Digit Ratio (2D:4D) and Attachment Styles in Middle Childhood: Indirect Evidence for an Organizational Effect of Sex Hormones

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.