- During the study, factors such as male odor and face symmetry were also tested on a sample of women aged 18 to 34.
- Where many of the tests were inconclusive, the length of a man's ring finger produced unambiguous results.
- The longer the ring finger (compared with the shorter index), the greater the likely impact of testosterone.
The longer a man's fourth or ring finger is compared to his index finger, the more likely he is to be judged attractive by women, according to a study released Wednesday.
The results, published in the British Royal Society's journal Biological Sciences, unveil intricate links between foetal exposure of males to hormones, the development of certain physical traits, and what turns on the opposite sex.
It also adds to a growing body of research -- conducted under the banner of evolutionary psychology -- suggesting that the drivers of human behavior are found, more than previously suspected, in "nature" rather than "nurture."
Earlier studies had already shown that the size ratio between the fourth and second fingers, especially of the right hand, is a reliable indicator of the extent a man was exposed to testosterone while still in the womb.
The bigger the gap between a longer ring finger and a shorter index, the greater the likely impact of the hormone.
For the new study, scientists led by Camille Ferdenzi of the University of Geneva designed an experiment to find out if women are drawn to the telltale signs of high testosterone levels in men -- a symmetrical face, a deeper voice, a particular body odor -- who have this more "masculine" finger configuration.
More than 80 women university students between 18 and 34 looked at pictures of 49 similarly aged men, and were asked to evaluate them for masculinity and attractiveness.
Smaller groups of women listened to recordings of the male voices, and smelled samples of their body odor, taken from cotton pads worn under the arm for 24 hours.