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We talk about personality as something that requires self-discovery. We travel and have new experiences to “find ourselves,” as if our selves have already been determined, and an epic trip to Europe will help us better understand what’s already within us. But what if that’s not how this works? What if personality is fluid, determined not just by nature and nurture, but also by the things we do? And what if, during your travels, you’re not so much finding yourself as you are creating yourself?

University of Cambridge psychologist Brian R. Little explores these questions both in his research and in his new book, Who Are You, Really? “We have moved beyond the old nature versus nurture debates,” Little said. “Because there are social influences that influence genetic expression and biological factors that can influence how we shape our social worlds.” It’s not either-or; instead, nature and nurture interact.

But beyond that, Little argues that the things we do can influence our nature and nurture, too, in order to shape our personality. According to his theory, it’s possible that actions such as travel, taking care of pets, or even going to parties can change who you are. You’ve probably heard of the Big Five personality traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism. Chances are, you know which of these traits apply to you, from observing yourself over the years. If you’re neurotic, for example, you’ve probably analyzed your social interactions as far back as you can remember and know that you have an unshakable habit of staying up at night, worried about that possibly dumb thing you said in a meeting earlier that day.

But Little believes there is more flexibility to personality than we might assume. Here’s an overview of what he means.

You’re not trapped by your own personality traits. A shy person can become charismatic and a loud person can become a listener, when met with adequate reason to do so. As an example, Little pointed to comedians Robin Williams and Mike Myers, both of whom described themselves as introverts. But they’re also what Little would call “site-specific” extroverts, meaning that they were able to be gregarious and outgoing onstage. Comedic acting allowed them to grow their personality beyond the standard label of “introvert.”

Little would call this an example of a “personal project,” by which he means the goals, tasks, and actions that you take on in your personal life. Whatever they are, they must be meaningful to you; they must also be deliberate, in that you choose to tackle it. Take someone who is typically agreeable, Little said, who becomes “assertive, domineering, and pugnacious” when she needs to be, such as when she’s battling with administration at an eldercare facility regarding her ailing mother’s needs. Just because you’re naturally nice doesn’t mean you always have to be.

Acting against your nature doesn’t mean you’re being “fake.” When you act out of character, it allows you to build upon your personality so that you can learn how to be both quiet and gregarious, when context calls for it. Acting out of character allows you to be “an alternative you — in a sense, perhaps, an optimized you,” Little writes. But it’s still you.

In high school, I joined the debate team. I asked my friends for advice when I had to give my first speech, and one of them told me, “Just be yourself.” The problem with this standard advice was that “being myself” meant being shy and awkward, to the point where another friend advised, “Definitely don’t be yourself.” I took my second friend’s advice, and went against my nature to give a high-energy, bold speech that was completely out of character for me. As a teenager, I called it acting, and I learned to “act” when I gave future speeches, when I interviewed for jobs, and much later in my career, when I gave media interviews. So was it all an act?

Maybe life would would be better if you didn’t think of you as a fixed concept.

Not quite. Authenticity is not that simple. “We have, in my judgment, three different ways of ‘doing authenticity,’” Little said. We are authentic and true to our biogenic personality, the personality that’s determined by nature and comes instinctively to us, but there’s also sociogenic authenticity — that is, “when we act with fidelity toward the cultural and social codes that we have learned,” Little said. I was being myself when I gave that speech; it was just a different approach to myself. Over the years, this professional persona became part of my personality.

“‘Idiogenic authenticity’ is the term I give to showing fidelity to the core projects in our lives,” Little said. “These may be in conflict with biogenic and sociogenic aspects of ourselves, but they signify a kind of authenticity that helps explain much that is noble and creative about human beings.” In other words, we’re complicated. We have multiple ways of “being authentic.” When you have to stick to a fixed idea of your sense of self, you limit your potential for growth. Also, developing new personality traits isn’t necessarily about replacing old ones; it’s about pushing against them to build new traits.

You can’t pick just any personal project. Let’s say you’re a loud, talkative person with a tendency to shoot from the hip. You want to be more empathic with people and learn to listen better. It would make sense to find a personal project that forces you to take on those desired traits, maybe volunteering at a homeless shelter, reading op-ed columns, or attending lectures. Or let’s say you’re a conscientious person focused on your career, and you want to be more of a caretaker. You might volunteer at a nursing home or get a small pet to help build that trait.

The key to whether or not this works, Little believes, is you, and how sincere your interest is. If, he explained, you “initiate a self-change project or have enthusiastic buy-in to it, the project is likely to be successful.” If, on the other hand, it’s something someone else is making you do, or even simply if your heart isn’t fully in it, it’s less likely to work. If you want your personality change to stick, the project you choose has to excite you. For instance, if it’s your goal to read more op-ed columns, but you can’t bring yourself to care about politics, this particular personal project might not be sustainable.

But you can always revert back to your comfort zone when you need it. If your personal projects are too overwhelming because they veer too far from your personality, it’s fine — necessary, even — to take a break. Little calls this a “restorative niche,” an activity that lets you reconnect with your biogenic self — your natural self, if you will. It also allows you to avoid burning out on your project. If your goal is to attend conferences to become more sociable, all that socializing might become overwhelming. Scheduling some time to head back to your hotel room and listen to music could be a great restorative niche.

So why would you want to override your personality? Aside from helping other people or becoming the best version of yourself, there’s a case to be made for well-being. “Surprisingly enduring happiness can ensue as a side effect of those kinds of projects,” Little said. “The sustainable pursuit of core projects in our lives is the hallmark of human flourishing. And one way of looking at our personalities.” Maybe life would would be better if you didn’t think of you as a fixed concept. Little quotes the psychologist George Kelly: “A good deal is said these days about being oneself … I suppose what is meant is that one should not strive to become anything other than what he is. This strikes me as a very dull way of living.”