A new means of measuring index/ring finger (2D:4D) ratio and its association with gender and hand preference.

Relative finger length can predict a person's gender or their hand preference. We measured finger length using a new "tubes" test, which required participants to slide a clear plastic tube over their fingers and read the length from an attached mm scale. Data collected from 600 students demonstrated that the right fingers are longer than the left for dextrals, but not for non-dextrals. Examination of the relative length of the index and ring fingers revealed a clear gender effect. There was also an effect of hand preference on index/ring finger ratio whereby non-dextrals showed a more masculine pattern compared to dextrals. For non-dextrals, prenatal exposure to high testosterone levels may have caused both a shift away from dextrality and a more masculine pattern of finger ratio. In the second experiment, finger length was measured by the tubes test and by photocopying the hands in 124 undergraduates. The tubes test yielded a longer estimate of ring finger length compared to the photocopy method. Despite this, there was a strong correlation between the tests and both showed an association with gender. Finally, test-retest scores for 45 participants showed a high level of reliability for absolute and relative finger measures. We conclude that the tubes technique provides an effective and easy-to-use means of measuring finger length, which can be administered in a classroom setting.