All For One? Why Humans Cooperate

Feb. 16, 2005 — -- Despite the fact that humans sometimes fight fiercely among themselves, one of our most distinctive human traits is our willingness to cooperate with others. Why we are like that is one of the really big questions confronting evolutionary psychologists.

"The fact that people cooperate is quite mysterious," says Robert Kurzban, an assistant professor of psychology at the University of Pennsylvania. "People are constantly talking about how organisms are competing, but one thing that humans do that's distinctive is they cooperate in groups."

Other animals, from ants to wolves, also cooperate to a degree, but not as extensively as humans. As evolutionary psychologists, Kurzban and Daniel Houser of George Mason University are trying to figure out why.

Since most people are trying to get ahead in life, it would seem that we are primarily competitors, not cooperators, and while the "big question is still out there," as Kurzban puts it, competition may be a key factor in why we cooperate.

"If I had to make a guess I think it's at least possible that one of the important features behind human cooperative behavior is actually intergroup competition," Kurzban says. "You can't compete in groups unless people are cooperating within groups."

Language Promotes Teamwork

Just ask any coach. If a team doesn't play as a team, it will likely lose, regardless of the talents of individuals within the team.

There's more than a little irony in that because if the individual members of the team are extremely competitive, they'll still lose. So somehow they have to learn to cooperate with each other.

The evolution of that peculiar trait probably contributed to the development of many other human abilities, including the capacity to discuss our needs and our mutual goals.

"If you think about language, what language allows us to do is coordinate our behaviors in ways that other organisms just can't," Kurzban says. "You go over there and stand behind that tree, and I'll come over here and throw this rock, or whatever.

"The fact that people can coordinate in large groups means they can cooperate with one another."

To try to understand how that works, Kurzban and Houser recruited 80 college students, divided them into groups, and gave each participant 50 tokens. The students were told they could keep all of the tokens, or put some of them in a pot that would double in value and then be distributed equally among all the members of the group.

The idea of the experiment was to find out how many of the participants were "cooperators," and would share some of their wealth for the good of the community, and how many were "reciprocators," who would wait and see how much others contributed before deciding how much to toss into the communal pot, and how many were "free riders." We all recognize those characters. Not a single bloody token for the common good.

Most Wait to Receive Before Giving

Now here's the first surprise, perhaps. Most of us aren't cooperators. We're reciprocators by a whopping margin. No matter which participants were assigned to which groups, about 63 percent always waited to see what George was willing to contribute before anteing up themselves. About 20 percent were free riders, refusing to contribute anything at all and about 17 percent were classified as cooperators who were willing to chip in regardless of what anyone else did.

Continuing this level of surprise, the researchers think that cooperators, although in the minority, constituted the most powerful force within the group. They established the level of contribution, and the reciprocators, not willing to be left behind, coughed up an equal amount, maintaining the status quo and enlarging the pot that was to be shared by all.

Kuzban and Houser, who published their findings in a recent online edition of the Proceedings of the National Academy of Sciences, think there's something here that could be useful beyond the college lab. How a team leader communicates with all the members of the team can be a major factor in the success of the team.

Since reciprocators respond to cooperators, they need to know quite clearly that George contributed a bundle or they won't give much themselves. Of course, the free riders won't give a rip.

So let's hear it for the cooperators.

"These cooperators are doing an interesting amount of work because when they are placed in groups with reciprocators they are essentially enlisting large amounts of cooperation from the reciprocal types. So these guys are a key element. They draw out the reciprocators," Kurzban says.

"They plant seeds of cooperation."

Of course, we're not all college students, and that can be a very different animal. "It's what we call a convenience sample," as Kurzban puts it.

But he believes these findings will be replicated in other experiments involving different age groups and different cultures, including Japan.

Other researchers have completed similar studies, and "they find substantial stability among the different age groups," Kurzban says. "That gives me some optimism."

In the end, he hopes to answer the "big question." It will likely show that cooperation evolved in humans because those cultures that didn't cooperate, regardless of how large or how small they were, didn't survive.

In human evolution, survival of the fittest may simply mean we learn to work together or we die.

Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.