Assortative Mating and Digit Ratio (2D:4D): A Pre-Registered Empirical Study and Meta-Analysis

Richards, Gareth and Baron-Cohen, Simon and van Steen, Tommy and Galvin, John (2020) Assortative Mating and Digit Ratio (2D:4D): A Pre-Registered Empirical Study and Meta-Analysis. Early Human Development. ISSN 0378-3782

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Abstract

Background: It has been hypothesised that the ratio of length between the second and fourth fingers (2D:4D), commonly employed as an indicator of foetal sex hormone exposure, may be positively correlated between heterosexual partners.
Aims: As previous evidence has been conflicting, our study aimed to determine whether intra-couple correlations exist for digit ratio variables, and if so, to estimate the size and direction of these effects.
Study design: We present a preregistered (osf.io/6jg8p) correlational study and quantitative meta-analysis of the available literature, and attempted to locate further published and unpublished data (i.e. ‘grey literature’) by contacting n=244 researchers in the 2D:4D and related fields.
Subjects: n=58 heterosexual dating couples from the UK took part in our empirical study, and the meta-analysis included data from k=11 samples.
Outcome measures: We measured digit ratio for the right hand (R2D:4D), left hand (L2D:4D), and average of both hands (M2D:4D), as well as the right-left-difference (D[R-L]).
Results: We found no evidence of significant positive intra-couple correlations in our own data, but a significant (positive) meta-analytic effect size estimate emerged for R2D:4D (r=0.072, p=0.014). The meta-analytic effects for L2D:4D (r=0.043, p=0.303), M2D:4D (r=0.070, p=0.225), and D[R-L] (r=0.028, p=0.649) were all in the same direction but not statistically significant. However, if the sample from Klimek et al. (2014, 2016) were omitted, meta-analysis would also yield a significant positive correlation for M2D:4D (r=0.128, p=0.001).
Conclusions: Although our findings are based on a fairly small range of studies, which themselves provide a relatively small sample of participants, they do imply the intriguing possibility of small effects of positive assortment in relation to characteristics associated with the prenatal hormonal environment.

Item Type: Article
Identification Number: https://doi.org/10.1016/j.earlhumdev.2020.105159
Date: 20 August 2020
Uncontrolled Keywords: 2D:4D; Assortative mating; Behavioral genetics; Digit ratio; Fetal testosterone; Mate choice; Meta-analysis
Subjects: C800 Psychology
Divisions: Faculty of Business, Law and Social Sciences > School of Social Sciences > Dept. Psychology
Depositing User: Galvin
Date Deposited: 04 Sep 2020 13:56
Last Modified: 05 Sep 2020 11:13
URI: http://www.open-access.bcu.ac.uk/id/eprint/9740

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