Predictions regarding the genetic architecture of traits under mutation-selection balance differ from those of selective neutrality above. If personality traits have been under mutation-selection balance, alleles underlying personality traits should be rarer than expected under selective neutrality (Eyre-Walker 2010). Second, the depletion of additive alleles should result in a substantial nonadditive component to the genetic variation underlying personality (Crnokrak and Roff 1995; Merila and Sheldon 1999; Stirling et al. 2002). Third, inbreeding should affect personality trait levels by pushing them in the opposite direction to that in which selection is acting; the exception is if the population mean is already at the optimum (i.e. stabilising selection), in which case inbreeding depression would not be expected because recessive allele effects pushing the trait away from its mean in each direction would cancel each other out on average.
