You undoubtedly have heard it said that “a leopard can’t change its spots” when it comes to the idea that personality is fixed early in life. Perhaps you’ve hoped that your contrarian in-law will become nicer and more fun to be with if you just wait long enough. However, with this belief in personality’s rigidity, you figure the odds are low that this might happen.

Let’s contrast this set of assumptions with the evidence you have from your own life. You think back on what you were like in your youth and realize that you’re no longer as reckless and carefree as you were back then. Or maybe you’ve become more of a risk-taker. Either way, you have changed. Why, then, couldn’t your cranky relative?

Researchers documented nearly 20 years ago that personality can and does change, at least in terms of the Five Factor Model (FFM) Traits (conscientiousness, openness to experience, agreeableness, neuroticism, and extraversion; Roberts et al., 2006). The name of the game in the field next became one of finding out why. Is there something intrinsic in a person that simply shifts with the passing of the years, or are there specific instigators of change in the form of life events?

And if change is the result of experiences, which ones matter the most? Did your riskiness (conscientiousness) levels go down because you had to buckle down to life’s responsibilities, or would they have gone down anyway? Or, if you became more adventurous, was it because you went on a vacation and decided to go bungee jumping?

A new study by University of Illinois at Urbana-Champaign’s Keely Dugan and colleagues (2024; online publication occurred in 2023) used a novel approach to contrasting the effects of important versus seemingly minor events on personality change. The 4,904 adults (average age 35........

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