Second to fourth digit ratio and facial asymmetry

Several studies have reported a positive association between degree of facial symmetry and attractiveness ratings, although the actual causes of the development of facial asymmetries remains to be confirmed. The current study hypothesizes that early hormone levels may play a crucial role in the development of facial asymmetries. Recent evidence suggests that the relative length of the second to fourth finger (2D:4D) is negatively related to prenatal testosterone and positively related to prenatal estrogen and may thus serve as a window to the prenatal hormonal environment. We measured 2D:4D in a sample of male and female college students and analysed their faces for horizontal asymmetries. 2D:4D was significantly negatively related to facial asymmetry in males, whereas in females facial asymmetry was significantly positively related to 2D:4D. We suggest that digit ratio may thus be considered as a pointer to an individual's developmental instability and stress through its association with prenatal sexual steroids.