To support the idea that everyone's personality is stable would mean that it does not change. Yet you probably remember how you evolved as a result of life experiences, such as the education and attention you received in early childhood, the successes and failures you experienced later in life, and other transformative events.
But does the personality change throughout life? And are these observed changes due to an intrinsic maturation of the individual, or to the influence of lived situations?
To answer these questions, one of the most difficult tasks in the study of personality has been to develop a taxonomy of traits. Researchers have long wondered what are the most reliable models of trait covariation across individuals.
Establishing a taxonomy for youth has been particularly challenging, as children mature to display an increasingly differentiated set of traits. Children evolve rapidly from displaying a small number of emotions-interest, satisfaction, and distress-during infancy to displaying an expanded set of emotions-including joy, sadness, anger, fear, empathy, pride, shame, and guilt-by age 3 (Eisenberg, 2000; Lewis, 2000).
In adulthood, other changes can be observed: we tend to become more socially dominant, more conscientious (organized and reliable), and more emotionally stable between the ages of 20 and 40, while openness to new experiences tends to decrease with age (Roberts, Walton, & Viechtbauer, 2006). In other words, even though we consider our personality to be relatively stable, changes do occur.
Furthermore, the development of our personality during childhood has lasting consequences for us. For example, studies show that some of our career success and job satisfaction later in life can be explained by what our personality was like as children .
Findings from a longitudinal study in Germany
A study of a heterogeneous sample of 14,718 Germans throughout adulthood led to several conclusions.
First, age has a complex curvilinear influence on average personality levels. Our personality changes rapidly during our youth, stabilizes in adulthood, and changes again in later life.
Second, the stability of the rank order of emotional stability, extraversion, openness and agreeableness, in our personality profile, follows an inverted U-shaped function, peaking between the ages of 40 and 60 and decreasing thereafter, while conscientiousness shows a steadily increasing stability of order in adulthood. In short, the older we get, the more our degree of consciousness increases.
Third, personality predicts the occurrence of several major life events (selection effects) and changes in response to the experience of these events (socialization effects), suggesting that personality can vary due to factors other than intrinsic maturation, and thus is influenced by environmental factors.
In summary, research shows that personality changes throughout the life course, but that it undergoes more pronounced changes at younger and older ages, and that this change is partly due to social demands and life experiences.
 Judge, T. A., & Higgins, C. A. (1999). The big five personality traits, general mental ability, and career success across the life span. Personnel Psychology, 52, 621-652; Staw, B. M., Bell, N. E., & Clausen, J. A. (1986). The dispositional approach to job attitudes: A lifetime longitudinal test. Administrative Science Quarterly, 31, 56-77.