CANADA (KRON) — When it comes to finding out what a man might be hiding, look at his fingers. Guys with short index fingers are nicer to women.

Researchers at McGill University in Canada studied finger sizes in men and the results show a link in how men behave towards women. This is the first study to show this kind of connection, researchers say.

The study found that men whose index finger was smaller than their ring finger were more likely to smile and laugh, compromise or compliment women. On the other hand, those with larger index fingers exhibited a more contentious nature.

“It is fascinating to see that moderate variations of hormones before birth can actually influence adult behavior in a selective way,” Simon Young, a McGill Emeritus Professor in Psychiatry and coauthor of the study, said.

Researchers say that the link stems from the hormones these men have been exposed to while in the womb. The findings also reveal that these same men have more children.

“Our research suggests they have more harmonious relationships with women; these behaviors support the formation and maintenance of relationships with women,” says Debbie Moskowitz, lead author and Professor of Psychology at McGill. “This might explain why they have more children on average.”

“When with women, men with smaller ratios were more likely to listen attentively, smile and laugh, compromise or compliment the other person,” says Moskowitz. They acted that way in sexual relationships, but also with female friends or colleagues. These men were also less quarrelsome with women than with men, whereas the men with larger ratios were equally quarrelsome with both. For women though, digit ratio variation did not seem to predict how they behaved, the researchers report.