Have a good look at your partner's fingers during the ring ceremony as men with short index fingers and long ring fingers are nicer towards women, says a study.
This unexpected phenomenon stems from the hormones these men have been exposed to in their mother's womb, say researchers from McGill University. The findings may also help explain why these men tend to have more children.
"It is fascinating to see that moderate variations of hormones before birth can actually influence adult behaviour in a selective way," said Simon Young, McGill Emeritus Professor in psychiatry and co-author of the study.
The study shows a link between a biological event in foetal life and adult behaviour. Men's index fingers are generally shorter than their ring fingers and this difference is less pronounced in women.
Previous research has found that digit ratio - defined as the second digit length divided by the fourth digit length - is an indication of the amount of male hormones (mainly testosterone) that someone has been exposed to as a foetus.
The smaller the ratio, the more male hormones. The study suggests that this has an impact on how grown up men behave especially with women.
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"When with women, men with smaller ratios were more likely to listen attentively, smile and laugh, compromise or compliment the other person," said Debbie Moskowitz, lead author and professor of psychology.
These men were also less quarrelsome with women than with men, whereas the men with larger ratios were equally quarrelsome with both.
Although for women, digit ratio variation failed to predict their behaviour, researchers said.
"Our research suggests these men have more harmonious relationships with women. This might explain why they have more children on average", the authors said.
The research appeared in the journal Personality and Individual Differences.