No Correlation Between 2D:4D Ratio and Environmental Sensitivity as a Personality Trait in Young Adults

Humans adaptively adjust their psychosocial phenotypes in response to a given early environment. Little is known about the associations between the factors at different levels that contribute to individual differences in developmental plasticity. To address this issue, the current study explored the associations between different levels of plasticity factors, prenatal androgen exposure, and personality traits related to environmental sensitivity. We recruited participants from Japan (184 females and 90 males, age range 18–23 years) and India (94 females and 86 males, age range 18–24 years) and measured their personality traits of environmental sensitivity and an indirect indicator of prenatal androgen exposure, the ratio of the length of the index (2nd digit: 2D) and ring (4th digit: 4D) fingers of their hands (i.e., 2D:4D). Overall, the analyses by country and sex did not reveal a clear correlation between the personality traits related to environmental sensitivity and 2D:4D ratios in any of the subsamples. Partially, the environmental sensitivity of Japanese females showed a weak positive correlation with the left- and two-handed mean 2D:4D ratios; however, this correlation approached zero when outliers were removed and reanalyzed. Finally, we address the reasons for the inconsistent findings regarding the associations between different levels of plasticity factors. Additionally, we highlight the remaining questions that should be addressed in the future.