estimated genetic relationship of >0.025 (~ closer than third or fourth cousins). This led to an exclusion of 7,957 individuals, resulting in a retained dataset of 4,902 individuals. Population structure (i.e. differences in allele frequencies between subpopulations which might also differ in personality) can inflate the genetic variance estimates, so to control for this we included the first 20 principal components (eigenvectors of the genetic relatedness matrix) and cohort status (i.e. which subsample they belong to) as covariates in the analysis. We checked to what extent population structure would have affected the results by comparing results from analyses with and without the 20 principal components as covariates.
