ROBERT SIEGEL, HOST:
A common complaint about the holiday season is that it's become too commercial. Selfishness and materialism are a part of human nature. At least that's what we thought. But in a recent experiment, researchers found a group of people with a very different kind of nature. NPR social science correspondent Shankar Vedantam explains what the Hadza tribe in Tanzania might have to teach us over the holidays.
SHANKAR VEDANTAM, BYLINE: If you look for items for sale on Craigslist or houses for sale in your neighborhood, you'll quickly notice something. Sellers often believe that things they want to sell are worth much more than the market is willing to pay. Psychologist Tom Wallsten at the University of Maryland sees this firsthand is his own neighborhood.
TOM WALLSTEN: There's a house across the street from us that's been on the market for months now. No doubt it would sell if they would lower the price some. So these are people who feel their house is worth more than anybody's willing to pay for it.
VEDANTAM: What we're talking about has a name in psychology. It's called the endowment effect. It's ubiquitous. Once we own something, we start to value it, we want to hold on to it. Researchers have long believed the endowment effect has biological roots. Deep in the brain, it feels worse to lose something than it feels good to gain something.
At the University of Pennsylvania, however, Coren Apicella realized that experiments into the endowment effect have usually used American college students as subjects. She decided she ought to test the phenomenon among a different group of people, a very different group.
COREN APICELLA: The Hadza are modern hunter-gatherers. They live in northern Tanzania around this mostly dried-up lake called Lake Eyasi. So because they're nomadic, they sleep outside under the stars and they move around. I have to go out and look for them.
VEDANTAM: After driving around for hours in a Land Rover, Apicella identified several groups of Hadza. Some lived closer to markets and towns and had contact with the Tanzanian economy. Others were truly nomadic; they subsisted on hunting and gathering. She gave tribe members gifts like biscuits or lighters, then she conducted a standard test of the endowment effect. She asked them if they were willing to trade their possessions.
In the United States, experiments find people are reluctant to trade. Once they get something, they don't like letting go.
APICELLA: We initially assumed that this was going to be, you know, a very easy study, clear conclusions and that this would be, you know, universal in both village Hadza, you know, the ones living in the market region, and the isolated Hadza. That both of them would show an endowment effect. That's what we assumed we would find. And, in fact, we didn't find that.
VEDANTAM: Apicella found that Hadza who had contact with the modern economy behaved exactly like American college students, but Hadza hunter-gatherers were really different. They had no trouble giving up their possessions, trading them, sharing them. They seemed invulnerable to the endowment effect. Apicella's finding challenges the idea that the endowment effect is a purely biological phenomenon. The Hadza show that it is also shaped by culture.
APICELLA: If you think about, you know, you're a hunter-gatherer, you're living a hunter-gatherer life, one possible reason why it doesn't hurt as much to give things up is that you're constantly having to give things up all the time. People are asking them for - from you, you know, demanding them from you, demanding that you share. Things come and go in hunter-gatherer life. You don't even own that much to begin with.
VEDANTAM: If you're a hunter and you kill something and don't share the food with other members of your tribe, tomorrow, your fellow members might not share their food with you. In an interdependent society, selfish acts are quickly punished. The Hadza who lived closer to a modern economy were more like us. They fell in love with their possessions because modern economies allow people room to be selfish. Capitalism even celebrates selfishness.
Apicella says back in the United States, she sometimes looks at all her stuff and thinks about the Hadza.
APICELLA: When you're on your deathbed, no one ever says, you know, I wish I had that iPhone 5S or whatever it is. You know, most people talk about their social relationships and the things that they wish they said to somebody, the things that they wish they did with somebody, and not the material possessions.
And so, I think in our society now, we're just becoming too attached to these, we're placing too much value on them. And that's part of the reason why, I think, we see the endowment effect.
VEDANTAM: Humans have spent most of their evolutionary history living in small interdependent groups. Modern economies where you can march to your own drummer are a recent development. When you think about it, this might be why the holidays are all about celebrating generosity. For a few weeks of the year, we are reminded of our ancient roots. Shankar Vedantam, NPR News. Transcript provided by NPR, Copyright NPR.