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Chimpanzees Play the Ultimatum Game

The Ultimatum Game is the gold standard of the human sense of fairness. People have played it all over the world, but until now nonhuman animals have never successfully engaged in this game. One individual needs to propose a reward division to another that the other needs to accept before both can obtain the rewards. Obviously, this procedure is not easily arranged without language.

Researchers at the Yerkes National Primate Research Center, Emory University, in collaboration with colleagues from Georgia State University, are the first to obtain positive results with chimpanzees. They have shown that our closest relatives possess a sense of fairness that has previously been claimed to be uniquely human. The findings are now available in an early online edition of the Proceedings of the National Academy of Sciences (PNAS), suggesting a long evolutionary history of the human aversion to inequity. Possibly, the common ancestor of apes and humans shared a similar preference for fair outcomes.

See chimpanzees play the ultimatum game here!

The Yerkes team wanted to determine how sensitive chimpanzees are to the reward distribution between two individuals if both need to agree on the outcome. According to first author Darby Proctor, PhD, “We used the Ultimatum Game because it is the ultimate test of the human sense of fairness given both partners must agree on a distribution for either to receive rewards.” Humans typically offer generous portions (such as 50%) of the reward to their partners, and that’s exactly what Proctor and her team recorded in their study with chimpanzees.

Co-author Frans de Waal, PhD, adds, “Until our study, the behavioral economics community assumed the Ultimatum Game could not be played with animals or that animals would choose only the most selfish option while playing. We’ve concluded that chimpanzees not only get very close to the human sense of fairness, but that they may actually have exactly the same preferences as our own species.” For purposes of direct comparison, the study was also conducted separately with human children.

In the study, researchers tested six adult chimpanzees (Pan troglodytes) and 20 human children (ages 2 – 7 years) on a modified Ultimatum Game. One individual chose between two differently colored tokens that, with his or her partner’s cooperation, could be exchanged for rewards (small food rewards for chimpanzees and stickers for children). One token offered equal rewards to both players, whereas the other token favored the individual making the choice at the expense of his or her partner. The chooser then needed to hand the token to the partner, who needed to exchange it with the experimenter for food. This way, both individuals needed to be in agreement.

Both the chimpanzees and the children responded like adult humans typically do. If the partner’s cooperation was required, the chimpanzees/children split the rewards equally. However, with a passive partner, who had no chance to reject the offer, they went for the selfish option.

Chimpanzees, who are highly cooperative in the wild, likely need to be sensitive to reward distributions in order to reap the benefits of cooperation. Thus, this study opens the door for further explorations into the mechanisms behind this human-like behavior.

Talk to the Hand: New Insights into the Evolution of Language and Gesture

The APS Observer has a nice piece about Amy Pollick‘s work. Dr. Pollick is a graduate of the Living Links Center.

You can see the original version here, or read below.

-Darby Proctor

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Frans de Waal Interview with the MDM Wonderlace

You can read the full text of the interview here.

Frans de Waal featured on ABC news

Frans de Waal discusses morality and chimpanzee behavior on ABC news.

Click here for the video.

-Darby Proctor

New climbing structure for chimps!

We just renovated one of our chimpanzee habitats. You can see pictures of the chimps enjoying their new climbing structure below.

The chimps were very excited about the new structure. We had a lab pool going to try and guess who would touch it first. Matt won by picking Tai! Kudos Matt. Other chimps soon followed, and they seem to be enjoying their new play space.


The new climbing structure.

Tai climbing the ladder. She was the first chimp to get on the new climber!

Steward (the alpha male) enjoying some apples on the climber.

–Darby Proctor

Frans de Waal on the human primate: Make love, not war

This was originally posted on Scientific American. See the original here.

Editor’s Note: This post is the last in a four-part series of essays for Scientific American by primatologist Frans de Waal on human nature, based on his ongoing research. (The first post, on our sense of fairness, can be read here; a second post, on the impact of crowding, is here; and a third post on power and coalitions is here.) De Waal and other researchers appear in a series of Department of Expansion videos focusing on the same topic.

The origin of human aggression and warfare remains hotly debated. Until now, this debate has been dominated by what chimpanzees do and how this compares with our own species. It is little known, however, that we have an exactly equally close primate relative, the bonobo. This species makes Hobbesians very uncomfortable, so they do everything to marginalize it. One anthropologist seriously suggested that we should ignore bonobos, because they are close to extinction, not realizing that by the same token we should also ignore “Lucy,” “Ardi” and all those other ancestors that bit the dust. Others treat bonobos as a wonderful afterthought, a great curiosity, but irrelevant to where we come from.

The first study to compare bonobos and chimpanzees was carried out at the Hellabrunn Zoo in Munich. German scientists made a list of differences between both species, including the bonobo’s sensitivity, peacefulness and obvious sex drive. If these differences were already known in the 1950s, one might ask: Why was the bonobo absent from the debates on human aggression, and still is? Well, that study was published in German, and the time that English-speaking scientists read anything other than English is long past. Another reason is cultural: Victorian attitudes prevent most American or British scientists from touching the bonobo’s eroticism. In the 1990s a British camera crew traveled to the remote jungles of Africa to film bonobos only to stop their cameras each time an “embarrassing” scene appeared in the viewfinder. And National Geographic never published the explicit bonobo pictures brought home by one of its photographers (which were subsequently put to good use by this photographer, Frans Lanting, and myself in Bonobo: The Forgotten Ape).

