Based on early work examining the stability of personality across the lifespan, McCrae and Costa (1994) provocatively claimed that personality traits were relatively fixed after age 30, as the best available evidence at the time indicated that test-retest stability peaked at this point. Of course, personality traits do exhibit change (test-retest stability is never perfect), but in the context of the larger lifespan trend, age 30 appeared to be a turning point from rather large gains in stability during adolescence into “firm” adult personality constructs. Terracciano, Costa, and McCrae (2006) found evidence supportive of this claim, in that personality stability was uncorrelated with age after age 30 for each Big Five factor and facet. One explanation for the age 30 plateau (described more fully in the next section) is that “mature” personality traits (i.e., increased dominance, agreeableness, conscientiousness, and emotional stability) are required for adult occupational roles. Therefore, individuals who already possess this constellation of traits might display greater stability at a younger age. In contrast, Terracciano, McCrae, and Costa (2010) found evidence that the plateau of stability at age
