Behavior Genetics Research on Personality: Moving Beyond Traits to Examine Characteristic Adaptations

This paper argues that behavior genetics research on personality should expand beyond universal traits to include characteristic adaptations. Trait research examines broad, decontextualized, and universal domains such as the Five Factor Model. Characteristic adaptations are more contextualized than traits, such as goals and life strategies as responses to specific life demands. The paper is organized into three sections: (1) a review of the abundance of behavior genetics research on personality traits, which has reached a convergent point at which few further findings are reported beyond the classic distribution of high genetic and non- shared environmental influences with little to no shared environmental effect; (2) a review of existing behavior genetics research on characteristic adaptations that, although limited in volume, has demonstrated patterns far less consistent than traits; and (3) a discussion on future directions and important limitations to consider in conducting and interpreting behavior genetics research on non-trait personality. The connection between characteristic adaptations and contextualized life outcomes, the preponderance of homogenous findings on traits, and the sparse yet promising findings of characteristic adaptations, all support the need for behavior genetics research on personality to expand beyond the broad trait level to characteristic adaptations and beyond.

Shared environmental effects bias phenotypic estimates of assortative mating in a wild bird

Assortative mating is pervasive in wild populations and commonly described as a positive correlation between the phenotypes of males and females across mated pairs. This correlation is often assumed to reflect non-random mate choice based on phenotypic similarity. However, phenotypic resemblance between mates can also arise when their traits respond plastically to a shared environmental effect creating a (within-pair) residual correlation in traits. Using long-term data collected in pairs of wild blue tits and a covariance partitioning approach, we empirically demonstrate that such residual covariance indeed exists and can generate phenotypic correlations (or mask assortative mating) in behavioural and morphometric traits. These findings (i) imply that residual covariance is likely to be common and bias phenotypic estimates of assortative mating, which can have consequences for evolutionary predictions, (ii) call for the use of rigorous statistical approaches in the study of assortative mating, and (iii) show the applicability of one of these approaches in a common study system.