In Brief

While many may suspect that people's personalities are fixed in childhood, new research suggests that most people's personalities evolve throughout their lives.

Personality changes in men and women older than 30 were demonstrated in a study conducted at the University of California, Berkeley, and published recently in the Journal of Personality and Social Psychology (Vol. 84, No. 5).

The researchers, who evaluated data from 132,515 adults, ages 21-60, looked at overall life span trends in the "Big Five" personality traits--conscientiousness, agreeableness, neuroticism, openness and extraversion.

"One of the major theories of personality asserts that personality traits are largely set by genetics, and, by consequence, changes in personality traits should slow as other functions of maturation slow," says lead researcher and psychologist Sanjay Srivastava, PhD. "We set out to test that."

What he and his team found contradicted long-held assumptions about when personalities are set. Conscientious-ness, a trait marked by organization and discipline, and linked to success at work and in relationships, was found to increase through the age ranges studied, with the most change occurring in a person's 20s. Agreeableness, a trait associated with being warm, generous and helpful, bucked the theory that personalities don't change after 30. On the contrary, people in the study showed the most change in agreeableness during their 30s and continued to improve through their 60s. This even happened among men, which debunks the concept of "grumpy old men," Srivastava says.

"The levels of change in these two traits seem to model what would make sense with adult roles," Srivastava says. "Conscientiousness grows as people mature and become better at managing their jobs and relationships, and agreeableness changes most in your 30s when you're raising a family and need to be nurturing."

Most of the observed personality changes were generally consistent across gender lines, except for neuroticism and extraversion, with young women scoring higher than young men. However, the gap between men and women diminished over time.

"When people talk about the 'Big Five,' neuroticism is probably the biggest sex difference--it's something that's been demonstrated before," Srivastava says. The difference in neuroticism is only apparent in youth and young adulthood and narrows as people age, Srivastava says.

Openness showed small declines in both men and women over time, a change that indicates less interest in forming new relationships, and may infer greater interest in spending time with a small group of well-known relatives and friends as people age, Srivastava says.

The large data set--collected over the Internet--allowed for the traits to be studied across many age groups, Srivastava says. Future research on the same data set will look into personality differences across regions, climates and population densities.

Psychologists Oliver P. John, PhD, and Samuel D. Gosling, PhD, and computer scientist Jeff Potter contributed to the research.