S. Alexandra Burt, a behavioral geneticist at Michigan State University, said her study, published in the Archives of General Psychiatry, analyzed data from 289 pairs of twins, focusing on marriage and anti-social behavior, the Lansing (Mich.) State-Journal reported Monday.
"Nicer guys are more likely to get married," she said, "and, once they get married, they appear to get even nicer, in the sense of a reduction in anti-social behavior."
Burt said her study found the men who displayed the fewest anti-social behaviors between the ages of 17 and 20 were more likely to be married by the age of 29.
The researcher said she does not know why marriage tended to mellow the men, but she has some ideas.
"One is what's called decreased association with deviant peers," she said. "If you're married and spending lots of time with your wife, you're probably not spending time with your rowdy friends, who might be more likely to encourage you to go out and get in trouble."