Abstract
Objectives: The purpose of the present study was to investigate the ratio of the length of the second digit (index finger) to
the length of the fourth digit (ring finger) and its association with gender role identity in a general sample of Japanese young
adults.
Method: The lengths of second digit and fourth digit of the right hand of 380 students (216 men and 164 women) having a
mean age of 20.6 years (SD＝1.5) were measured at a Japanese university, while the left-hand data were obtained from 45 men
and 30 women. In addition, these participants also responded voluntarily to a survey questionnaire measuring gender role
identity. The second digit to fourth digit ratios were compared between men and women, and their association with gender
role identity were examined.
Results: The right hand second digit to fourth digit ratio in women was significantly higher than that in men, whereas left hand
ratios were comparable between men and women. Men scored significantly higher on masculinity than women, but femininity
scores were comparable between men and women. In men, neither the right hand nor left hand ratio correlated significantly
with masculinity or femininity. Similarly, in women, the right hand second digit to fourth digit ratio was not correlated with
either scale but the left hand ratio was correlated significantly with masculinity; this correlation should however be interpreted
with caution due to extremely limited sampling.
Conclusion: The right hand second digit to fourth digit ratio is a sexual dimorphic parameter, but its association with gender
role identity could not be evident in a general sample of Japanese young adults.
