• The researchers analysed previously collected answers from 575 North American and British people on a standardized questionnaire which assesses an individual's attitudes and desires towards 'non-committal' sex. They also looked at photocopies of the right hand from 1,314 British men and women.
  • From these photocopies, they measured the length of the index (second) finger and the ring (fourth) finger. The shorter the index finger in relation to the ring finger (the 2D:4D ratio), the higher the levels of testosterone that person is likely to have been exposed to while developing in the womb. This is true for both men and women.
  • From previous work, the researchers already knew that the higher levels of foetal testosterone can go together with greater sexual promiscuity as an adult. While not predictive of individual behaviour, the length of the ring finger versus the index finger can help identify the group of people who are more likely to be promiscuous.

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