Sigelman, C., K., de George, L., Cunial, K., & Rider, E. A. (2019). Life span human development (3rd ed.). Cengage Learning Australia Pty Ltd.
Having figured out that personality exhibits both continuity and change over the life span, developmentalists naturally want to know why people stay the same and why they change. What makes a personality stable? First, genetic makeup contributes to continuity (Krueger & Johnson, 2008). Second, lasting effects of childhood experiences may contribute; you have seen, for example, that parents can either help a child overcome a difficult temperament or contribute to it becoming an enduring pattern of response (Sanson et al., 2004; Sanson & Oberklaid, 2013). Third, traits may remain stable because people’s environments remain stable; playing consistent social roles like mother or engineer may be especially important in creating consistency in personality (Roberts, Wood, & Caspi, 2008). Fourth, gene-environment correlations may promote continuity. That is, genetic endowment may influence the kinds of experiences we have, and those experiences, in turn, may strengthen our genetically-based predispositions in a kind of snowball effect (Roberts & Caspi, 2003; also see Chapter 3). Thus, an extrovert’s early sociability will elicit friendly responses from others, cause them to seek out social activities and in the process strengthen their initial tendency to be extroverted – while the introvert seeks and experiences an environment that reinforces introversion.
What, then, might cause the significant changes in personality that some adults experience? Biological factors such as disease can contribute. The nervous system deteri-oration associated with Alzheimer’s disease (see Chapter 12), for example, can cause affected individuals to become moody, irritable and irresponsible (McCrae & Costa, 2003). Adults also change in response to changes in the environment, including major life events, changes in social and vocational roles and psychotherapy (Roberts et al., 2008; Lüdtke, Roberts, Trautwein, & Nagy, 2011; Sutin, Costa, Wethington, & Eaton, 2010).
Finally, change is likely prompted by the person-environment fit. Good fit between a person and their environment has been associated with personality consistency, while poor fit seems to encourage personality growth in directions that will better align the person and environment (Roberts & Robins, 2004). All things considered, the forces for continuity are likely to be stronger than the forces for change, perhaps in part because we want to retain our identities as individuals and keep building the same niches for ourselves even when we move, change jobs or make other life changes (Roberts et al., 2008).
Personality has a tremendous impact on life span development. Personal strengths such as emotional stability and conscientiousness are correlated with both good physical health and good mental health (Kern & Friedman, 2010; Lucas & Diener, 2008). Moreover, personality affects how we react to and cope with life events. For example, highly agree-able people are able to adjust better than most people to becoming disabled (Boyce & Wood, 2011), and people high in emotional stability (low in neuroticism) handle the death of loved ones better (Robinson & Marwit, 2006).
