D-Day, June 6,1944. President Kennedy’s assassination. The first moon landing. The fall of the Berlin Wall.

Landmark events like these become etched into our collective consciousness, particularly if we witnessed them during our adolescence or young adulthood.

But to what extent do these world-changing events shape our individual character? According to many theories, the fashion, music, cultural values, and global events of our formative years leave on us some psychological marks — traits we share with our peers.

We tend to view our preferences and idiosyncrasies as inherently singular — a unique cocktail of traits that emerges from mixing genetic predispositions with our familial and social experiences. But ever since Karl Mannheim proposed his theory of generations in a seminal 1923 essay, researchers have tried to elucidate the influence of the sociocultural environment — including those influences unique to each generation — on aspects of our personalities and attitudes.

This work is not without its skeptics. Many social scientists regard the evidence of birth cohort effects on the individual to be inconclusive at best. But others believe they have uncovered some clear, collective traits that distinguish one age group from another.

Across the Ages

Social scientists generally define birth cohorts by the hugely impactful cultural events or changes that serve as bookends of an era. This leads to widely accepted traits ascribed to each generation. Baby Boomers (born between 1946 and 1964) are viewed in relation to the postwar climate of prosperity and the resulting rise of consumerism; Millennials (born between 1980 and 2000) are seen as the last generation to grow up without the full ubiquity of the Internet and the first to come of age under the somber specter of 9/11. In between are those in Generation X, or Gen X-ers, people born between 1965 and 1979 who witnessed the birth of MTV and became poster children for disaffected cynicism.

But isolating the real effects of birth cohort on individuals can be challenging. Typical methods like cross-sectional analyses or longitudinal studies are designed to capture data at a single moment in time or in a single group across time; to get at the influence of generation, researchers must be able to compare different people who were the same age at different times. One approach designed to achieve this is cross-temporal meta-analysis, a method devised by San Diego State University psychology professor and APS Fellow Jean Twenge. Cross-temporal meta-analysis involves comparing data from widely used psychological questionnaires taken by people of a particular age at different points in time (e.g., a survey given to college freshmen in 1980, 2000, and 2013).

This innovative method carries some limitations, though: It compiles and compares mean scores rather than results from individual participants. And although many different samples are often incorporated into the analysis, some of those individual samples may be small or prone to selection bias, according to critics such as Clark University psychology professor Jeffrey Jensen Arnett and Kali Trzesniewski of the University of California, Davis.

All About “Me”

Twenge has used cross-temporal meta-analysis to examine the degree to which Millennials live up to the moniker “Generation Me,” even writing a book by that name in which she analyzes several dimensions of personality such as self-esteem, locus of control, and narcissism. She has found that self-esteem, after declining during the 1960s to the late 1970s, has steadily risen since 1980. But Twenge’s most controversial findings have centered on the topic of narcissism. Her 2008 study examining college students’ scores on the Narcissism Personality Inventory (NPI) from 1979 to 2006 concluded that in 2006, 30% more students scored above the original (1979) NPI average than had scored above the same average in the original study. These results conform to the popular conception of Millennials as possessing uniquely inflated egos born out of the self-esteem movement begun in the late 1970s that prioritized blanket praise over actual performance.

Some researchers object to Twenge’s sampling methods and, consequently, her results. A study led by Trzesniewski examined NPI data from two California university campuses; some subscales of the NPI showed decreases and others showed increases, but the authors found no increase in overall scores. They also did not find any change in self-enhancement — essentially, the belief that you are smarter than you actually are — which is often considered a corollary of narcissism.

Researchers have hypothesized that birth cohort may also influence the ways individuals perceive their control over their lives. The Internal–External Locus of Control Scale was devised in 1966 to measure the degree to which people believe that they are able to control their own circumstances. In our increasingly individualistic culture, it seems logical that members of “Generation Me” would endorse the idea they are in control of their own destiny more than their Baby Boomer and Gen-X counterparts.

However, Twenge found that college students in 2002 had a more external locus of control than they did in 1960 — meaning they held a stronger belief that the events in their lives were the result of outside forces beyond their control. But when Trzesniewski and M. Brent Donnellan of Texas A&M University examined samples drawn from the Monitoring the Future project, a large-scale study that has surveyed high school seniors since 1976, they found no correlation between generation and locus of control. There did appear to be evidence, though, that Millennials are more cynical about the utility of school and the trustworthiness of government than previous generations. Both an increasingly external locus of control and increased cynicism could be symptomatic of the increased social alienation that has accompanied expanding personal independence: As our society has become more self-focused and less communal, we’ve become more wary of the social institutions on which past generations relied heavily.

