New study finds conscientiousness linked to higher reproductive success worldwide

A new study published in Evolutionary Psychology finds that personality trait conscientiousness—the tendency to be organized, responsible, self-disciplined, and goal-oriented—is consistently linked to having more children across cultures, suggesting it may be favored by natural selection.

Researchers understand that personality traits are influenced by both genetics and behavior, making them potential targets for natural selection. According to evolutionary theory, traits positively linked to reproductive success should become more common over time. Previous research has shown mixed results regarding how the “Big Five” personality traits (extraversion, neuroticism, agreeableness, conscientiousness, and openness) relate to having children, with findings often varying by cultural context.

While prior studies have generally found positive links between extraversion and having more children, and negative associations between neuroticism and reproductive success, evidence for the other three traits has been inconsistent. This raises important questions about whether these traits are under selective pressures and if these pressures might vary across different environments.

To address these questions, Janko Međedović examined data from the World Values Survey, which provided them with an exceptionally large and diverse sample spanning 17 countries. Their goal was to determine how the Big Five traits relate to reproductive success globally and whether these relationships differ based on cultural context.

Drawing from Wave 6 of the World Values Survey (2010-2012), Međedović analyzed data from 22,635 participants (51% female, average age approximately 42 years). Personality was measured using a shortened version of the Big Five Inventory, with two questions per trait except for openness, which was assessed with a single item due to translational issues. Reproductive success was measured simply as the self-reported number of biological children.

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Initial correlations showed small but significant associations: conscientiousness was positively related to having more children, while extraversion, neuroticism, and openness showed negative associations. After controlling for demographic variables like age, sex, education, and social class, conscientiousness emerged as the only trait consistently linked to greater reproductive success across the overall sample.

Interestingly, Međedović discovered a nonlinear relationship between openness and fertility: individuals with above-average openness had significantly fewer children, while those with low or average openness had similar (and higher) reproductive success. This pattern suggests a threshold-like effect rather than a simple linear trend and may reflect selection pressures acting specifically against high levels of openness.

Perhaps most notable was the finding that the relationship between personality and reproductive outcomes varied significantly across countries. Traits like neuroticism, extraversion, and openness showed both positive and negative associations depending on the cultural context. For example, extraversion was positively associated with fertility in some countries (like Thailand), but negatively associated in others (such as Algeria and Tunisia). Similarly, neuroticism showed a negative association in Yemen but a positive one in Iraq.

In contrast, conscientiousness stood out as the most consistently selected-for trait across countries. Wherever a significant association was found between conscientiousness and number of children, the relationship was always positive. This pattern suggests that conscientiousness may be under uniform directional selection across diverse populations, likely due to its alignment with traits that facilitate long-term planning, goal pursuit, and relationship commitment—factors that may reliably contribute to greater reproductive success across cultural contexts.

These findings support “state-dependent” theories of personality evolution, which propose that environmental conditions influence which personality traits confer reproductive advantages in different contexts.

The cross-sectional design limits definitive causal conclusions. Additionally, the brief personality measures used likely underestimates the strength of these relationships.

The study, “Consistency and Variation in Natural Selection on Personality Across 17 Countries,” was authored by Janko Međedović.