Big Five personality traits and Reproductive Success: a meta-analysis

This meta-analysis aims to synthesize correlations between ‘Big Five’ personality traits and reproductive success (i.e., number of children) in humans. The number of children is considered a good indicator of long-term reproductive success, a central component of biological fitness (Penke & Jokela, 2016). Understanding how personality traits are associated with fitness outcomes is essential for identifying the specific evolutionary mechanisms that maintain individual differences in the population (Međedović et al., 2018). A previous meta-analysis in wild and domesticated animals concluded that variation in personality is primarily maintained through trade-offs in fitness consequences across contexts (Smith & Blumstein, 2008). Similarly, Penke, Denissen & Miller (2007) argued that maintenance of personality traits in humans may be accounted for by balancing selection through environmental heterogeneity and frequency-dependent selection, rather than selective neutrality or mutation-selection processes. The authors argue that personality traits can be viewed as individual reaction norms, producing environment-contingent patterns of behaviors and fitness (Penke et al., 2007). As a result, this makes balancing selection a plausible mechanism because fitness advantages of traits may vary across environmental and social contexts (but see Zietsch, 2024). Consequently, if balancing selection is the primary evolutionary mechanism maintaining personality differences, we would expect that, across a wide range of studies, associations between personality traits and number of children will be small or non-existent. However, phenotypic plasticity allows individual to seek out and adapt to their environmental niche, meaning that study-level variables such as country, socio-economic status, or cultural context could strongly moderate associations between personality traits and reproductive success (Penke & Jokela, 2016). Observing such patterns would support balancing selection, whereas mutation-selection would predict consistent directional associations and selective neutrality would predict no systematic differences or moderation at all. Therefore, in addition to being the first meta-analysis to synthesize associations between ‘Big Five’ personality traits and reproductive success, this study provides an indirect empirical test of balancing selection as primary evolutionary mechanism for the maintenance of personality traits in humans.