Happiness. To some people, the emotion feels like a nebulous concept. And while happiness itself is a subjective experience, the ways in which we can achieve it don’t differ all that much from person to person. In Science of Happiness, a 45-minute lecture currently playing on CuriosityStream—an online streaming channel dedicated to factual content on science, technology, civilization, and the human spirit—Nancy Etcoff, an evolutionary psychologist at Harvard, explores the roots of happiness and what we can do to help sustain it. Here are six of her findings. 

1. THERE’S A GREAT INEQUALITY IN HAPPINESS AROUND THE WORLD.

Environmental factors have an important impact on one’s happiness, which explains why there’s an inequality in happiness around the world. “We see here in the United States one of the highest levels of happiness,” explains Etcoff. “[And] in Scandinavian countries. We see parts of Africa [with] tremendous unhappiness … What we find is that circumstances mean a huge amount when people have very little. So if you have great poverty, if you have tyranny, if you have great inequality, these things are going to drag down happiness.”

2. PLEASURE AND DESIRE ARE AT LEAST PARTIALLY SEPARABLE.

While desire has long been thought of as a major trigger for happiness—you want something, you get it, you’re happy—Etcoff’s research with drug addicts suggests that the connection between pleasure and desire is not so straightforward. “If you look at the brain, you can actually see that pleasure and desire are at least party separable,” says Etcoff. “You can really, really appreciate and love something and not necessarily have that dopamine motivational drive to say, ‘I have to have it.’ You can have that dopamine, ‘I have to have it’—which all drug addicts have—and no longer enjoy the drug you’re taking. So you can have a hyper-want, which we often do in our culture; we think we really need the new house, the new job, [we’ve] got to get that person to fall in love with me. All of these things … if we don’t get that, we’re unhappy. And if we do get them—that new car, house, whatever, more money—we’re going to be happy. [Which is] not necessarily [true]. We go into that hyper-wanting state and it becomes more and more divorced from our sense of what really gives us pleasure.”

3. FRIENDS INSPIRE MORE HAPPINESS THAN FAMILY MEMBERS.

According to Etcoff, social bonds are essential to personal happiness. “People tend to be happiest when they’re with friends, relatives, and spouses,” says Etcoff. And in that order. “Children are a little bit lower. Being alone, people don’t like it as much. And, unfortunately, being with the boss is the worst. It’s worse than being with clients or being alone. But social bonds that you enjoy have profound effects on not only your well being, but your general sense of safety and calm in the world.”

4. HAPPINESS HAS MANY POSITIVE SIDE EFFECTS.

Among the research that Etcoff cites in her lecture is Jeffrey Sachs’ World Happiness Report, which found that happiness offers several positive side effects. “Happy people live longer, are more productive, earn more, and are also better citizens,” says Etcoff. “Well-being should be developed both for its own sake and for its side effects.”

5. HAPPIER PEOPLE ARE HEALTHIER PEOPLE.

The positive effects being happy has on one’s health is not something that should be overlooked, according to Etcoff. “The positive emotions have effects on health over and above the negative effects we know of in depression and stress and anger,” she says. “With disease, we find that positive emotions have their own effect; people who have positive emotions live longer, they live better, and they’re healthier. They have greater resistance to common infections, decreased loss of function and mobility in older adults, and more and closer social ties.”

6. HAPPINESS IS CONTAGIOUS.

Smile—it might be contagious. “We catch emotions from one another,” says Etcoff, who references the Framingham Heart Study in her lecture. “We’re seeing ourselves much more as part of a whole … What’s fascinating here is that your happiness impacts your friend’s happiness, [which] impacts your friend’s friend’s happiness, whom you may never have met, [which] impacts your friend’s friend’s friend’s happiness. Happiness and emotions radiate.”