The intrinsic maturation perspective emphasizes the role that genetic effects play in increasing the stability of personality. In a landmark exposition of this perspective, McCrae et al. (2000) concluded that the empirical evidence of “heritability, limited parental influence, structural invariance across cultures and species, and temporal stability all point to the notion that personality traits are more expressions of human biology than products of life experiences” (p. 177). Under this model, personality traits represent basic tendencies of behavior that are solely influenced by biological (i.e., genetic) mechanisms and “insulated from the direct effects of the environment” (McCrae & Costa, 2008, p. 164). The environment may alter the characteristic expressions of the basic tendencies (e.g., changing cultural norms for what constitutes politeness) or the biological bases of personality traits (e.g., brain damage), but environmental events such as occupational or romantic roles cannot have a direct impact on personality. Additional empirical support for this biologically-oriented perspective includes molecular genetic associations with personality (de Moor et al., 2010; Terracciano et al., 2010; Webb et al. 2012; Vinkhuyzen et al., 2012), parallel cross-cultural age-trends
