FRIDAY, March 25 (HealthDay News) -- Canadian researchers say they've found a way to help 'finger' men with physically aggressive personalities.

A University of Alberta study finds that measuring a man's index finger length relative to his ring finger length predicts his predisposition to being physically aggressive.

The shorter the index finger relative to the ring finger, the higher the amount of prenatal testosterone and the more likely the man will be physically aggressive, they researchers say.

In a prepared statement, study co-author Dr. Peter Hurd admitted he initially thought the finger-aggression link was "a pile of hooey," until he reviewed the data.

According to the researchers, experts have known for a hundred years that the index-to-ring finger length ratio of men differs considerably from that seen in women. And more recently, research has suggested that the length of men's fingers changes depending on their exposure to testosterone in the womb.

Now, finger length and physical aggression seem to be linked as well, at least in men. The Alberta team found no such link in women.

"More than anything, I think the findings reinforce and underlie that a large part of our personalities and our traits are determined while we're still in the womb," Hurd said.

The study, reported in the March issue of Biological Psychology, found no correlation between finger lengths and non-physical forms of aggression, such as verbal aggression or angry or hostile behavior. Hurd said he is continuing his research on physical aggression, however, by comparing hockey players' finger lengths to the number of penalty minutes they rack up in a given season.

In another study, to be published later this year, Hurd found that men with more "feminine" finger ratios tended to be more prone to depression.

He stressed that "finger lengths explain about 5 percent of the variation in these personality measures, so research like this won't allow you to draw conclusions about specific people. For example, you wouldn't want to screen people for certain jobs based on their finger lengths."

"But finger length can tell you a little bit about where personality comes from, and that's what we are continuing to explore," he said.

More information

The American Academy of Pediatrics has information about aggressive behavior in children.