Personality Development in Adulthood: Studies of stability and change in a nationally representative sample of adult New Zealanders

Abstract

The development of personality in adulthood remains a topic of debate with direct implications for the conceptualisation of personality traits (McCrae & Costa, 1999; Roberts et al., 2008). However, with notable exceptions, comprehensive longitudinal investigations of the development of personality traits across a broad range of the adult life span are surprisingly rare. Through four systematic longitudinal investigations, the present thesis investigates the change and stability in the Big Six personality traits – Extraversion, Agreeableness, Conscientiousness, Neuroticism, Openness to Experience, and Honesty- Humility – in a nationally representative panel study of adult New Zealanders. Study 1 demonstrated the very high stability of the six traits, thus confirming the prediction of high temporal stability of personality traits. This study also provided the crucial test of the test-retest reliability of the personality scales used throughout this thesis. Study 2 demonstrated the systematic variability in the stability of personality traits across the adult life span. That is, personality traits tend to stabilise across younger adulthood, reach peak stability in middle age (i.e., late 40’s and early 50’s), and systematically destabilise thereafter. The findings of Study 3 indicated remarkable consistency in personality traits associated with a major natural disaster (namely, the 2010/2011 Earthquakes in Canterbury, New Zealand). The only meanlevel change from before to after the earthquakes was a small decrease in Emotional Stability (or an increase in Neuroticism) among those affected by the event. Finally, Study 4 investigated normative patterns of mean level change in personality traits and identified distinct developmental trajectories for the different traits with changes occurring across the entire adult life span. Collectively, these studies paint an interesting picture of both stability and change in personality traits, highlighting the need for an integrated perspective on personality development – one that incorporates both the intrinsic stability of the construct and early development, as well the continuing process of change.