University of SheffieldWomen with high levels of neuroticism and more outgoing men are likely to give birth to a larger number of children in societies with usually high birth rates. The study was conducted by Dr Virpi Lummaa, from the University of Sheffield´s Department of Animal and Plant Sciences, Dr Alexandra Alvergne, from the Department of Anthropology, University College London and Markus Jokela from the University of Helsinki, Finland. They highlighted that the reproductive success of both men and women is influenced by their varying personality traits.

Scientists observed that new born’s physical condition was linked with maternal personality traits. Women with high neuroticism levels had children with decreased body mass index which may reflect malnutrition. In order to study the determinants of fertility patterns, personality traits are increasingly given emphasis. Personality traits are widely being studied to understand fertility patterns and how natural selection can help to maintain personality differences.

Previous analysis was conducted in modern Western population but the latest study was conducted between traditional masses. This enabled the team to examine how fertility rates in a natural environment were affected by personality. The experts accumulated information from four different villages in Senegal. They used the Big Five personality dimensions to analyze the personality effects of both partners on the number and health of their off-springs. The experts consider the Big Five personality dimensions to be the five fundamental personality traits present in humans.

Scientists observed that women with above-average levels of neuroticism were more prone to be anxious, depressive and moody. These women had 12 percent more children as compared to those with neuroticism below average. Women with higher social status were more inclined to this relationship. High neuroticism appears to carry a cost for the families and was a negative aspect of the link between maternal neuroticism and physical condition of the off-spring.

Dr Virpi Lummaa said: “Our results show that personality predicts family size differently in men and women, and those men with largest families have personality aspects different from the women with the largest families. Gaining understanding of such individual-level determinants of reproductive decisions helps in the current debate on the role of individual versus social factors in explaining recent fertility changes around the world.”

Similar investigations were conducted on men with above average levels of extraversion who were seemingly more social and outgoing. These men, it was observed that they had 14 percent more children than men with below average extraversion.

This study was published on 7 June 2010 in the Proceedings of the National Academy of Sciences.