Men with a smaller index (pointer) finger to ring finger ratio tend to be kinder toward women; this nicer behavior stems from being exposed to lower levels of male hormones, particularly testosterone, in the womb, according to a new study by researchers at McGill University. The findings might shed light on why these men tend to have more children.
“It is fascinating to see that moderate variations of hormones before birth can actually influence adult behavior in a selective way,” says study coauthor Simon Young, a McGill Emeritus Professor in Psychiatry.
Prior research has found that the finger digit ratio (the second digit length divided by the fourth digit length) is an indication of the levels of male hormones, mainly testosterone, that a person was exposed to as a fetus: the smaller the ratio, the more male hormones. The McGill study suggests that this has an impact on how adult men behave, particularly toward women.
Many studies have been conducted in an attempt to determine the impact of digit ratio on adult behavior. This study, however, is the first to show how finger length affects behavior toward either males or females.
“When with women, men with smaller ratios were more likely to listen attentively, smile and laugh, compromise or compliment the other person,” says Debbie Moskowitz, lead author and Professor of Psychology at McGill.
Men with smaller finger ratios 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, however, digit ratio variation did not seem to predict how they behaved, the researchers report.
For the study, 155 participants filled out forms for every social interaction that lasted five minutes or more during the last 20 days; they also checked off a list of behaviors they engaged in. Based on previous research, the scientists classified the behaviors as agreeable or quarrelsome.
Men with small digit ratios reported approximately one-third more agreeable behaviors and one-third fewer quarrelsome behaviors than men with large digit ratios.
An earlier study also found that men with smaller digit ratios have more children. “Our research suggests they have more harmonious relationships with women; these behaviors support the formation and maintenance of relationships with women,” Moskowitz says. “This might explain why they have more children on average.”
The researchers were surprised to find no statistically relevant connection between finger ratios and dominant behaviors. They suggest future research could investigate specific situations where male dominance varies — such as competitive situations with other men — to see if a link can be found.
The study is published in the journal Personality and Individual Differences.
Source: McGill University