The Erosion of Empathy

Changes in the sociocultural environment have implications not only for how we view ourselves, but also for how we view one another. A group of University of Michigan researchers, led by psychological scientist Sara H. Konrath, has used the cross-temporal meta-analysis method to examine changes in different dimensions of empathy over generations. They have found significant decreases since the late 1970s in both the emotional component of empathy, Empathic Concern, which indicates the level of a person’s sympathy for others’ misfortunes, and the more cognitive component of Perspective Taking — the tendency to see a situation from another person’s point of view. Since both of these measures are correlated with all kinds of prosocial behaviors, from helping strangers carry their heavy items to increased charity donations and volunteer hours, the decline in empathy could have real-world consequences. Many also see this effect as the counterpart of an increasing egocentrism among Millennials compared with previous generations.

This “more me, less you” view finds support in research on cohort differences in attachment styles. In a meta-analysis of more than 90 samples, younger generations showed increases in insecure attachment styles (e.g., dismissing, preoccupied, and fearful) and decreases in secure attachment styles, according to the same research group. One of the most striking findings from this study was the increased proportion of subjects who agreed with the statement “I am comfortable without close emotional relationships.” The authors posit that this change may be related to various socio-environmental factors, such as changing parenting practices and the rise of social media. However, since a number of societal changes co-occur, it is difficult to disentangle cause and effect in such studies.

Possible echoes of these alienating effects can be seen in patterns of psychopathology across cohorts. Not only have depression and anxiety levels increased from generation to generation, so have various other metrics on the Minnesota Multiphasic Personality Inventory (MMPI), the most widely used personality assessment tool. These increases occurred in the scales for paranoia, schizophrenia, hypomania, and hysteria, among others.

Intriguingly, similar generational increases in anxiety and depression symptomology have been reported in populations in New Zealand and China, suggesting that there may be some aspects of cohort influence that cross boundaries of country and culture. Indeed, with the advent of the Internet, the sociocultural environment of Millennials has inflated to a size not experienced by any previous generation — one that is truly global. But does the new expanse of today’s sociocultural landscape have implications for how people engage with their communities closer to home?

It’s the Economy, Too

While generations are typically delineated through social determinants like political events and social movements, the economy is a powerful moderator of generational effects on individuals, some recent studies show. Economic declines have been linked to health problems brought on by stress and hunger, even higher mortality rates, but they can have powerful — and lasting — psychological impacts on an entire generation, as well.

Although well-being generally increases over the lifetime of individuals from all generations, research published in 2013 showed that the extent of that increase varies from cohort to cohort.

Psychological scientist Angelina R. Sutin of the Florida State University College of Medicine conducted the study while at the National Institute on Aging (NIA). She and her colleagues at NIA predicted that people born around the same time may have had unique experiences that shape the way they evaluate happiness and optimism. They hypothesized that the level of well-being a person reports would, therefore, vary according to his or her birth year.

And that’s indeed what they found. Using two large-scale longitudinal studies, the National Institutes of Health’s Baltimore Longitudinal Study of Aging and the Centers for Disease Control’s National Health and Nutrition Examination Survey, Sutin and colleagues examined data from several thousand people over 30 years, including more than 10,000 reports on well-being, health, and other factors.

When the researchers analyzed the data across the whole pool of participants, older adults had lower levels of well-being than younger and middle-aged adults. But when they analyzed the same data while taking birth cohort into account, a different trend appeared: Life satisfaction increased over all participants’ lifetimes. This trend remained even after factors like health, medication, sex, ethnicity, and education were taken into account.

So what explains the different results?

While life satisfaction increased with age for each cohort, older birth cohorts — especially people born between 1885 and 1925 — started off with lower levels of well-being in comparison with people born more recently. (They lived through the Great Depression, after all.) Looking at life satisfaction across all of the participants, regardless of when they were born, obscured the fact that each cohort actually showed the same underlying trend of life satisfaction increasing with age.

The opposite was true as well: Generations that experienced the postwar economic boom of the mid-20th century had consistently higher levels of well-being throughout life compared with other cohorts. Although we all tend to get happier as we age, economic conditions during young adulthood seem to play a vital role in calibrating our well-being baselines.

Poor economies also affect our attitudes toward civic matters. Economists Paola Giuliano and Antonio Spilimbergo found that people who spent their formative years (defined as ages 18–25) in a recession tend to believe in luck as a larger driver of success than hard work, favor increased government redistribution practices, and show decreased trust in government institutions like Congress. (Interestingly, despite these patterns, overall political attitudes were not shown to be affected by economic slowdowns.) It seems that when things aren’t going our — or the global economy’s — way, we look to external forces as the cause, whereas we tend to attribute periods of prosperity to our own ingenuity and industriousness.

