Do traits remain stable throughout a person's life? Tins and other questions have prompted McCrae and Costa (2003) to look for evidence regarding the stability of personality traits. Interestingly, they found that basic personality traits change very little after the age of 30.
This finding requires some explanation.—First, traits of the Five-Factor Model do show some change during the decade of the 1920s. McCrae and Costa (2003) compared college students with adults and found that students scored higher than adults on neuroticism, extraversión, and openness to experience, whereas adults were higher in agreeableness and conscientiousness. Tins suggests that basic personality trait levels probably changes from late adolescence to adulthood. McCrae and Costa believe that during the period from about 18 to 30 years of age, people are hi the process of adopthig a stable configuration of traits, a configuration that remanís stable after age 30.
Second cross-sectional studies support the notion of stability of personality traits over the adult years. We might assume that cross-sectional studies—those that take a snapshot of two or more different age groups—might reveal quite different traits for young adults compared with older adults. However, this assumption lias little empirical support. For example, 75-year-old people have had many different experiences than 40-year-olds. In general, they have experienced stricter child-rearing practices, the Great Depression, World War II, the Vietnam War, retirement, and so on. By comparison, 40-year-old adults have grown up hi an age of lenient child-rearing practices, rapid technological advances, the threat of AIDS, widespread use of illegal drugs, and so on. However, despite these environmental and behavioral differences, the two groups are very similar in scores on the traits of the FFT (McCrae & Costa, 2003).
Third longitudinal studies—those that compare the same people over a period of thne—also reveal high levels of stability of personality traits. Early in then collaboration, Costa and McCrae (1978) conducted a longitudinal study expecting that personality traits would change over a period of time. To their surprise, they found a large degree of stability over a 10-year period. Later, Costa, Herbst, McCrae, and Siegler (2000) conducted a longitudinal study of nearly 2,300 middle-aged university of North Carolina alumni and found very small declines in neuroticism, extra-version, and openness to experience over a 6- to 9-year period. However, because the number of participants was quite large, these differences—though thiy—were statistically significant. Costa and associates (2000) used these results to esthnate that over a 40-year span, people at age 70 would score about one-half of a standard deviation lower than at age 30. These slight changes are about the same as those based on cross-sectional studies.
Fourth, the NEO-PI and the revised NEO-PI instruments are not the only methods of appraisal that support the notion of stability of traits. Personal niter-
Chapter 14 Eysenck, McCrae, and Costa's Trait and Factor Theories 427
views, self-reports, and judgments by significant others reveal high levels of personality stability (McCrae & Costa, 2003). In addition, a variety of personality inventories, including among others Cattells 16 PF scales (Cattell, 1949) and the Guilford-Zimmerman Temperament Survey (Guilford Zimmerman, & Guilford 1976), have revealed a basic stability of personality traits. For example, McCrae and Costa (2003) reported on an earlier study that had found very high correlations on the 10 scales of GZTS for adults over a 12-year period. These robust correlations prompted McCrae and Costa (2003) to conclude that "it becomes clear that most individuals obtain almost exactly the same scores on these tests on two different occasions separated by 12 years" (p. 109).
Fifth, after looking at massive amounts of evidence, McCrae and Costa (2003) were able to conclude that, "in the course of 30 years, most adults have undergone radical changes in their life structures. . . . And yet, most Mill not have changed appreciably in their standing on any of the five dimensions ofpersonality" (p. 112).
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