For women in Senegal, it pays to be (a little) neurotic

By Kate Shaw

Is there a prime personality for reproduction? A new study in PNAS investigates the links between personality and reproductive success in Senegalese men and women. In the four rural communities where the study was conducted, polygyny is commonplace, families have many children, and mortality is very high. These conditions are thought to be similar to those in humans’ distant past, so the authors believe that the selective processes at work here may mimic those that have acted on personality traits over our evolutionary history.

To assess extraversion and neuroticism, 64 husbands and their wives were given a 27-question personality assessment. The body mass index (BMI) and mid upper arm circumference (MUAC) were measured for children in each family, providing an approximation of their physical health and well-being. On average, each female had 5 children.

Neurotic women—those who were frequently anxious, depressive, and/or moody—had 12 percent more children than women scoring low on the neuroticism spectrum. However, these children tended to be less healthy, on average, than the children of less neurotic women. Especially in the lowest social class, kids born to neurotic women had lower BMIs and MUACs than those born to more relaxed moms, suggesting poorer health and a lower probability of survival. Overall, females with intermediate neuroticism ratings enjoyed the greatest reproductive success, indicating that natural selection is working against ladies on either end of the spectrum.

The results for males were more straightforward: extraverted men tended to have more children than shyer men did. However, this effect was confounded by two other characteristics; extraverted men were more likely to belong to a high socio-economic class and to engage in polygyny, increasing their chances to father an army of kids. Among males, there was no effect of neuroticism on either the quality or quantity of children, and extraversion didn’t affect either measure of reproductive success in females.

These results differ from those of previous studies, which show that, in industrialized nations, high neuroticism in females is correlated with a smaller number of children. The authors suggest that, in cultures where men have multiple wives, neurotic women may be particularly likely to be jealous of her husband's other wives and try to outcompete them by bearing more children.