This raises the question of ‘missing heritability’: if personality is heritable with 30–60% of the variance explained by genetic effects, why can we not find any specific genetic variants to account for that heritability? Missing heritability has been observed to a large extent in almost all complex traits (Maher, 2008). Proposed explanations focus on: many variants of very small effect that are yet to be found; rare variants that are poorly detected by available genotyping arrays that focus on variants present in at least 5% of the population; structural variants poorly captured by existing arrays, such as copy number variations; and low power to detect epistasis (interaction between genes) (Manolio, et al., 2009). Newer technologies (e.g. whole genome sequencing) and novel statistical approaches combined with larger samples and meta-analyses will contribute to our understanding of the genetic architecture of complex traits.
