New study reveals finger length can indicate high testosterone levels

Concordia University investigation published in Personality and Individual Differences

Potential investors might wish to examine the fingers of their financial advisor prior to signing over any savings. A new study from Concordia University has found the length between the second and fourth finger is an indicator of high levels of prenatal testosterone, risk-taking and potential financial success in men. The findings, published in the journal of Personality and Individual Differences, suggest that alpha males may take greater risks in relationships, on the squash court and in the financial market.

"Previous studies have linked high testosterone levels with risky behaviour and financial success," says senior researcher Gad Saad, Concordia University Research Chair in Evolutionary Behavioral Sciences and Darwinian Consumption as well as a marketing professor at the John Molson School of Business. "We investigated the relationship between prenatal testosterone and various risk proclivities. Our findings show an association between high testosterone and risk-taking among males in three domains: recreational, social and financial."

"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.

Saad and his team analyzed risk-taking among 413 male and female students using a survey. "Prenatal testosterone exposure not only influences fetal brain development," adds 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 change in finger length produced by testosterone provides a handy measure of prenatal testosterone exposure. 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," says Professor Saad.