How a Colby Professor is Helping to Shape Personality Research
Professor of Psychology Chris Soto receives a prestigious award from the European Association of Personality Psychology
Teaching math to middle schoolers is, famously, not for the faint of heart. But that’s exactly where Chris Soto found inspiration that launched him into a noteworthy career in psychology and personality research.
When Soto was in college, he had learned about the Big Five personality traits, a group of characteristics used to study personality. At that time, the conventional wisdom was that personality was very much an adult phenomenon, with some psychologists adhering to an old belief called the “plaster hypothesis.” That is, in adulthood, a person’s personality sets like plaster and will never soften again.
But that’s not what Soto—now a professor of psychology—saw in his middle school classroom.
“It was very clear to me just from hanging out in middle school for a couple of years that you can see versions of the Big Five personality traits in 13 and 14 year olds,” he said. “It was also pretty clear that kids were changing with time.”
Soto, galvanized, left behind fractions, algebra, and percentages and headed for graduate school at the University of California, Berkeley, where he received his doctorate in personality psychology.
Since then, he has become an expert in the field. He and a colleague worked to develop the Big Five Inventory-2, a comprehensive tool that assesses the Big Five traits and has been translated into more than 40 languages since its publication in 2017. The BFI-2 is considered to be a foundational resource in the field of personality psychology. Soto has also played an important role in advancing understanding of how personality traits develop and change across a person’s life.
In recognition of these and other contributions, Soto, who also serves as the director of the Colby Personality Lab, has been named the 2025 recipient of the prestigious European Association for Personality Psychology’s Mid-Career Award. This award is given once every two years to recognize someone whose work has had a significant impact on the field of personality psychology. His nomination letter highlighted the ways that his work has shaped key areas of the field, including personality assessment, lifespan development, and the prediction of life success.
“It was an honor and a big surprise,” he said of receiving the award.
About the Big Five
The quest to understand personality, or how a person thinks, feels, and behaves, is an enduring one. Nearly 2,400 years ago, the Greek physician Hippocrates developed the first known theory of personality types based on the “four humours:” sanguine, choleric, melancholic, and phlegmatic.
Today, it can be hard to find a person who hasn’t spent some time taking personality tests online, in magazines, or even on job applications and in the workplace. A lot of those tests may be diverting, but the BuzzFeed “Which Disney Princess Are You” style of quiz is not exactly scientifically sound.
Soto’s work, grounded firmly in personality psychology, is different.
The Big Five personality traits, a widely researched and accepted psychological framework for understanding personality, were first identified in the 20th century. In 1936, two psychologists listed 4,500 terms to describe personality differences. In the ensuing decades, those were narrowed to five primary traits. Those are extroversion versus introversion, agreeableness versus antagonism, conscientiousness versus impulsiveness, neuroticism versus emotional stability, and openness to experience versus closed-mindedness.
“It has been the most prominent conceptual model of personality traits in personality psychology since the 1990s,” Soto said. “We’ve continued to learn more about the model over time and how more specific traits within the broader Big Five domain can be broken down. And we’ve developed tools for measuring all those things.”
One of those tools is the Big Five Inventory-2, which Soto created with Oliver John, his advisor at UC Berkeley. John had published one of the first Big Five personality tests in the 1990s, and about a decade ago, the two personality psychologists updated the inventory to better reflect what is now understood about the Big Five personality traits.
“It’s been adapted into more than 40 languages and different cultural contexts around the world. And it really does seem to have become the gold standard for measuring the Big Five.”
Professor of Psychology Chris Soto on the Big Five Inventory-2
“I’ve been really surprised at just how much it has taken off,” Soto said. “It’s been adapted into more than 40 languages and different cultural contexts around the world. And it really does seem to have become the gold standard for measuring the Big Five.”
Lessons from the middle school
In his middle school classroom, it was easy to spot students who were highly extroverted, or agreeable, or antagonistic, just to name a few of the traits exhibited. Soto wanted to find out more about how and when personality traits develop, and researched this in graduate school.
