A team of researchers at Concordia University analyzed risk-taking among 413 male and female students.  The findings were published in Personality and Individual Differences journal.   

“Prenatal testosterone exposure not only influences fetal brain development,” said study co-author and graduate student, Zack Mendenhall, “but it also slows the growth of the index finger relative to the sum of the four fingers excluding the thumb.”

The study compared the length of the index finger with all four digits (known as the rel2 ratio) and found that those with lower ratios were more likely to engage in risk-taking. These findings were further confirmed by the additional measurement of the ratio between the index and ring finger. These correlations were only observed in men.

“A possible explanation for the null effects in women is that they do not engage in risky behaviour as a mating signal, whereas men do,” said Professor Gad Saad, Concordia University Research Chair in Evolutionary Behavioral Sciences and Darwinian Consumption.   

“Since women tend to be attracted to men who are fit, assertive and rich, men are apt to take risks with sports, people and money to be attractive to potential mates. What’s interesting is that this tendency is influenced by testosterone exposure – more testosterone in the womb can lead to more risks in the rink, the bar and the trading floor in later in life,” says first author and Concordia doctoral student, Eric Stenstrom.