The development of sex differences in digital formula from infancy in the Fels Longitudinal Study. Proceedings of the Royal Society B, 272, 1473-1479

Department of Anthropology, Harvard University, Peabody Museum, 11 Divinity Avenue, Cambridge, MA 02138, USA.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 08/2005; 272(1571):1473-9. DOI: 10.1098/rspb.2005.3100
Source: PubMed


Relative finger lengths, especially the second-to-fourth finger length ratio, have been proposed as useful markers for prenatal testosterone action. This claim partly depends on an association of relative finger lengths in adults with related sex differences in children and infants. This paper reports the results of a study using serial radiographs to test for both sex differences in the fingers of infants and children and for a relationship between sex differences in the children and infant finger and adult finger length ratios. This is the first study using long-term serial data to evaluate the validity of finger length ratios as markers. We found not only that sex differences in finger length ratios arise prior to puberty, but that sex differences in the fingers of children are highly correlated with adult finger length ratios. Our results strongly encourage the further use of finger length ratios as markers of perinatal testosterone action.

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Available from: Ellen Demerath, May 07, 2015
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    • "The small but reliable association between relative finger length and prenatal androgen/estrogen balance makes the digit ratio a viable biomarker for early exposure to sex hormones. The gold standard for digit ratio measurement is based on bone length estimation from X-rays, CT scans, or similar methods (e.g., McIntyre et al. 2005); however, most studies in humans measure digit ratios indirectly on the skin surface, either with a caliper or from hand scans or photocopies. While indirect methods are considerably more practical, they increase the measurement error associated with 2D:4D estimation and further weaken the correlation with early hormonal exposure. "
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    ABSTRACT: Sex differences in attachment are absent during infancy and early childhood, emerge in middle childhood with self-reports and doll-play tasks, and persist into adulthood, when they are most reliably detected in romantic attachment styles. In our previous work, we hypothesized that sex differences in attachment develop under the influence of adrenal androgens during the transition form early to middle childhood, following activation of hormone-sensitive neural pathways organized by prenatal and early postnatal exposure to sex hormones. In this study we tested the association between the right-hand 2D:4D digit ratio (a marker of early exposure to androgens and estrogen) and sexually differentiated dimensions of attachment in middle childhood assessed with the Coping Strategies Questionnaire (CSQ). In a sample of 285 Italian children aged 8–10 years, females scored lower in avoidance and higher in preoccupation, while no significant sex differences were observed in felt security. Consistent with our predictions, higher (feminized) digit ratios were significantly associated with lower avoidance and higher preoccupation scores in both males and females. In contrast, there was no significant association between digit ratio and felt security in either sex. These results corroborate the hypothesis that sex differences in attachment reflect the activation of sexually differentiated pathways organized in early development, and for the first time implicate sex hormones in the development of individual differences in attachment styles.
    Full-text · Article · Jan 2016
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    • "Also, the conclusion of stability from young childhood reported by Manning et al. (1998) may have obscured instability across a narrower time frame as it relied on a regression analysis spanning the ages 2 to 25 years. In a longitudinal study of radiographed 2D:4Dl, the sex difference in 2D:4D was not significant until age 9 years (McIntyre et al., 2005), and the ratio has been reported to increase with age in both sexes from age one until at least age 17 years (McIntyre et al., 2005; Trivers et al., 2006). A recent study of 0-, 12-and 24-month-old infants also found some temporal correlations in 2D:4D (r = .35 "
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    ABSTRACT: The popularity of using the ratio of the second to the fourth digit (2D:4D) to study influences of early androgen exposure on human behavior relies, in part, on a report that the ratio is sex-dimorphic and stable from age 2years (Manning et al., 1998). However, subsequent research has rarely replicated this finding. Moreover, although 2D:4D has been correlated with many behaviors, these correlations are often inconsistent. Young children's 2D:4D-behavior correlations may be more consistent than those of older individuals, because young children have experienced fewer postnatal influences. To evaluate the usefulness of 2D:4D as a biomarker of prenatal androgen exposure in studies of 2D:4D-behavior correlations, we assessed its sex difference, temporal stability, and behavioral correlates over a 6- to 8-month period in 126, 2- to 3-year-old children, providing a rare same-sample replicability test. We found a moderate sex difference on both hands and high temporal stability. However, between-sex overlap and within-sex variability were also large. Only 3 of 24 correlations with sex-typed behaviors-scores on the Preschool Activities Inventory (PSAI), preference for a boy-typical toy, preference for a girl-typical toy, were significant and in the predicted direction, all of which involved the PSAI, partially confirming findings from another study. Correlation coefficients were larger for behaviors that showed larger sex differences. But, as in older samples, the overall pattern showed inconsistency across time, sex, and hand. Therefore, although sex-dimorphic and stable, 2D:4D-behavior correlations are no more consistent for young children than for older samples. Theoretical and methodological implications are discussed.
    Full-text · Article · Nov 2015 · Hormones and Behavior
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    • "Digit ratio has also been related to physical aggression, although the evidence for a link is equivocal. Some studies reported negative correlations between 2D:4D and physical aggression in men, but not in women (Bailey and Hurd, 2005; Butovskaya et al., 2010b; Hurd et al., 2010; McIntyre et al., 2005), whereas other studies found no correlation of 2D:4D with aggression (Austin et al., 2002; Butovskaya et al., 2007; H€ onekopp and Watson, 2011). "
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    ABSTRACT: Digit ratio (2D:4D)-a putative marker of prenatal androgen activity-has been shown to correlate with self-reported physical aggression and dominance behavior, especially in male children and adolescents. This evidence is derived primarily from the study of Western samples. Digit ratios, self-reported aggression, and dominance behavior were collected from men and women in two traditional, small-scale societies, i.e., the Hadza and the Datoga of Tanzania. We found significant differences in physical and verbal aggression, anger, and hostility between the two societies with the Datoga reporting higher scores on all four measures. Moreover, self-reported dominance in the Datoga was higher than in the Hadza. The Datoga showed lower left and right hand 2D:4D ratios than the Hadza. Men reported higher physical and verbal aggression and dominance, and had lower 2D:4D ratios than women. A significant negative association between 2D:4D and dominance was found in Hadza women. We discuss our findings with reference to differences in mating systems between the two small-scale societies and previous findings of Western and other small-scale societies. Am. J. Hum. Biol., 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    Full-text · Article · Mar 2015 · American Journal of Human Biology
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