How have these broad, historical theories of personality development been applied to the empirical trend of increasing trait stability? Although there are a great number of modern theories of personality development (see Mroczek & Little, 2006), the two frameworks that have been most interested in explaining increasing stability are the Five Factor Theory (FFT; McCrae & Costa, 2008) and social personality models (SPMs). These SPMs have been alternatively called the neo-socioanalytic (Roberts & Woods, 2006) or the sociogenomic (Roberts & Jackson, 2008) model of personality, and they are highly connected to social investment theory (Roberts, Wood, & Smith, 2005). Therefore, we refer to this general class of theories that emphasize social inputs into personality development as SPMs. The FFT takes the strong position that personality development is guided by intrinsic processes. SPMs emphasize that genes or intrinsic processes set the stage for personality development. They hold that lifespan trends, however, are primarily a function of exogenous forces, most notably the social environment. Importantly, even in the primary proponents’ most polemic work, both sides have acknowledged that genes are a substantial
