Richard is an ambitious 36-year-old white commodities trader in Florida. He’s healthy and drop-dead handsome, lives alone in a house with a pool, and has worked his way through a series of gorgeous women. Richard’s job is stressful, but he spent Christmas in Tahiti. Unencumbered, he also has time to indulge such passions as reading (right now he’s finishing a book called “Half the Sky”), marathon running and writing poetry. In the last few days, he has been composing an elegy about the Haiti earthquake.

Lorna is a 64-year-old black woman in Boston. She’s overweight and unattractive, even after a recent nose job. Lorna is on regular dialysis, but that doesn’t impede her active social life or babysitting her grandchildren. A retired school assistant, she is close to her 67-year-old husband and is much respected in her church for directing the music committee and the semiannual blood drive. Lorna believes in tithing (giving 10 percent of her income to charity or the church) and in the last few days has organized a church drive to raise $10,000 for earthquake relief in Haiti.

I adapted those examples from ones that Jonathan Haidt, a psychology professor at the University of Virginia, develops in his fascinating book, “The Happiness Hypothesis.” His point is that while most of us might prefer to trade places with Richard, Lorna is probably happier.

Men are no happier than women, and people in sunny areas no happier than people in chillier climates. The evidence on health is complex, but even chronic health problems (like those requiring dialysis) may have surprisingly little long-term effect on happiness, because we adjust to them. Beautiful people aren’t happier than ugly people, although cosmetic surgery does seem to leave patients feeling brighter. Whites are happier than blacks, but only very slightly. And young people are actually a bit less happy than older folks, at least up to age 65.

Lorna has a few advantages over Richard. She has less stress and is respected by her peers — factors that make us feel good. Happiness is tied to volunteering and to giving blood, and people with religious faith tend to be happier than those without. A solid marriage is linked to happiness, as is participation in social networks. And one study found that people who focus on achieving wealth and career advancement are less happy than those who focus on good works, religion or spirituality, or friends and family.

“Human beings are in some ways like bees,” Professor Haidt said. “We evolved to live in intensely social groups, and we don’t do as well when freed from hives.”

Happiness is, of course, a complex concept and difficult to measure, and John Stuart Mill had a point when he suggested: “It is better to be a human being dissatisfied than a pig satisfied; better to be Socrates dissatisfied than a fool satisfied.”

But in any case, nobility can lead to happiness. Professor Haidt notes that one thing that can make a lasting difference to your contentment is to work with others on a cause larger than yourself.

I see that all the time. I interview people who were busy but reluctantly undertook some good cause because (sigh!) it was the right thing to do. Then they found that this “sacrifice” became a huge source of fulfillment and satisfaction.

Brain scans by neuroscientists confirm that altruism carries its own rewards. A team including Dr. Jorge Moll of the National Institutes of Health found that when a research subject was encouraged to think of giving money to a charity, parts of the brain lit up that are normally associated with selfish pleasures like eating or sex.

The implication is that we are hard-wired to be altruistic. To put it another way, it’s difficult for humans to be truly selfless, for generosity feels so good.

“The most selfish thing you can do is to help other people,” says Brian Mullaney, co-founder of Smile Train, which helps tens of thousands of children each year who are born with cleft lips and cleft palates. Mr. Mullaney was a successful advertising executive, driving a Porsche and taking dates to the Four Seasons, when he felt something was missing and began volunteering for good causes. He ended up leaving the business world to help kids smile again — and all that makes him smile, too.

So at a time of vast needs, from Haiti to our own cities, here’s a nice opportunity for symbiosis: so many afflicted people, and so much benefit to us if we try to help them. Let’s remember that while charity has a mixed record helping others, it has an almost perfect record of helping ourselves. Helping others may be as primal a human pleasure as food or sex.