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Sexual Dimorphism, Anxiety, Rhesus Macaques


In humans, administering androgens exogenously reduces anxiety. Because prenatal androgen exposure (PAE) has organizational effects on the brain, and because it is higher in males, this may explain why, on average, females are more likely than males to develop anxiety. To assess PAE, the pointer-to-ring-finger digit ratio (2D:4D ratio) is frequently used. Though this phenotype is sexually dimorphic across primate species, preliminary research in a small number of species indicates that PAE's effect on digit ratio may be in the opposite direction when comparing nonhuman primates and humans. in humans, males typically show lower 2D:4D ratios than do females, whereas in nonhuman primates, males exhibit a high 2D:4D ratio. We investigated whether this nonhuman primate digit ratio pattern is present in rhesus macaques (Macaca mulatta), and whether individual difference in 2D:4D ratio predicts infant anxiety. At 3-4 months of life, infant monkeys (n = 156) were separated from their mothers to assess temperament using a standardized test, the Human Intruder Paradigm. Subjects' 2D:4D ratios were measured between 3-17 years of age (M = 7.91). A t-test confirmed that teh 2D:4D ratio in rhesus monkeys is consistent with the nonhuman primate pattern, with males exhibiting a higher left-hand 2D:4D ratio than females (t(74) = -2.01, p = .049). Controlling for weight and sex, regressions revealed that lower right-hand 2D:4D ratio predicted infant anxiety (as measured by teeth grinding and yawns) (R = .39, p = .022), suggesting that higher PAE may mitigate threat-induced anxiety.


The Annual Mary Lou Fulton Mentored Research Conference showcases some of the best student research from the College of Family, Home, and Social Sciences. The mentored learning program encourages undergraduate students to participate in hands-on and practical research under the direction of a faculty member. Students create these posters as an aide in presenting the results of their research to the public, faculty, and their peers.

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Family, Home, and Social Sciences



Sexual Dimorphism in 2D:4D Digit Ratio is Linked to Anxiety in Rhesus Macaques (Macaca mulatta)

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