June 11, 2010 at 9:27 AM ETAre you that guy who circulates at a party, then suggests a spontaneous road trip to Vegas where you proceed to chat up every woman around the pool? Well, if one of those women happens to be a little neurotic, you, my gregarious friend, may have hit the baby-making daily double. In a study released this week in Proceedings of the National Academy of Sciences, scientists who studied a population in Senegal found that extroverted men and neurotic -- needy, anxious, depressed -- women made more babies. Research in this field is still sketchy, but those results sort of gibe with the findings of studies conducted in modern industrial societies. I say “sort of” because there are two important differences. First, the people in Senegal practice polygamy, and second, they don’t generally use contraception. But just like this one, the work done in modern societies shows that extroverted men are richer, and we all know how much more sex you can have if you’re, oh, a rich golfer. In Senegal, you can have more wives, too. As Professor Virpi Lummaa of the U.K.’s Sheffield University, one of the study authors, explained to me, the findings suggest “that the link between extroversion and number of children in men is driven by the effects of extroversion on the probability of belonging to the high social class.” Since other studies in “low fertility” countries like the U.S. and Europe, where birth control is common, confirm the link, she believes these “effects might be universal across different societies.” As for the women, she said, previous research showed that neurotic women in places like the U.S. and Europe have what amounts to daddy issues (Lummaa called it “attachment anxiety”) and so are highly motivated to have sex. Lots of sex means more babies, if you aren’t using birth control. Another possibility, Lummaa told me, is that in a polygamous society, neurotic women want to “outcompete their co-wives” in the baby-making race. The neurotic women do pay a price: children of highly neurotic women were more likely to be undernourished. Isn’t it possible, though, that having all those kids could make any woman neurotic? Maybe, but, the paper argued, “the fact that neuroticism does not increase with age, whereas the number of children does, also suggests that, in this population, neuroticism is more likely to be responsible for, rather than a consequence of, differential reproduction.” Have you seen this phenomenon in your own life? Tell us in the comments.To read more Body Odd posts, click here. You can also follow us on Twitter at http://twitter.com/bodyodd.