp et al., 2006) and age at first marriage (Sorokowski et al., 2012) were all related to 2D:4D. These results might suggest that digit ratio might be widely associated with traits related to male reproductive strategy. "
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