Spouses don't grow alike, they start alike

EAST LANSING, Mich., Aug. 31 (UPI) -- Married couples do not grow more alike, they are attracted to each other when they meet because they are more alike, U.S. researchers say.

Lead investigator Mikhila Humbad, a doctoral candidate in clinical psychology, of Michigan State University in East Lansing, Mich., says the study shows people tend to pick their spouse based on shared personality traits.

"Existing research shows that spouses are more similar than random people," Humbad says in a statement. "This could reflect spouses' influence on each other over time, or this could be what attracted them to each other in the first place. Our goal in conducting this study was to help resolve this debate."

Humbad and colleagues analyzed data on 1,296 married couples from the Minnesota Center for Twin and Family Research for personality characteristics.

The study, published in the journal Personality and Individual Differences, finds in most cases the couples did not become more alike with more years of marriage -- concluding spousal similarity is better explained by selection than gradual convergence.

The one personality characteristic that doesn't meet this pattern is aggression, Humbad says.

"It makes sense if you think about it," Humbad says. "If one person is violent, the other person may respond in a similar fashion and thus become more aggressive over time."