There appears to be at least one silver lining to economic downturns, however: Emory University psychologist Emily Bianchi found that young people who entered adulthood during a recession have lower rates of narcissism later in life, a finding attributed to a decrease in individualism and concomitant increase in collectivism that has been commonly observed in economic downturns. This could explain why the overall data on generational changes in narcissism appear unsettled: Pre-2008-recession Millennials’ glasses may be a bit more rose-colored than those of their younger comrades, affecting their beliefs and behavior.

Ultimately, the extent to which one’s temperament, principles, and conduct are bound up in birth year, and in political and social events that define a generation, can’t be precisely measured. Undoubtedly, some personal experiences weigh more heavily than collective ones, and vice versa. But the idea that birth cohort has a significant effect at all — that, even with the same genetic makeup and parents and peers, you would still be a different person if you had been born 20 years earlier or later — has compelling implications for psychological inquiry. Researchers continue to develop and refine methodologies for separating out the effect of generation in the hopes of inching ever closer to understanding not only our role in constructing the cultural fabric of our respective times, but also its role in constructing us. 

References and Further Reading

Bianchi, E. C. (2014). Entering adulthood in a recession tempers later narcissism. Psychological Science, 25(7), 1429–1437. doi: 10.1177/0956797614532818

Gentile, B., Twenge, J. M., & Campbell, W. K. (2010). Birth cohort differences in self-esteem, 1988–2008: A cross-temporal meta-analysis. Review of General Psychology, 14(3), 261–268. doi: 10.1037/a0019919

Glenn, N. (1980). Values, attitudes, and beliefs. In O. G. Brim, Jr., & J. Kang (Eds.), Constancy and change in human development (pp. 596–636). Cambridge, MA: Harvard University Press.

Giuliano, P., & Spilimbergo, A. (2009). Growing up in a recession: Beliefs and the macroeconomy (Working paper 15321). Cambridge, MA: National Bureau of Economic Research.

Konrath, S. H., O’Brien, E. H., & Hsing, C. (2010). Changes in dispositional empathy in American college students over time: A meta-analysis. Personality and Social Psychology Review, 15(2), 180–198.

doi: 10.1177/1088868310377395

Konrath, S. H., Chopik, W. J., Hsing, C. K., & O’Brien, E. (2014). Changes in adult attachment styles in American college students over time: A meta-analysis. Personality and Social Psychology Review, 18(4), 326–348. doi: 1088868314530516

Joyce, P. R., Oakley-Browne, M. A., Wells, J. E., Bushnell, J. A., & Hornblow, A. R. (1990). Birth cohort trends in major depression: Increasing rates and earlier onset in New Zealand. Journal of Affective Disorders, 18(2), 83–89.

Sutin, A. R., Terracciano, A., Milaneschi, Y., An, Y., Ferrucci, L., & Zonderman, A. B. (2013). The effect of birth cohort on well-being: The legacy of economic hard times. Psychological Science, 24(3),379–385. doi: 10.1177/0956797612459658

Twenge, J. M., Zhang, L., & Im, C. (2004). It’s beyond my control: A cross-temporal meta-analysis of increasing externality in locus of control, 1960–2002. Personality and Social Psychology Review, 8(3), 308–319. doi: 10.1207/s15327957pspr0803_5

Twenge, J. M., Konrath, S., Foster, J. D., Keith Campbell, W., & Bushman, B. J. (2008). Egos inflating over time: A cross-temporal meta-analysis of the narcissistic personality inventory. Journal of Personality, 76(4), 875–902. doi: 10.1111/j.1467-6494.2008.00507.x

Twenge, J. M., Gentile, B., DeWall, C. N., Ma, D., Lacefield, K., & Schurtz, D. R. (2010). Birth cohort increases in psychopathology among young Americans, 1938–2007: A cross-temporal meta-analysis of the MMPI. Clinical Psychology Review, 30(2), 145–154.

Trzesniewski, K. H., Donnellan, M. B., & Robins, R.W. (2008). Do today’s young people really think they are so extraordinary?: An examination of secular trends in narcissism and self-enhancement. Psychological Science, 19(2),181–188. doi: 10.1111/j.1467-9280.2008.02065.x

Trzesniewski, K. H., & Donnellan, M. B. (2010). Rethinking “Generation Me”: A study of cohort effects from 1976–2006. Perspectives on Psychological Science,

5(1), 58–75.

van den Berg, G. J., Lindeboom, M., & Portrait, F. (2006). Economic conditions early in life and individual mortality. American Economic Review, 96(1), 290–302. doi: 10.1257/000282806776157740

Yang, Z., Cao, F., Lu, H., Zhu, X., & Miao, D. (2014). Changes of anxiety in Chinese military personnels over time: A cross-temporal meta-analysis. International Journal of Mental Health Systems, 8, Article 19.

Xin, Z., & Zhang, M. (2009). Changes in Chinese middle school students’ mental health, 1992–2005: A cross-temporal meta-analysis. Acta Psychologica Sinica, 41(1), 69–78.