The digit ratio (2D:4D) and economic preferences: no robust associations in a sample of 330 women

Investigating the effects of prenatal testosterone exposure (via 2D:4D) and socio-relational factors on 3-6-year-old preschoolers' prosocial choices

BACKGROUND AND AIMS

Prosocial behavior such as helping and sharing develops early in childhood. Yet very few studies have investigated physiological and relational factors shaping prosociality among children. Here, we systematically examined the role of prenatal androgen exposure alongside prestige, dominance, and friendship in 3-6-year-old preschoolers' prosocial sharing with familiar peers.

METHODS

We tested a sample of 65 children, predominately of European descent. We used a cost-free direct-interaction prosocial choice task to assess children's prosocial tendencies. Second-to-fourth digit ratio (2D:4D) was used as a retrospective biomarker for prenatal androgen exposure. Prestige was measured through behavioral observations of interaction partners and visual regard, dominance through teacher questionnaires, and friendship via peer preference assessments.

RESULTS

We found that children acted prosocially when tested with a familiar peer. Children with lower 2D:4D (higher prenatal androgen exposure) behaved more prosocially. Further, there were marginal associations between the donors' prosocial tendencies and their visual regard as a proxy of their prestige (positive effect) and their teacher-rated dominance relative to the recipient (negative effect). Neither age, sex, nor friendship influenced prosocial choices.

CONCLUSIONS

Prenatal androgen exposure, approximated via 2D:4D, was associated with prosocial behavior. In contrast to previous research in older children, higher exposure was related to stronger prosocial tendencies, which corresponds to earlier findings on fairness in adults. Our findings point towards a potential role of sex steroids in the early development of children's social behavior, but they have to be interpreted with caution due to the small sample size of the current study. Nevertheless, they underscore the importance of integrating biological and psychological perspectives, while also highlighting the significance of studying the development of prosocial behavior within peer groups.

Born to be wild: Second-to-fourth digit length ratio and risk preferences

The second-to-fourth digit length ratio of an individual's hand (digit ratio) is a putative biomarker for prenatal exposure to testosterone. We examine the hypothesized negative association between the digit ratio and the preference for risk taking within a large U.S. population survey. Our statistical framework provides a cardinal proxy for the true digit ratio based on ordinal digit ratio measurements and accounts for measurement error under the assumptions of Gaussianity and time-invariant true digit ratios. Our empirical findings support the hypothesis and suggest a meaningful biological basis for risk preferences.

In and out of unemployment-Labour market transitions and the role of testosterone

Biological processes have provided new insights into diverging labour market trajectories. This paper uses population variation in testosterone levels to explain transition probabilities into and out of unemployment. We examine labour market transitions for 2004 initially employed and 111 initially unemployed British men from the UK Household Longitudinal Study ("Understanding Society") between 2011 and 2013. We address the endogeneity of testosterone levels by using genetic variation as instrumental variables (Mendelian Randomization). We find that for both initially unemployed men as well as initially employed men, higher testosterone levels reduce the risk of unemployment. Based on previous studies and descriptive evidence, we argue that these effects are likely driven by differences in cognitive and non-cognitive skills as well as job search behaviour of men with higher testosterone levels. Our findings suggest that latent biological processes can affect job search behaviour and labour market outcomes without necessarily relating to illness and disability.

Overclaiming is not related to dark triad personality traits or stated and revealed risk preferences

The tendency to be overly confident in one’s future and skills has long been studied. More recently, a correlate of this overconfidence, the tendency to overclaim knowledge, has been in the focus of research. Its antecedents and downstream behavioral consequences are still in question. In a sample of undergraduate students (N = 168), we tested whether a set of characteristics of the person (e.g., age, gender) and personality traits (i.e., the Dark Triad) is related to overclaiming knowledge. Moreover, we investigated whether overclaiming, in turn, predicts risk preferences. To this end, we asked individuals to rate their confidence in solving a set of different math problems and their familiarity with a set of math concepts. Some of these concepts were nonexistent, thereby allowing participants to overclaim knowledge. Participants then stated their general risk preference and performed three tasks revealing their general, financial, and social risk preferences. We demonstrated the hypothesized relationship between overclaiming and confidence. Furthermore, we observed that the assessed characteristics of the person were not correlated with overclaiming. If anything, height and digit ratio, a phenomenological correlate of hormonal differences during development, tended to be associated with overclaiming. Surprisingly, overclaiming was not at all related to risk preferences or personality traits. This set of results shows the need for relevant theoretical and methodological refinements.

Do sex hormones at birth predict later-life economic preferences? Evidence from a pregnancy birth cohort study

Economic preferences may be shaped by exposure to sex hormones around birth. Prior studies of economic preferences and numerous other phenotypic characteristics use digit ratios (2D : 4D), a purported proxy for prenatal testosterone exposure, whose validity has recently been questioned. We use direct measures of neonatal sex hormones (testosterone and oestrogen), measured from umbilical cord blood (n = 200) to investigate their association with later-life economic preferences (risk preferences, competitiveness, time preferences and social preferences) in an Australian cohort (Raine Study Gen2). We find no significant associations between testosterone at birth and preferences, except for competitiveness, where the effect runs opposite to the expected direction. Point estimates are between 0.05-0.09 percentage points (pp) and 0.003-0.14 s.d. We similarly find no significant associations between 2D : 4D and preferences (n = 533, point estimates 0.003-0.02 pp and 0.001-0.06 s.d.). Our sample size allows detecting effects larger than 0.11 pp or 0.22 s.d. for testosterone at birth, and 0.07 pp or 0.14 s.d. for 2D : 4D (α = 0.05 and power = 0.90). Equivalence tests show that most effects are unlikely to be larger than these bounds. Our results suggest a reinterpretation of prior findings relating 2D : 4D to economic preferences, and highlight the importance of future large-sample studies that permit detection of small effects.