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Study after study bears him out. In one of De Waal's experiments at Atlanta's Yerkes Regional Primate Research Center, for example, pairs of capuchin monkeys (the species favored by organ grinders) have to cooperate in dragging a heavy tray so they can get the food on it. They quickly figure out how to do so, sharing the effort and the food. But when the food is placed on one side of the tray, giving only one monkey access to it, they still share. "There is no need for the one who gets all the food to do it," says De Waal. "He could sit in the corner and eat all by himself."
In another experiment, De Waal and his students reward two monkeys for a task by giving them cucumber. It's not a favorite food, but they happily go on doing the task anyway. Then the scientists begin giving one of the monkeys grapes--like caviar for a capuchin. At that point, the monkey that is still getting cucumber refuses to play. Says De Waal: "It's like me discovering my colleague, who works just as hard as I do, gets a salary that is twice the size of mine. I was perfectly happy before."
Both those results can be explained in part by self-interest. But De Waal has also observed behavior that can be seen only as empathetic. When a male loses a fight and sits on the floor screaming, the other chimps will comfort it. "They come over to these distressed individuals and embrace them and kiss them and groom them, and try to calm them down," De Waal says. True, there's an implied benefit for the comforters--the hope that others will do the same for them if they end up in that situation--but that's a level of emotional abstraction that would once have been presumed impossible.
At TerraMar Research on Bainbridge Island, Wash., animal behaviorist Toni Frohoff has also observed dolphins behaving with what appears to be altruism--although not predictably. In one case, she recalls, she and her colleagues watched a group of dolphins assemble around a female swimmer the researchers later learned was exhausted to the point at which she was afraid for her life. "Conversely," Frohoff says, "I have been 'abandoned' [by dolphins], where all of a sudden they'd disappear and I'd see a shark."
Does that mean the supposed altruism of dolphins--not just in Frohoff's studies but also in anecdotal reports of the animals' rescuing sailors--is a myth? No, she says: "The mythology in some cases is true." But dolphins have adapted so long in such a different environment to humans that there's reason to suppose that their ethics might be equally different to ours.
Dolphins, dogs and primates are the usual suspects when scientists talk about higher mental functions, but fairness, at least, extends even deeper into the lower animal kingdom. If you watch rats wrestle, says Stephen Siviy, a psychologist at Gettysburg College, you'll see that the bigger rat lets the smaller rat win every now and then so that the smaller rat will keep playing. That, he says, could be interpreted as a sense of fair play, although he emphasizes that a rat's behavior is probably Darwinian--based not on thoughtful consideration but on what has worked in the past to keep species alive. "I can't see a rat sitting around and contemplating the ethical consequences of what it's doing," he says.