Teenagers can be a real handful—rebellious, impulsive, selfish, manipulative.  At times it’s hard to recognize the adorable children that they were just a few years before. But all is not lost. In a recent research project with Wiebke Bleidorn and Jason Rentfrow, I analyzed personality data from more than 1.1 million people from all around the world and found that, as people grow older, they mellow out and become more socially mature. Until they retire, that is.

But let’s back up a little. Our personalities not only define who we are but also influence virtually all important things in our lives—including what kind of jobs we do (and how successful we are at them), who we date and marry, what we spend our money on and how much of it we save, and when and how we die. For many years, psychologists believed that personalities are set like plaster: once a rebel, always a rebel. But, in the past 10 years or so, a fast-growing number of studies, often with large samples and longitudinal data, have shown  that it is not quite as simple as that. Rather, when it comes to personality across the lifespan, we see both stability and change in people’s characteristics.

Importantly, almost all studies that have investigated personality development across the lifespan have looked at neutral or positive traits, especially the Big Five personality traits—agreeableness, conscientiousness, extraversion, emotional stability, and openness to experience. Meanwhile, nobody had looked at developmental trends in the dark side of personality.

To change this, we partnered up with TIME Magazine to run an online study that reached more than 1.1 million people worldwide. In doing so, we had a little help from Harry Potter—but that is a different story. Suffice to say, the study was fairly popular and produced a large dataset on several personality characteristics, including Machiavellianism, which refers to manipulative personality. Machiavellianism is named after the 16th century Italian diplomat, Niccolò Machiavelli, who unapologetically advocated the use of deceitful, immoral, and cruel behaviors as a way to maintain political power. Psychologists became interested in this trait when they realized that Machiavelli’s advice is still alive and kicking, and ordinary people today act in manipulative, deceitful, and underhanded ways to varying degrees in their daily lives. So here we had our dark trait.

Using people’s individual scores on a measure of Machiavellianism, we charted how Machiavellianism differed across age groups in our sample. As we had at least 1000 participants for every age-year between 10 and 67, we could look at fine-grained differences in how Machiavellianism changes with age.

Here’s what we found:

  1. As people enter puberty, they become more reckless, cunning, and exploitative, with peaks in Machiavellianism at age 16, at the height of adolescence.
  2. Thankfully, this appears to be only temporary, and as people transition into adulthood, they largely shift back toward greater decency, kindness, and sociability. According to social investment theory, one important trigger for this personality maturation involves the demands and expectations of new social roles that come with adulthood, such as entering the work force, marrying, and becoming a parent. As people solidify their identities and social roles, this trend toward lower Machiavellianism continues throughout adulthood until people’s mid-sixties, when Machiavellianism reaches its overall low point if life.
  3. But then—perhaps surprisingly—right after age 65, we see a steep uptick in Machiavellianism. There is little research on this, and our data do not speak to any age trends past 67, so we can only speculate about what might lead people to become more Machiavellian after 65. Of course, 65 is a common marker for retirement in many countries, so one possibility is that, once they stop working, people no longer need to be as nice as before, or perhaps they no longer have the energy to be nice. But the all-time low in Machiavellianism at age 65 could be just an outlier that reflects the initial excitement that comes with the freedom of retirement, and people bounce back to their usual Machiavellianism levels after that.
  4. Women are nicer—period. Although men and women both experience the fluctuations in Machiavellianism described above, at every age women score lower on Machiavellianism than men.
  5. Being an a***** can pay off. Notwithstanding these age-related trends, which can be found across all income-groups, throughout the lifespan, people who earn more money consistently show higher levels of Machiavellianism than those with lower incomes.

Taken together, if you have teenage kids, or are a teenager yourself, don’t worry: for all we know, you will be fine. When it comes to Machiavellianism in old age, however, we still know fairly little, and more work needs to be done. That being said, In the meantime, you might want to keep an eye on grandpa.

For Further Reading

Götz, F. M., Bleidorn, W., & Rentfrow, P. J. (2020). Age differences in Machiavellianism across the life span: Evidence from a large‐scale cross‐sectional study. Journal of Personality, 88, 978–992. doi:10.1111/jopy.12545

Paulhus, D. L., & Williams, K. M. (2002). The dark triad of personality: Narcissism, machiavellianism, and psychopathy. Journal of Research in Personality, 36, 556–563. https://doi.org/10.1016/s0092-6566(02)00505-6

Roberts, B. W., & Mroczek, D. (2008). Personality trait change in adulthood. Current Directions in Psychological Science, 17, 31–35. https://doi.org/10.1111/j.1467-8721.2008.00543.x

Soto, C. J., & Tackett, J. L. (2015). Personality traits in childhood and adolescence. Current Directions in Psychological Science, 24, 358–362. https://doi.org/10.1177/09637 21415 589345


Friedrich M. Götz is currently writing his doctoral dissertation in psychology at the University of Cambridge. He is glad that most of his own encounters with Machiavellianism happen only when he is analyzing his research data.