“We found that, yes, you can clearly see the Big Five personality traits as young as 5 years old,” Soto said. “Basically, as soon as kids have a school environment and social relationships with peers, you can see all these different things come out.”
One of their findings likely sounds familiar to anyone who has known, or been, an early adolescent: that a person’s nadir of agreeableness and conscientiousness takes place between ages 10 and 13 or 14.
Soto jokes about this with the students in his introduction to psychology course.
“‘Let’s all take a moment to feel sorry for your parents and your teachers who had to deal with you at your lifetime peak of meanness and laziness,’” he tells them. “‘But the good news is that you’ve probably recovered from there, and also that you’re probably going to gradually keep becoming more agreeable and more conscientious over the next couple of decades.’”
Some of those students go on to work with Soto as research assistants at the Colby Personality Lab, where they help conduct research into personality structure, lifespan personality development, and personality and life outcomes. The lab’s busy website can see visits from hundreds of people a day who stop by to take or learn more about the Big Five Inventory-2 and other resources, including the Behavioral, Emotional, and Social Skills Inventory (also known as the BESSI).
The professor’s enthusiasm for his subject is unmistakable, according to Hannah Shammas ’28, a psychology major who took Soto’s personality psychology course this spring.
“It was special to see how personally invested [Soto] is,” she said. “You can really see his passion when he talks about the Big Five, and that energy makes the material a lot more engaging and exciting to learn.”
The ‘soft plaster’ hypothesis
Much of Soto’s research is aimed at learning more about how a person’s Big Five personality traits are connected to their life outcomes, including academic, occupational, health and well-being, and social relationships. One effort to do this included having a representative sample of 3,000 American adults and adolescents take the Big Five Inventory-2 and then evaluate different kinds of life outcomes to see what the results would be. Overall, they found that about 90 percent of the hypothesized links between traits and life outcomes were statistically significant.
For example, conscientiousness is a big predictor of academic, work, and health outcomes—a person who is lower in this trait is more likely to engage in risky behaviors, less likely to go to a doctor, and less likely to follow through on a health plan.
But not necessarily.
“The general pattern is that personality traits become more stable with age, and change less, but they never completely stop changing. They never become set in stone,” Soto said. “The current consensus is more of what’s called the ‘soft plaster’ hypothesis: that traits thicken, and don’t change as much, but even in middle age and later adulthood, you see some mean level changes in personality traits.”
Some of those changes seem to occur naturally as a result of life experience. If a person gets in trouble with their boss for being late to work, they can alter their behavior so that they get to work on time.
“And then there’s a chance that it will trickle over and affect how you behave outside of your job, too,” Soto said.
For Anja Franck ’27, a psychology major, it was illuminating to learn in class how personality traits reverberate throughout a life.
“I learned how our personality can impact our relationships, our work interests, and our extrinsic and intrinsic motivations, and our success,” she said. “I think it’s just very applicable to day-to-day life, and I think it’s really cool.”
A path towards change
A newer theory is the idea of intentional personality change, that a person can set goals to change their personality traits. It’s become a hot topic of study in the last five years or so, and the preliminary evidence is encouraging.
“It’s not the case that everybody changes in the way that they want to, but it’s better than a 50/50 coin flip,” Soto said.
He’s found that the best approach seems to turn abstract goals into more concrete, specific intentions. For an introvert, this could mean identifying what it would actually look like to act in a more extroverted way in certain situations, then setting specific goals to practice doing this over time.
“If you have people go through that process over the course of a few months, it further increases the chances that they’re going to actually change in the direction that they want to,” Soto said.
To find an example, he only needs to look at himself, a self-described introvert who has had to work at public speaking.
“When I started out, I was terrible because it did not come naturally to me,” Soto said. “But at this point, I’ve had nearly 20 years of practice, and I’m now at least decent. Much better than when I started. It’s not that I’ve turned from an introvert to an extrovert, but I have developed those skills that I can bring out and use when I really need them.”
