Science Watch

Like many people, Richard Schuster, PhD, would rather go out to dinner with a friend than by himself. It's simply more pleasurable, says the University of Haifa psychology professor. Likewise, people enjoy the feeling of cooperating with others, whether by dancing together, singing in a group, or working together to solve a problem.

Now, Schuster and his colleagues are trying to prove a more controversial claim: Animals also enjoy cooperating, and they'll work together even when cooperating goes against their short-term material interests.

Animals up and down the evolutionary scale cooperate—from ants to bees to lions to chimpanzees—and psychologists and biologists have long been interested in unraveling the mystery of why one animal would help another when, evolutionarily speaking, there's no reason to help any creature that doesn't share your genes.

Schuster's idea that animals enjoy cooperating, he says, runs counter to a body of research that sees animal cooperation as motivated only by self-interest.

"Most of the interest in cooperation has been what you get for it," Schuster says. He and his colleagues are trying to change that by plotting out in minute detail the behaviors of rats and dolphins as the animals work together with others of their species. They aim to prove, in essence, that for many animals being in the company of others can be intrinsically rewarding.

Doing so, they believe, could help explain where humans' inclination to cooperate arose.

Rodent exercise partners

Many forms of animal cooperation benefit all the individuals involved. Fish, for example, nibble dead skin and parasites off other fish, keeping one set healthier while feeding the other.

But research by Schuster shows that some animals will choose to cooperate even when no one immediately benefits. In a 2004 study, published in Behavioral Processes (Vol. 66, No. 3), he and then-graduate student Amir Perelberg, PhD, now a postdoctoral researcher at Hebrew University of Jerusalem, placed rats in a maze where they could choose to enter one of two chambers. In the first, the rats earned a reward of saccharine-sweetened water by running back and forth from one end of the chamber to the other, stopping for at least half a second on each side. In the second, they got the same reward by coordinating back and forth running with a partner—stopping together for at least half a second on each side.

Despite the fact that the cooperation task was more difficult to learn than running alone—the rats had to coordinate their behaviors, so they succeeded less often—and the reward was the same, the rats chose by nearly a three-to-one margin to run together rather than alone. The rats that were better at coordinating their running and performed the task correctly more often more strongly preferred to run together.

Those findings might seem surprising, but they make some evolutionary sense, says Perelberg—particularly in social species such as dolphins, lions, chimpanzees and, yes, even rats.

"We cooperate because we enjoy doing it. But what we really do is strengthen our social relationships, so later on we can use these relationships to gain some other benefits," Perelberg says.

Researchers observing bottlenose dolphins, for example, have found that adolescent males form sophisticated alliances and coalitions with no apparent immediate benefits. But 10 years later, those dolphins use the same alliances to work together to herd and guard females for mating.

Taking their work from the lab to the field, Perelberg and Schuster have conducted a series of studies at a "swim with dolphins" tourist attraction where the dolphins interact with humans but are free to swim into the open ocean as well.

Perelberg spent eight months observing the 13 dolphins in the enclosure for hours each day. In one study, in press in the Journal of Comparative Psychology, he looked at how dolphins approached the human guides who worked at the site to receive petting.

Dolphins, which engage in social rubbing with one another, also like to be petted by familiar humans. But Perelberg found that the dolphins tended to approach humans in pairs, even though it cut down on the total amount of petting each received. Also, the animals approached in pairs that made social-bonding sense—the ones that might provide a survival advantage later. Most often it was mothers and calves, or pairs of adolescent males, that approached together.

In another study, published in the Journal of Comparative Psychology (Vol. 122, No. 2), Perelberg found that those same pairs were most likely to coordinate their breathing—a marker for coordinating other, less visible behaviors.

Selfish blue jays?

Richard Schuster says that his work is a reaction to decades of animal cooperation research that has ignored the social aspects of cooperation. That work, in which animals are placed in separate boxes and don't interact during an experiment, has found that it's difficult to induce animals to give up an immediate reward in order to cooperate, except under special conditions.

In one 2002 study published in Science (Vol. 298, No. 5601), for example, David Stephens, PhD, an evolutionary ecologist at the University of Minnesota, found that blue jays, placed in separate boxes, wouldn't initially cooperate in a prisoner's dilemma-style game. But when one blue jay was forced to cooperate for many trials, the other blue jay eventually began to cooperate, too.

Stephens says that he agrees with Schuster on two essential points:

"I don't doubt that animals are sensitive to social situations," he says, "and there's no doubt that some of the economic consequences of cooperation are quite long-term—I don't see the time scale of the benefits as being an issue."

Where Schuster and Stephens part ways, though, is on the mechanisms that underpin cooperation. Schuster believes that cooperation creates a "positive affective state" in animals. In other words, they enjoy it.

Lee Dugatkin, a University of Louisville biologist and expert on animal cooperation, also says he isn't sure that Schuster's dolphin studies provide proof that animals gain an emotional reward by cooperating.

"I'm not convinced that there aren't some more immediate benefits that these animals are getting by being together," he says.

From lab to field

Meanwhile, Schuster and his colleagues are working in the field and lab to accumulate more evidence that animals do "feel nice" about working together.

In the lab, one graduate student is testing whether rats will still prefer to run together rather than alone when they can earn a better reward for running alone. And preliminary results suggest that they still prefer to run together, even when they have to give up a better reward to do so, Schuster says.

In the field, Schuster traveled to Botswana this fall to study how lions hunt cooperatively. A study published in Nature (Vol. 449, No. 7,165) found that lions hunt more efficiently alone: Hunting together reduces their food intake by up to 90 percent. The paper, written by ecologists, suggests that by living in groups, both predator and prey help stabilize the food chain, and that if lions hunted alone the imbalance could tip both species toward extinction.

But Schuster believes that something more is at work.

"Why would the lions hunt together if it does not immediately pay off?" he asks. "I agree that the answer to the 'why' question is partly biological—there has to be some kind of future benefit from cooperating. But this future benefit is not a sufficient explanation for why an individual would cooperate, because animals also need immediate gratification. Our work shows evidence for evolution having designed them to experience pleasure from cooperating with others."

And if that's true for animals, then perhaps it's true for humans as well, he posits—evolution has prodded us toward enjoying one another's company, and toward cooperating: "Social behavior is its own reward. And that's a really important message for psychology," Schuster says.


Lea Winerman is a writer in Washington, D.C.