While they make different sets of predictions, these three main mechanisms for maintaining genetic variation are not mutually exclusive possibilities. For example, if genetic variation in personality traits is under very weak selection (e.g. because trade-offs reduce its fitness consequences), many mutations with small effects will be governed largely by drift and the overall genetic architecture will look like that of selective neutrality with only a slight bias in the frequency distribution of alleles (Eyre-Walker 2010). It is also important to note that current genetic architecture reveals past evolutionary processes, so implications regarding selective pressures on personality traits may not be reflected in today's environment. With these issues in mind, predictions from the different evolutionary mechanisms are summarised in Table 1. (Hill et al. 2008),
