male hand
Finger length indicates testosterone exposure in the womb and potentially, athletic abilities. Luc De Leeuw

Just by looking at your fingers, scientists can say if you are athletic. Their research also helps explain why men tend to perform better than women at spatial tasks.

Previous studies have shown that differences in finger length is a good indicator of whether a person has been exposed to high levels of testosterone in the womb or not. If the index finger is relatively short compared to the ring finger, this indicates that one has been exposed to a lot of testosterone in utero, whereas a relatively long index finger suggests a lower exposure to testosterone in the womb.

These different levels of exposure to testosterone before birth appear to have a significant impact on a variety of abilities in adulthood, including spatial abilities or athletic performances.

In the study published in Behavioural Brain Research, scientists have tested how exposure to testosterone improved women's abilities to complete spatial tasks to check if similar effects of the hormone could also be seen during adulthood.

Testosterone experiment

The scientists, from the Norwegian University of Science and Technology, measured the finger length of 42 women and gave half of them a dose of 0.5 mg of testosterone and the other half a placebo. Afterwards, the women had to solve different tasks such as navigating through a maze or mentally rotating different 3D objects.

The testosterone group had improved representations of the directions within the environment and performed significantly better on the mental rotation task compared to the placebo group, but navigation success and navigation strategy were similar in the two groups.

They discovered that the women who scored best on the mental rotation tasks were the ones thought to have been exposed to high levels of testosterone prenatally – with short index fingers compared to ring fingers – but also those who had been given testosterone in the experiment, as adults.

Testosterone and athletic abilities

The scientists also point out that this exposure to testosterone is also associated with people's athletic abilities.

"The greatest effect has been found for various physical and athletic measures, where high levels of prenatal testosterone are consistently linked with better capabilities," lead author Carl Pintzka says. "Beyond this we find a number of uncertain results, but a general feature is that high levels of testosterone generally correlate with superior abilities on tasks that men usually perform better, such as various spatial tasks like directional sense".

In contrast, low levels of testosterone – and a long index finger compared to the ring finger – are associated with better abilities in verbal memory tasks, such as remembering lists of words.