The difference between introverts and extroverts was perhaps best captured by Jonathan Rauch in a 2003 Atlantic essay that's since taken on a life of its own. Introverts, Rauch writes, "are people who find other people tiring." They're not necessarily shy or misanthropic, but rather enjoy solitary time. Extroverts, meanwhile, "are energized by people, and wilt or fade when alone," he writes. "They often seem bored by themselves, in both senses of the expression."
However bored extroverts might be by themselves, they tend to be a cheerier bunch on the whole. Time and again, in study after study, behavioral scientists have found that extroverts report themselves on well-being surveys as happier than introverts do. (In fact, introverts report more happiness when they act like extroverts, though they fail to anticipate this emotional kick-back.) The finding has proven so strong that some researchers believe positivity could rest at the core of what makes an extrovert an extrovert.
Recently, in an attempt to understand this link better, psychologists Wido Oerlemans and Arnold Bakker recruited more than 1,300 people to keep detailed track of their daily activities and describe their feelings at the time. All told, the researchers gathered data on nearly 14,000 activities across some 5,600 days. Meanwhile, the personalities of the participants were evaluated for their place on the introvert-extrovert continuum. (Nobody is purely one or the other.)
Like most researchers before them, Oerlemans and Bakker found a strong correlation between happiness and extroversion. But they discovered that this link largely depended on what type of task a person was doing. Extroverts did report themselves happier than introverts on so-called "rewarding" activities: paid work, for instance, or exercise. However, there was no happiness difference between introverts and extroverts on mere "pleasurable" activities, such as watching television or relaxing or shopping. Meanwhile, to no one's surprise, extroverts also reported greater happiness than introverts while doing activities with others, compared to doing them alone.
Together the findings—reported in the Journal of Research in Personality—suggest that the pursuit of rewards, combined with general sociability, go a long way toward explaining why extroverts are happier in the moment then introverts. "Thus, high extroverts react more strongly to situations that are either rewarding, social, or both," Oerlemans tells Co.Design. Since extroverts tend to spend more time on these rewarding activities than introverts, as well as more time with others, it's not hard to see why they spend more of their lives feeling happier.
Still, the story isn't perfectly clear. The extrovert-happiness link persisted even when Oerlemans and Bakker controlled for the extra time extroverts spend doing the things that make them happy. This means additional factors—likely innate—are playing a role in shaping the introvert disposition. "This invites further biological research," Oerlemans says, "that examines where such higher levels of [positive affect] come from in the first place."
Some previous research offers clues to what those biological factors might be. A 2005 neural imaging study, for instance, found that extrovert brains have a stronger response to rewards—especially in the amygdala (an emotional center) and the nucleus accumbens (part of the dopamine system). The heightened response was also linked to test participants with a gene known to crank up dopamine responsiveness. To some extent, extroverts seem wired to enjoy life's rewarding moments, from playing to partying, in a way introverts are not.
What's often lost in the discussion of extrovert happiness is the fact that happiness itself is difficult to both define and measure. Susan Cain, author of Quiet: The Power of Introverts in a World That Can't Stop Talking, once outlined several "alternative" forms of happiness that introverts experience but extroverts may not. These include the silent bliss of solitude, the occasional comfort of sadness, and the thrilling flow of intense thought—concepts of happiness not always captured on traditional surveys of well-being.
It's also quite possible that introverts and extroverts have a different way of quantifying similar emotional experiences. An extrovert prone to enthusiasm might call a rewarding activity "the best thing ever," while an introvert prone to reservation might call it "very enjoyable." Does that mean the two people truly feel different levels of happiness in the moment, or just use different scales when rating their feelings? Rauch laments that many social etiquette books were "written, no doubt, by extroverts"; maybe some basic happiness questionnaires are, too.