Do people’s personality traits reflect when they were born? In a recent article in Psychological Science, Naemi D. Brandt (University of Hamburg) and a team of researchers from Germany and the United States examined how adult Big Five personality traits changed across generations of people in the United States. The traits—conscientiousness, agreeableness, neuroticism, extraversion, and openness to experience—make up a well-established framework that captures individual differences in how people act, feel, and think, which can influence life outcomes such as longevity, income, and happiness.
To investigate how personality traits develop with age and across generations, Brandt and colleagues used data from the Seattle Longitudinal Study, a large study that collected data from individuals of various ages in the Seattle area every seventh year between 1956 and 2012. Specifically, the researchers used personality data from 4,732 individuals born between 1883 and 1976 (19–91 years old) who completed at least two personality assessments.
Brandt and colleagues measured three types of variables: intraindividual change (how much an individual’s personality changed during the study), age-related differences (how age might impact changes in personality traits), and cohort-related differences (how different generations might show different traits and patterns of change).
Overall, the results fit with previous findings. Women on average were more agreeable and less extraverted than men. But some findings contradicted previous findings—for example, women had less neuroticism than men. The new analysis also found that individuals with more years of formal education tended to score higher on openness and that older individuals were, on average, more conscientious and agreeable and less extraverted and open than their younger counterparts.
Personality change across generations
Using different growth models, Brandt and colleagues found that people’s conscientiousness and agreeableness tended to increase as they aged, whereas neuroticism and openness tended to decrease. Extraversion remained more stable across the lifespan. Thus, as in previous research, individuals’ maturity-related traits and agency-related traits changed across time: That is, people became more conscientious, more agreeable, less neurotic, and less open. In this study, older age brought steeper declines in openness and shallower decreases in neuroticism.
“We found that later-born people were less agreeable and neurotic but more extraverted and open than their same-age, earlier-born peers. Later-born people also experienced steeper increases in agreeableness across time.”
Brandt et al. (2022)
Besides age-related differences, the researchers found cohort-related differences in all personality traits except conscientiousness. At age 58, members of later-born cohorts were less agreeable and neurotic and more extraverted and open than earlier-born cohorts. Later-born cohorts showed steeper increases in agreeableness across time, steeper age-related decreases in neuroticism, and age-related increases in agreeableness and openness. Interestingly, accounting for sex and education attenuated some of the cohort-related differences (especially in agreeableness and openness), suggesting that some of these differences might be related to historical changes in education and gender-related social roles.
The importance of history
Societal changes might play a role in some cohort-related differences. For instance, among later-born cohorts, women, but not men, reported higher levels of conscientiousness, which might reflect changes in women’s social roles across cohorts, such as greater participation in the workforce and increases in the relative importance of work-related goals. Similarly, increases in extraversion across cohorts might be related to the well-established finding that later-born cohorts perceive themselves as having more control over their lives and goals and thus have stronger beliefs in the possibility of change. Historical improvements in living conditions and accompanying changes in what people value and desire might also explain cohort-related differences in maturity-related traits, such as agreeableness.
But do generations really differ in their personality development? “The answer is mixed,” Brandt and colleagues explained. “People born at different times indeed differ, on average, in how conscientious, agreeable, neurotic, extraverted, and open they are. These differences were more pronounced in younger than older people for maturity-related traits, but the opposite was true for agency-related traits. We found little evidence that the rates by which personality changes differ across historical times.”
Overall, the results obtained hinted at delayed social-investment and maturity effects in later-born adults compared with those born earlier. The researchers also noted the need to further explore whether these findings generalize to other locations and countries, especially because “differential change trajectories between cohorts are assumed to be shaped by the socio-historical context in which development takes place.”
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Brandt, N. D., Drewelies, J., Willis, S. L., Schaie, K. W., Ram, N., Gerstorf, D., & Wagner, J. (2022). Acting like a baby boomer? Birth-cohort differences in adults’ personality trajectories during the last half a century. Psychological Science. Advance online publication. https://doi.org/10.1177/09567976211037971