Born leaders may be more likely to have children than people who prefer to be led, a study suggests.

Researchers found that among Finnish adults in a long- term health study, those who'd scored high on a "leadership" scale as teenagers were more likely than low scorers to have a child by the age of 39.

In contrast, several other aspects of the "type A" personality — aggressiveness, eagerness and a strong sense of responsibility — were unrelated to fertility.

The findings suggest that something about leadership traits, specifically, affects a person's likelihood of having children, the researchers report in the Journal of Personality.

It's possible that leadership is expressed not only as a drive for achievement on the social level, but also on the family level, explained lead researcher Dr. Markus Jokela, of the University of Helsinki.

"That is, status-striving and fertility may share, to some extent at least, a common psychological background," he told Reuters Health.

The link between higher social rank and reproductive success is seen in almost all non-human animals that have a social hierarchy, Jokela noted.

For people, the decision to have children is obviously complex. Still, Jokela said, "the leadership-fertility association suggests that this effect may still work in humans at the level of personality differences.

"The findings are based on 1,313 adults followed since 1980. Each underwent a standard personality assessment at some point between the ages of 12 and 21. Leadership was gauged by the extent to which participants agreed with statements like "I always take charge of things" and "I like to tell others what to do."

In general, Jokela's team found, the odds of having a child by age 39 increased in tandem with adolescent leadership scores. For each standard step above the average, the odds of having a child increased by 11 percent for men and 19 percent for women. The link was not explained by higher education levels or higher marriage rates among leaders.

According to Jokela, the findings lend insight into the "psychology of childbearing" — a subject that has so far been little studied.

However, the leadership-fertility relationship might look different depending on the society, he pointed out. For example, in a society where women "have to make a big tradeoff" between career-building and family-building, strong leadership traits might be linked to lower fertility.

"Apparently," Jokela said, "Finnish women with high leadership personality manage to do both."

SOURCE: Journal of Personality, February 2009.