What Really Shapes Your Personality Throughout Your Life

Generational labels about people’s personalities abound in popular psychology. There’s the “entitled Millennial,” the “cynical Gen-X’er,” and—of course—the “selfish Baby Boomer.” Actually, the “baby” is usually left out completely and the millions of people born between 1946 and 1964 (or so) are just referred to as “Boomers.” You may not even be aware that you’re using these labels because they have become so ingrained in common parlance.

Of course, if you are a member of any of these generations, you probably resist having the corresponding label apply to you. Quite likely, you become annoyed when someone says “OK, Boomer” if you are of that generation (or even, preferably, if you're not). You know from your own experience, and that of your age peers, that you can’t be so easily categorized, and even more to the point, treated as someone worthy of disdain.

Unpacking Age and Generation as Influences on Personality

The next time someone uses one of these derogatory generation-based terms, new research will now provide you with the evidence you need for a snappy comeback. The results of one of the most comprehensive studies of adult developmental change ever conducted are now hot off the press, providing long-awaited findings about how personality is influenced by your year of birth.

University of Hamburg’s Naemi Brandt, along with University of Washington’s K. Warner Schaie and Sherri Willis, the principal investigators of the study (2022), titled their investigation of generational differences in personality with the somewhat rhetorical question: “Acting Like a Baby Boomer?” Their data, based on the groundbreaking 70-year investigation known as the Seattle Longitudinal Study (SLS), made it possible for the research team to tease apart carefully and methodically the potential contributions to personality change of social factors associated with the historical time from the ticking off of the years according to the individual's inner psychological clock.

Although it’s simple to understand the root problem in studying personality change over time, it’s quite another matter to conduct that careful teasing apart of social versus personal change. Consider what happens to you as you change over your own life. You may experience personality growth that comes from within, but you are also subject to the forces of history. You can't be plucked out of the context in which you get older, so there is no way to see how you would change independently of these historical influences. Complicating matters further, historical change affects everyone, but might it have differing effects depending on your own age?

Now translate this thorny theoretical knot into practical terms as you think about how you’d study this problem. The SLS researchers did so by separating their analysis into three basic factors. The first, called intraindividual change, would be what you might logically think of as the changes within you that take place over time, and was indexed simply by the length of time a person was in the study. Second, your chronological age is simply your own age at the moment. Third, and this is key to understanding generational differences, is your cohort or year of birth.

With personality data divided into these three metrics, the researchers could look at whether people changed within themselves over time, varied as a function of their age alone, or showed effects specific to their cohort. If the baby boomers were going to have anything unique about their personalities, then it should show up as a significant cohort effect overriding the influence of time or age.

Were the Generations Really All That Different?

For the 2022 analyses, the SLS research team had at their disposal 4,732 participants averaging 53 years old (53 percent female) whose age when first tested ranged from 19 to 91 years. This sample yielded a massive 12,000 separate pieces of personality data over the course of the study. Because the SLS originated in 1955, this meant that the so-called Baby Boomer generation itself was actually the youngest in the sample. The two older generations were born between 1883-1913 and 1914-1944. Indeed, even the youngest generation went several years beyond the traditional Baby Boomer designation, with birthdates ranging from 1945 to 1976. Technically, then, they were “Baby Boomer Plus.”

To measure personality, Brandt and her colleagues relied on the Five-Factor Model (FFM) with its traits of openness to experience (O), conscientiousness (C), extraversion (E), agreeableness (A), and neuroticism (N). Because the researchers didn’t have at their disposal any of the contemporary FFM measures from the early days of the study, they cleverly retrofitted the personality scale they began with into the FFM, providing them with a reasonably good approximation of the measures currently in use.

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You can get a feel for this personality measure by seeing how you’d rate on the following items:

O: For most questions, there is just one right answer once a person is able to get all the facts (reverse-coded)

C: I am known to be a hard and steady worker.

E: It is very hard for me to act natural when I am with new people (reverse-coded).

A: If I get too much change in a store, I always give it back.

N: I am often sorry because I am cross and grouchy.

Turning to the findings, after constructing data curves for each FFM trait across each age (within-person change) and cohort, the authors were able to pick apart those generational trends. Rather than showing a clear effect of any of the three key factors, the evidence turned out to be, in the words of the authors, “mixed.”

The most interesting question from the standpoint of how age and generation combine to influence personality was whether the curves over time would differ by birth cohort. Although the authors reported that there were some cohort differences in personality traits, on this key issue, “evidence regarding cohort-related differences in developmental trajectories was weak.”

The only effect that stood out at all was that members of the Baby Boomer Plus generation were more likely to increase over time in the one personality trait of agreeableness. However, this was because they started out with lower agreeableness to begin with, giving them more room to grow. In addition, members of this post-World War II generation went to college and therefore entered the job market at an older age than did their parents and grandparents. As a result, these later-born cohorts were sowing their wild oats in college rather than dealing with the exigencies of holding down a job and family. Even by the age of 55, these early life experiences shaped them to the point that they hadn’t quite caught up in agreeableness to the generations of their predecessors.

How to Use The Findings to Ward Off Those Generational Labels

It's true, then, that the Baby Boomers showed one quality unique to their generation, compared to those who came before them. However, would you really want to hang your hat on such a small and completely understandable blip in the data?

Here, then, is your retort to those who would label your personality by your year of birth. In fact, why not cite the authors themselves? In their words, “This work helps us better understand how societal change can shape what people need, value, and desire, and they refute overly generalized stereotypes that stigmatize people born at specific historical times.”

You don't have to be fighting only the Baby Boomer stereotypes to rely on these findings. Given the careful statistical procedures invoked by this highly esteemed research group, it is reasonable to predict that future studies will continue to challenge a one-size-fits-all generational label. Yes, it's possible that people of different ages are affected differently by different historical periods, but this doesn't mean that everyone born in the same calendar year or group of years will react in precisely the same way.

To sum up, personality change can occur in a variety of ways for a variety of reasons. Finding your own fulfillment as your traverse your adult years can be a matter of expressing your individuality regardless of the time in history when you happened to be born.

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