1. Developmental change and stability of personality

2. Is personality more stable across the lifespan than the many physical changes might suggest?

3. Every personality develops continually from the stage of infancy until death, and throughout this span it persists even though it changes.
―Gordon W. Allport

4. Two fundamental questions about personality change
Do people typically show similar patterns of development in personality trait levels (similar paths)? (Assessed by differences in the mean level of certain traits at different life stages)
Do people display rank-order consistency in their personality trait levels over time? (Analogous to the issue of test-retest reliability, but assessed at very long intervals)

5. Developmental changes in mean levels of personality traits
Meta-analysis of longitudinal studies (Roberts et al., 2006):
The average levels of conscientiousness, emotional stability, and the assertive aspects of extraversion tended to increase during young adulthood and early middle age.
A similar but weaker pattern was evident for agreeableness.
The average levels of the sociable and lively aspects of extraversion showed a slight decrease during young adulthood and a further slight decrease toward the end of middle age.
The average level of openness to experience showed moderate increases between adolescence and young adulthood, remaining stable through middle age, but then showing a modest decline during late middle age.

6. Why do these developmental changes occur?
Changes in the levels of certain hormones or neurotransmitters?
Changes resulting from important life experiences and changing social roles?
Exposure to different people and ideas at different stages of life?
Decreases in physical vitality and health?

7. (Rank-order) stability of traits across years and across the life span
Costa and McCrae (1988b) studied nearly 1000 adults whose ages at the start of the study ranged from 25 to 84.
Over a six-year test-retest interval, the traits they studied were highly stable, with test-retest correlations averaging about .70
A second study by Costa and McCrae (1992c), with a seven-year test-retest interval, revealed similar results.
A third study by Ashton and Lee (2005b), with a nine-year test-retest interval and using different inventories to measure the same traits, revealed similar, but slightly more variable, results.
Interestingly, these results did not vary much according to the specific trait being considered, or whether the respondents were in their 30s, their 40s, their 50s, or their 60s during the time of the study.

8. Stability of personality trait levels across a nine-year period
NEO-PI-R scale (1994)
HEXACO-PI scale (2003)
Correlation
Order
Organization
.71
Angry hostility
Patience
-.64
Anxiety
.63
Assertiveness
Social boldness
.69
Openness to aesthetics
Aesthetic appreciation
Modesty
.55
Source: Ashton and Lee (2005b)

9. Stability across longer periods of time during adulthood
Costa and McCrae (1992c) administered personality measures to participants at several points over the course of 24 years.
The average stability of the measured personality traits across this time period was impressively high (.65). Across a shorter interval of 12 years, it was .70.

10. Stability during adolescence and young adulthood
McCrae et al. (2002) found average stability coefficients of .40 to .50 in 230 American adolescents over a 4-year period.
Robins et al. (2001) found average stability coefficients of about .60 in 270 American college students over their four college years.
On the other hand, Finn (1986) found that traits measured in college were correlated only .35, on average, with the same traits measured 30 years later.
Nevertheless, Finn’s data revealed average stability coefficients of about .55 over a 30-year interval that began when the trait levels were first measured during the college years.
Taken together, these findings suggest that personality is undergoing change during the late-adolescent and college-age years.

11. Personality structure during childhood (i. e
Personality structure during childhood (i.e., what are the fundamental trait dimensions in childhood?)
The evidence so far suggests that, at least during much of childhood, personality structure is similar to that observed during adulthood.
For example, factor analyses of teachers’ ratings of children’s personalities have produced the Big Five factors (Digman & Takemoto-Chock, 1981; Shiner & Caspi), although the Openness to Experience dimension does not always emerge as strongly as the others.
As one would expect, the structure of personality in infants or very young children is somewhat less clear.

12. Developmental change in personality traits during childhood
Lamb et al. (2002) found that, across personality assessments at ages 2, 3, 6, 8, and 15, the typical child became somewhat lower in extraversion, higher in agreeableness, and higher in conscientiousness.
They also became somewhat lower in emotional stability between the ages of 3 and 6, and most became somewhat lower in openness to experience between the ages of 8 and 15.
The interpretation of these findings is complicated by the fact that the personality trait scales had low reliabilities during the early periods, especially extraversion and openness to experience.

13. Test-retest stability of traits during childhood
In the same study just described, Lamb et al. (2002) found that children’s personalities were relatively stable during adjacent testing intervals (i.e., between ages 2 and 3, 3 and 6, 6 and 8, and 8 and 15), with correlations above .50 for each of the Big Five factors.
However, between the beginning (age 2) and ending ages (age 15) examined in the study, the children’s personalities were much less stable, with correlations of about .20 for each of the Big Five factors.

14. The development of self-esteem across the lifespan
Robins and Trzesniewski (2005) found that average self-esteem scores were
fairly high during childhood
tended to drop sharply during adolescence, but to “mixed” rather than low levels
remain at this moderate level during young adulthood
rise during middle age to reach rather high levels by age 65
drop again during old age
fairly stable over time, particularly when the time interval between testings was short, rather than long