Recent longitudinal and cross-sectional aging research has shown that personality traits continue to change in adulthood. In this article, we review the evidence for mean-level change in personality traits, as well as for individual differences in change across the life span. In terms of mean-level change, people show increased selfconfidence, warmth, self-control, and emotional stability with age. These changes predominate in young adulthood (age 20-40). Moreover, meanlevel change in personality traits occurs in middle and old age, showing that personality traits can change at any age. In terms of individual differences in personality change, people demonstrate unique patterns of development at all stages of the life course, and these patterns appear to be the result of specific life experiences that pertain to a person's stage of life.Keywords personality development; personality traits; mean-level change; individual differences in change Personality traits are defined as the relatively enduring patterns of thoughts, feelings, and behaviors that distinguish individuals from one another. Whether personality traits continue to develop in adulthood depends in part on how one defines "relatively enduring." In the past, some researchers took that phrase to mean-and the empirical literature to indicatethat personality traits stopped changing in adulthood (McCrae & Costa, 1994). Since 1994, cross-sectional and longitudinal studies of personality-trait change in adulthood have forced a reevaluation of the assumption that personality traits do not change in adulthood (e.g., Mroczek & Spiro, 2003;Roberts, Walton, & Viechtbauer, 2006;Srivastava, John, Gosling, & Potter, 2003). Research now shows that personality traits continue to change in adulthood and often into old age, and that these changes may be quite substantial and consequential. In this article, we provide an overview of the evidence for personality-trait change in adulthood and outline some of the possible reasons for these changes. Before we discuss these findings further, we describe what we mean by change.
DEFINITIONS OF PERSONALITY CONTINUITY AND CHANGEResearchers often fail to clarify what they mean when they describe personality as consistent or changeable. Part of the difficulty arises from the multiple indices for tracking continuity and change-such as mean-level change, rank-order consistency (relative ordering of people over time), structural consistency (e.g., similar factor structures over time), and individual differences in change. A complete understanding of personality continuity and change can only come from a thorough examination of multiple indices, as they are often independent of