After reading online about Invisbilia’s latest episode on “The Personality Myth,” I decided to listen to the episode myself to see if the reactions from fellow personality psychologists were hyperbolic. In short, they were not. Chris Soto and Simine Vazire already have excellent, succinct explanations of the flaws of this episode. I also wanted to add my own somewhat longer response as someone who has researched both the stability and change in personality.

This episode of Invisbilia covered one side of the person-situation debate—the argument that personality is inconsistent, so therefore it doesn’t exist. The person-situation debate actually ended in a synthesis of the ideas—personality is relatively consistent over time, but it can also change across different situations. How? Imagine this exercise—let me ask you how extraverted you are right now. How about a few hours from now? Tomorrow morning? And the next day? When you ask people to answer how extraverted they are several times a day for two weeks, you get a better idea of their whole personality trait, which looks like a bell curve (or a distribution). Sometimes people are very extraverted in a situation, sometimes people are less extraverted in another situation, and the average level of all these different snapshots reflects a person’s trait. When you think of a personality traits in this way—as a distribution of how you are across situations—you can see how people are the same over time (the average of two weeks of these measurements) and how they change in different situations. You have a default, trait level, and situations (or stuff going on in your mind) can cause you to fluctuate around this average trait level.

Once you think of personality traits this way, you can start to try to understand why people change in different situations. People don’t just change at random—there are distinct patterns that can be studied. My work has looked at the goals that people are pursuing in a given moment—and we found that a huge part of these changes in extraversion and conscientiousness in a given moment are the specific goals people are pursuing. When you’re trying to have fun, connect with people, or make others laugh, you are more extraverted. When you are trying to get things done or use time effectively, you are more conscientious. We also did an experiment and an observer study that shows the same pattern of results.

This overview explains personality changes over a few days and hours, but what about changes over the years? How do people change over long periods of time? The Invisibilia episode talked about Dan, who said that he made a conscious decision to change who he was over a period of time. Personality development is complex, but it does develop and change over the lifespan. The most volatile time for this change appears to happen in young adulthood–when people have new experiences and social roles (e.g., go to college, start our first job, get married, etc.). We also have evidence that suggests that personality may change as a part of therapy treatment. Still, long-term change doesn’t appear to be drastic or quick, which echoes how Dan describes that it took a long time for him to change his personality.

Ultimately, our behavior is complicated, and it is a mixture of personality and situations. It is something we have known for a long time–Kurt Lewin famously made this case back in the 1930’s–but we now have technology to study personality in more complex ways, faster and easier than ever before.

Some might ask why we personality psychologists had such a strong reaction to this episode. The answer is in the podcast itself, when Walter Mischel casually mentions that he was accused of nearly destroying the field of personality. This claim alludes to the fact that the number of personality psychologists declined drastically in the 1970’s, both in terms of number of graduate students studying it and the number of universities hiring people who studied personality. Even today, personality psychology graduate programs are limited in the United States. To add insult to injury, we still have to defend why the thing that we spent years studying in graduate school actually exists and why it matters. So yes, personality psychologists may have a slight chip on our shoulders, but for good reason. Episodes like the one Invisbilia just aired does not help our situation, pun intended.

To see a modern view of Walter Mischel’s Personality and Assessment, the Journal of Research in Personality did a special issue in 2009 on its 40th anniversary called “Personality and Assessment at Age 40: Reflections on the Past Person–Situation Debate and Emerging Directions of Future Person-Situation Integration – Personality and Assessment at Age 40.” It is worth reading these articles to get a more up-to-date sense of the person-situation debate in the decades that followed.