This is the 2007 version. Click here for the 2017 chapter 10 table of contents.

Persistence of Personality

William James wrote in 1887, "In most of us, by the age of 30, the character has set like plaster, and will never soften again." Like most easy generalizations in psychology, this poses a challenge to researchers. Some would like to show that James is wrong: personality can change during adulthood. But research into personality change in adulthood largely supports James's conclusion. McCrae and Costa (1994) summarized research findings from "a score of longitudinal studies over the past 20 years" using "a wide variety of samples, instruments, and designs":

What did William James write about personality change during adulthood? What have modern researchers found?

—Personality reaches final adult levels at about age 30. "Between 20 and 30, both men and women become somewhat less emotional and thrill-seeking and somewhat more cooperative and self-disciplined-changes we might interpret as evidence of increased maturity. After age 30, there are few and subtle changes...

—Individual differences in personality traits, which show at least some continuity from early childhood on, are also essentially fixed by age 30.

—Generalizations about stability apply to virtually everyone. Men and women, healthy and sick people, blacks and whites all show the same pattern. (p.173)

What did Block's longitudinal research show?

Jack Block, of the University of California at Berkeley, is known for the longest and most thorough study of personality change in adulthood. Block's sample was first studied when they were teenagers, again in their mid-30s, and again their mid-40s. Block used multiple, independent judges to assess personality. He took special care to prevent bias, concealing the identity of the subjects each time. Even so, the match between early and later personality assessments was striking.

Using this painstaking methodology, Block found a striking pattern of stability [on] virtually every one of the 90 rating scales employed... The most self-defeating adolescents were the most self-defeating adults; cheerful teenagers were cheerful 40-year-olds; those whose moods fluctuated when they were in junior high school were still experiencing mood swings in midlife. (Rubin, 1981)

University of Minnesota sociologist Jeylan Mortimer compared self-ratings in questionnaires of a group of University of Michigan freshmen, first tested in 1962, with the same group in 1976: 15 years later. The outcome: "Very high stability." (Rubin, 1981).

What was the most stable trait in the two studies involving older adults?

Two studies involving older adults produced similar results. A cross-section of ages-25 to 82 in the Boston study-was tested, then 10 years later tested again. The Baltimore study was similar, with different time intervals of testing: people of various ages were studied three times, six years apart each time. The results, in both cases, showed personality and attitudes remained stable. The most stable trait of all was introversion/extroversion or shyness. People who were talkative and cheerful at an early age were likely to remain that way.

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