Human cooperation often comes down to one key understanding: You help me, I’ll help you. Social animals, including dogs, also help others, even nonrelatives. But many scientists assume that animal cooperation is a different breed. They see animals as less likely to have the cognitive power to remember a favor and then return it, especially when favors exchanged are not identical.
“The difficulty with reciprocal cooperation is that there is a time delay,” says behavioral ecologist Michael Taborsky of the University of Bern in Switzerland. “You need to predict at the moment that you help someone else that this will increase the chances that you get help in the future.”
Now, using a group of Belgian shepherds belonging to the Swiss military, Taborsky and his then-graduate student Nastassja Gfrerer have shown that dogs do in fact repay help, even when the delivery methods for the reward differ. The findings, reported in Biology Letters, hint at an evolutionary root for reciprocal cooperation in animals, including humans.
The team began by teaching about a dozen Belgian shepherds to help each other access food using two different methods. In one setup, a dog pulled a rope to draw a wooden platform topped with food to another dog in a neighboring kennel. In another, the dog pushed a lever to open a box containing food for the neighbor. The helping dog didn’t receive food.
The researchers then tested whether a dog would return the food favor using the rope, even to a partner that originally delivered help using the lever, or vice versa. About 10 dogs experienced four different partner types spread over a week—a cooperator who pulled a rope, a cooperator who pushed a lever, a “defector” who didn’t pull the rope, and a defector who didn’t push the lever. (The defectors hadn’t been taught how to help.)
The day after each of these interactions, the researchers again paired each dog with the same partner and gave them the opportunity to return the favor using the alternative mechanism. They also conducted a separate trial on each of these days pairing each dog with an empty kennel to account for any intrinsic desires for pushing or pulling.
The team found that dogs rarely helped partners who had refused to help them. In fact, there was no statistical difference between the number of pulls or pushes dogs made for these defectors compared to those made for an empty kennel. But dogs nearly always helped those who had previously helped them.
“This was actually quite surprising,” says Taborsky. “It means that they do not just copy some behavior that they have experienced before. They generalize the receipt of help from someone and transfer that into a completely different task by which they can return the received help to that particular individual.” While previous primate studies suggest that similar dynamics may occur in the wild, Taborsky says his is the first to document this behavior in a controlled setting.
Anthropologist Michael Gurven of the University of California, Santa Barbara, wonders whether the researchers would have found the same result if the dogs’ actual rewards differed. “The specific task is different but the ends are still the same,” he says. “It was still food.” Humans often reciprocate across different currencies. In his own research exploring cooperation in a group of Bolivian horticulturalists, he observed community members repaying one food type with another, or with services like babysitting or caring for a sick neighbor.
Indeed, Taborsky and his then-graduate student Manon Schweinfurth have recently shown that Norway rats can also cooperate in this fashion, providing food at one time point and being rewarded with grooming help at another. Taborsky is considering the design of a similar study in dogs. He suspects that other animal species are also capable of reciprocal cooperation using different tasks or currencies, but more controlled experiments are needed.
“We have been showing in rats and in dogs that these animals work by the same or similar principles as humans do,” Taborsky says, “which means that the high propensity to reciprocal help in humans is not a cultural phenomenon but an evolved response.”
Gurven agrees that the findings suggest that reciprocal cooperation might be more widespread than scientists thought. “Another example,” he says, “of chipping away at human uniqueness.”