Our results suggest a polygenic model in which a large number of variants individually explain a small proportion of the variance. Moreover, we observed a linear relationship between the length of a chromosome and the proportion of the variance explained by that chromosome for extraversion, which also supports a model in which many variants affect the variance of the trait. As none of the chromosomes significantly differed from the regression line, no major gene effects are supported in our analyses. The linear relationship between chromosome length and variance explained was substantially smaller for neuroticism, which was expected given the smaller genetic variance that can be attributed to common SNPs.
