Can we predict who is likely to change in personality and who is likely to remain the same? In a fascinating longitudinal study, Caspi and Herbener (1990) studied middle-aged couples over an 1 1-year period. The couples were tested twice, once in 1970 and again in 1981. All the subjects had been born in either 1920-21 or 1928-29 and were part of a lar ger longitudinal project.
The question that intrigued Caspi and Herbener was this: Is the choice of a marriage partner a cause of personality stability or change? Specificall , if you marry someone who is similar to you, do you tend to remain more stable over time than if you marry someone who is different from you? They reasoned that similarity between spouses would support personality stability , since the couple would tend to reinforce one another on their attitudes, to seek similar external sources of stimulation, and perhaps even to participate together in the same social networks. Marrying someone
Females (25 per group)
Low similarity Moderate similarity High similarity
Males (25 per group)
Females (25 per group)
Males (25 per group)
The figure shows the stability of personality over time as a function of the similarity (lo , medium, or high) of the person to his or her spouse. Men and women who are married to someone similar to themselves in personality show the highest levels of personality stability over time.
who is unlike oneself, in contrast, may of fer attitudinal clashes, exposure to social and environmental events that one might not otherwise seek alone, and generally create an environment uncomfortable to maintaining the status quo.
Using personality measures obtained on both husbands and wives, Caspi and Herbener divided the couples into three groups: those who were highly similar in personality, those who were moderately similar in personality , and those who were low in similarity. Then they examined the degree to which the individuals showed stability in personality over the 1 1-year period of midlife in which they were tested. The results are shown in Figure 5.6.
As you can see in Figure 5.6, the people married to spouses who were highly similar to themselves showed the most personality stability . Those married to spouses least similar to themselves showed the most personality change. The moderate group fell in between. This study is important in pointing to a potential source of personality stability and change—the selection of spouses. It will be interesting to see whether future research can document other sources of personality stability and change— perhaps by examining the selection of similar or dissimilar friends, or by selecting college or work environments that show a good "fit" with one s personality traits upon entry into these environments (Roberts & Robins, 2004).
SUMMARY AND EVALUATION_
Personality development includes both the continuities and changes in personality over time. There are three forms of personality stability: (1) rank order stability is the maintenance of one's relative position within a group over time, (2) mean level stability is the maintenance of the average level of a trait or characteristic over time, and (3) personality coherence is predictable changes in the manifestations of a trait. We can examine personality development at three levels of personality analysis—the population level, the group dif ferences level, and the individual dif ferences level.
There is strong evidence for personality rank order stability over time. Temperaments such as activity level and fearfulness show moderate to high levels of stability during infancy . Activity level and aggression show moderate to high levels of stability during childhood. Bullies in childhood tend to become juvenile delinquents in adolescence and criminals in adulthood. Personality traits, such as those captured by the five-factor model, show moderate to high levels of stability during adulthood As a general rule, the stability coef ficients decrease as the length of time between th two periods of testing increases.
Personality also changes in predictable ways over time. With respect to the Big Five, a consensus is now emer ging that Neuroticism generally decreases over time; people become a bit more emotionally stable as they age. Furthermore, Agreeable-ness and Conscientiousness tend to increase over time. All these changes suggest increased maturity, as the sometimes tumultuous times of adolescence settle out into the maturity of adulthood. From early adolescence to early adulthood, men' s self-esteem tends to increase, whereas women' s self-esteem tends to decrease. In adulthood, there is some evidence from a study of creative architects that flexibility an impulsivity decline with increasing age. Sensation seeking also declines predictably with age. And, in women, femininity tends to decrease over time, notably from the early forties to the early fifties. On the other hand, several studies suggest that th personality characteristics of autonomy , independence, and competence tend to increase as people get older , especially among women.
In addition to personality change due to age, there is also evidence that mean personality levels can be af fected by the social cohort in which one grows up. Jean Twenge has documented several such ef fects, most notably on women' s levels of assertiveness or dominance. Women's assertiveness levels were high following the 1930s in which women had to be extremely independent; they fell during the 1950s and 1960s when women were lar gely homemakers and fewer became professionals. From 1967 to 1993, however , women's levels of assertiveness increased, corresponding to changes in their social roles and increasing participation in professional occupations.
Personality also shows evidence of coherence over time. Early measures of personality can be used to predict socially relevant outcomes later in life. High levels of neuroticism in both sexes and impulsivity in men, for example, predict marital dissatisfaction and divorce. Neuroticism early in adulthood is also a good predictor of later alcoholism and the development of emotional problems. Impulsivity plays a key role in the development of alcoholism and the failure to achieve one's academic potential. Highly impulsive individuals tend to get poorer grades and drop out of school more than their less impulsive peers. Children with explosive temper tantrums tend to manifest their personalities as adults through downward occupational mobility , more frequent job switching, lower attainment of rank in the military , and higher frequencies of divorce. People who are impulsive at age 18 tend to do more poorly in the workplace—they attain less occupational success and less financial securit . Work experiences, in turn, appear to af fect personality change. Those who attain occupational success tend to become happier, more self-confident, and less anxious over time
Although little is known about what factors maintain these forms of personality stability and coherence over time, one possibility pertains to our choices of marriage partners. There is evidence that we tend to choose those who are similar to us in personality, and, the more similar our partners, the more stable our personality traits remain over time.
How can we best reconcile the findings of considerable personality stability ove time with evidence of important changes? First, longitudinal studies have shown conclusively that personality traits, such as those subsumed by the Big Five, show substantial rank order stability over time. These personality traits also show evidence of coherence over time. Bullies in middle school, for example, tend to become criminals in adulthood. Those with self-control and conscientiousness in adolescence tend to perform well academically and well in the workplace later in life. In the context of these broad-brush strokes of stability , it is also clear that people show mean level changes with age—as a group people become less neurotic, less anxious, less impulsive, lower in sensation seeking, more agreeable, and more conscientious. Some changes are more pronounced in women—they become less feminine and more competent and autonomous over time. And some personality change af fects only some individuals, such as those who succeed in the workplace. In short, although personality dispositions tend to be stable over time, they are not "set in plaster" in the sense that some change in some individuals some of the time.
Personality Development 138 Rank Order Stability 138 Mean Level Stability 139 Mean Level Change 139
Personality Coherence 139 Temperament 143 Longitudinal Studies 145 Actometer 145
Stability Coefficient 145 Validity Coefficient 145 Self-Esteem 153 Cohort Effects 159
PART T W O
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