for National Geographic News
"You scratch my back and I'll scratch yours." That sentiment has probably existed in some form or another since early humans first started walking upright and needed a hand getting down out of trees.
Cooperation enables humans and other animals to ensure their own long-term welfare and to build communities, societies, and civilizations.
Since such behavior is mutually beneficial, why is it so hard to achieve lasting cooperation? Biologists and other scientists have been intrigued by this question for years, but many studies have produced puzzling or conflicting results.
Now, one possible explanation comes from a team of scientists in Minnesota who use captive blue jays to study animal behavior. In this week's issue of the journal Science, they describe the results of a study showing that sustained cooperation depends not only on reciprocitya mutually advantageous give-and-takebut also on the timing of the benefits.
The lead author of the paper, David Stephens of the Department of Ecology, Evolution, and Behavior at the University of Minnesota in St. Paul, said the results demonstrate the importance of an effect known as temporal discounting, which refers to the tendency to devalue something over time.
"We look at delayed things as worth lesswe would rather have $100 today instead of tomorrow," he explained.
Many previous studies have shown that when animals are given a choice between a small reward now or a bigger one later, they usually prefer the immediate payoff. Even when the animals have been trained to cooperate with others for shared benefits, they are often tempted to "cheat" and act selfishly.
"We have known from work in animal psychology that non-human animals are impulsive and seem to be driven by immediate consequences," said Stephens. "They 'discount' at phenomenally high rates. The shorter the delay [of the reward], the stronger the preference for immediate gratification."
But Stephens and his colleagues found through their lab experiments that pairs of hungry blue jays were capable of sustained cooperation. It occurred most often under a combination of two specific conditions: when the birds were less concerned about an immediate reward (because the food couldn't be released for some time and gradually accumulated) and the jays' partners also showed a willingness to reciprocate.
The results suggest that "when we look at cooperation in nature, we ought to know something about the consequences and rewards organized in time related to the action," said Stephens.
As in many animal studies, the findings might hold clues to human behavior. "In human terms," said Stephens, "the kinds of conditions that promoted cooperation in jays would also be likely to promote cooperation in humans."
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