The studies showed little difference between men and women in the nature or extent of changes in personality.
By SANDRA G. BOODMAN
Are adults' personalities set by age 30, or do people change as they age?
For two decades this question has confounded researchers and has become the subject of contentious debate in the field of social psychology.
In 1980 an influential study concluded that significant personality change essentially ceases at 30. But a majority of more recent studies have found that personality evolves throughout a person's life.
Now a new report by a team of California researchers, using data from two large, long-term studies, has found that personality change occurs long after age 30 and in nearly all traits that standard tests measure.
The researchers also found that the traits of dominance and independence peak during middle age, more than a decade after it was originally believed such changes occurred.
"We found that personality changes with age, even though why this happens and how consistently it happens isn't clear," said Ravenna Helson, lead author of the study, which appears in the September issue of the Journal of Personality and Social Psychology.
Helson and her colleagues based their conclusions on 40 years of data from two studies of California residents, both of which were launched in the late 1950s.
The first study consists of about 500 male and female residents of Oakland and Berkeley born in the 1920s who were interviewed periodically as children and then at ages 33, 49, 62 and 75.
The second study involves 140 women who were selected in 1957 when they were seniors at Mills College in Oakland. These women were surveyed at ages 27, 43, 52 and 61.
Both groups, which consisted largely of white, middle-class, highly educated people, periodically completed a widely used personality test called the California Psychological Inventory. The test measures 20 traits, including tolerance, self-acceptance, self-control and flexibility.
Helson and her team found that there were few differences between men and women in the nature or extent of personality change, a finding consistent with other studies.
Women in the Mills study who worked between ages 27 and 43 increased more in dominance than men or women in the Oakland group and more than those in the Mills study who did not work. Those who got divorced, especially if they were not working, showed decreases in that trait.
Overall, researchers found that self-control and impulse control increased with age, but social vitality and the perception of one's sexual attractiveness decreased.