The answer to this twisted riddle may be the key to what most people are searching for, according to Emory psychiatrist Gregory Berns. In his new book, Satisfaction: The Science of Finding True Fulfillment, Berns explores the effects of various human behaviors on the brain, with some surprising conclusions.

Most of us operate on the assumption that we’re in pursuit of happiness, a feeling of pleasure and contentment. But Berns draws a critical distinction between happiness and satisfaction.

“Happiness and pleasure are passive emotions that come from things that happen to you,” he says. “Our notion of happiness is by and large due to genetics and luck. But satisfaction is a positive emotion you experience because of things you make happen yourself.”

The two main ingredients of a satisfying experience, according to Berns, are novelty—the unexpected—and challenge, or what has been called “good stress.” Although running a hundred-mile ultramarathon may sound like hell on earth to some of us, such demanding, unpredictable activities require a level of focused attention that taps into the reward system of the brain. That’s different from the pleasure system, Berns says.

New or surprising stimuli, Berns found, release the feel-good neurotransmitter dopamine in an area at the top of the brain stem called the striatum. Dopamine is what gives us our sense of purpose and causes us to commit to a particular course of action over another, from an act as deliberate as kicking a ball to one as absentminded as scratching your nose or glancing up from a book. It’s also where motivation comes from.

“Motivation and commitment are two facets of the same process, with dopamine acting as the catalyst that begins the process,” Berns writes.

The other neural piece of the satisfaction pie is cortisol, the hormone that’s released in response to stress. Cortisol has gotten a bad rap from researchers because of its association with the sort of high-level stress that can lead to heart disease and high blood pressure. But Berns suggests that cortisol has a bright side, particularly when combined with dopamine.

“A lot of people say cortisol is bad for the brain, but in my opinion, they haven’t looked at the positive effects,” he says. “If you give people cortisol, they become giddy. It has mood-elevating qualities.”

So how to extract this winning combination from humdrum everyday existence? It’s not as hard as you might think, Berns says. Varied physical exercise, a special meal, finishing a crossword puzzle—all can provide the little jolts of brain-chemistry delight that produce a feeling of satisfaction.

Berns describes sharing a lunch of roast duck, cold champagne, and freshly baked chocolate torte with a master chef: “A satisfying dining experience goes beyond mere sustenance. It transcends taste, too, for even with the best ingredients, you need something else—something novel.”

Berns’ use of first-person adds a layer of depth and narrative flow that gives readers a window onto how the search for satisfaction deeply affected a real person: Berns himself. In the final chapter, he tackles the challenge of finding satisfaction in long-term relationships, including his own marriage. While one might assume that the need for romantic novelty means infidelity and multiple sex partners, Berns comes to the conclusion that you don’t need new people to find newness in relationships. In fact, long-term, committed relationships may be our best source of novelty and satisfaction—as he and his wife of fifteen years discovered.

“No source of novelty can exceed that created between people who truly, deeply trust each other,” Berns writes. “The freedom and trust to do novel things in a natural way makes sex creative and complex.”

For Berns, neuroscientific research evolved into an intense personal quest. He found he was “trying to build a philosophy based on biology.”

The philosophy: “Stop pursuing happiness,” Berns says. “Pursue satisfaction, in terms of trying, learning, and doing new things.”—P.P.P.