Journal of Undergraduate Research


prenatal androgens, dominance rank, rhesus monkeys


Family, Home, and Social Sciences




Prenatally, androgens are responsible for masculinizing the developing male fetus. Prenatal androgen exposure (PAE) also shapes male brain functioning and organization, and is the main underlying influence underlying sexually dimorphism, to a certain extent even in adulthood. Through its effect on the brain, PAE can influence personality and behavior, likely contributing to gross sex differences in these traits, as well as within-sex variation (see Manning, 2011). One of the most commonly used biomarkers used to study PAE is the second-to-fourth-finger length ratio (2D:4D ratio). In humans, males tend to have a longer ring finger and shorter pointer finger (i.e., a 2D:4D ratio < 1), whereas females tend to have a longer pointer finger and shorter ring finger (i.e., a 2D:4D ratio ≥ 1). This sex difference is likely due to a higher concentration of androgen receptors in the ring finger relative to the pointer finger (Zheng & Cohn, 2010). Consequently, when testes produce androgens and masculinize the male fetus, the androgen receptors in the ring finger induce greater growth in the ring finger of males, compared to females. Research using 2D:4D research shows that in humans, low (i.e., male-typical) 2D:4D ratio is linked with variation in a variety of personality traits, including aggression, competitiveness, and temperament traits important to social dominance (see Manning, 2011).

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