But far more important is the fact that bonobos fail to fit established notions about human nature. Believe me, if studies had found that they massacre one another, everyone would know about bonobos. Their peacefulness is the real problem. I sometimes try to imagine what would have happened if we’d known the bonobo first and the chimpanzee only later—or not at all. The discussion about human evolution might not revolve as much around violence, warfare and male dominance, but rather around sexuality, empathy, caring and cooperation. What a different intellectual landscape we would occupy!

Bonobos act as if they have never heard of the killer ape theory that remains popular in anthropological circles. Among wild bonobos there’s no deadly warfare, no male dominance, and enormous amounts of sex. They make love, not war. Science had more trouble with them than a 1960s family had with its long-haired, pot-smoking black sheep who wanted to move back in. They turned off the lights, hid under the table and hoped that the uninvited guest would go away.

ABOUT THE AUTHOR

Frans de Waal, PhD, is a Dutch-American primatologist known for his popular books, such as Chimpanzee Politics: Power and Sex among Apes (1982) and The Age of Empathy: Nature’s Lessons for a Kinder Society (2009). He teaches at Emory University in Atlanta where he directs the Living Links Center at the Yerkes National Primate Research Center. He has been elected to the National Academy of Sciences and the Royal Netherlands Academy of Arts and Sciences.

Frans de Waal on the human primate: Strength is weakness

This was originally posted on Scientific America. You can see the original here.

Editor’s Note: This post is the third in a four-part series of essays for Scientific American by primatologist Frans de Waal on human nature, based on his ongoing research. (The first post, on our sense of fairness, can be read here, and a second post, on the impact of crowding, is here.) De Waal and other researchers appear in a series of Department of Expansion videos focusing on the same topic.

Chimpanzees continually play coalition games; power is rarely in the hands of a single individual. The male with the most supporters usually wins, which is why size and strength are such poor predictors of the hierarchy. Diplomacy Is at least as important, as explained in Chimpanzee Politics (1982).

Once, in a large zoo colony an old male faced a choice between either attaching himself to the most powerful player, the reigning alpha male, and deriving a few benefits in return, or helping a young-and-coming male challenge the alpha. The old male took the second route. The result was a new leader who owed his position to the old male, and as a result the latter gained far more leverage than would have been possible under the reigning alpha male. Throwing his weight behind the young male was consistent with the “strength is weakness” paradox known in international politics and coalition games played with humans. The most powerful player is often the least attractive political ally.

Ever since Thucydides wrote about the Peloponnesian War, it has been known that nations seek allies against nations perceived as a common threat. Fear and resentment drive weaker parties into one another’s arms, making them weigh in on the lighter side of the balance. The result is a power balance in which all nations hold influential positions. Sometimes a single country is the main “balancer,” such as Great Britain was in Europe before World War I.

Balance of power theory remains heavily debated in international affairs, and I would argue that it also applies to primate coalitions. This means that no player can take its position for granted, because even the most powerful player—or precisely the most powerful—faces forces that seek to erode its power.

Balancing tendencies are reflected in our everyday psychological reactions, such as rooting for the underdog during a sports match or feeling schadenfreude over the mishaps of successful and powerful people. We don’t take any pleasure in the misfortune of the poor, but look at our fascination with political scandals and celebrities embarrassing themselves or going to jail. We’re continually ready to bring down those who rise to positions above ours, thus demonstrating our equalizing tendencies.

ABOUT THE AUTHOR

Frans de Waal, PhD, is a Dutch-American primatologist known for his popular books, such as Chimpanzee Politics: Power and Sex among Apes (1982) and The Age of Empathy: Nature’s Lessons for a Kinder Society (2009). He teaches at Emory University in Atlanta where he directs the Living Links Center at the Yerkes National Primate Research Center. He has been elected to the National Academy of Sciences and the Royal Netherlands Academy of Arts and Sciences.

Frans de Waal on the human primate: Is it “behavioral sink” or resource distribution?

Previously posted on Scientific American. See the original here.

Editor’s Note: This post is the second in a four-part series of essays for Scientific American by primatologist Frans de Waal on human nature, based on his ongoing research. (The first post, on our sense of fairness, can be read here.) De Waal and other researchers appear in a series of Department of Expansion videos focusing on the same topic.

In the 1960s Jack Calhoun placed an expanding rat population in a crammed room and observed how the animals killed, sexually assaulted and, eventually, cannibalized one another. The magnetism of the crowd and the behavioral deviancy led Calhoun to coin the phrase “behavioral sink.”

In no time popularizers were comparing politically motivated street riots with rat packs, inner cities to behavioral sinks, and urban areas to zoos. Warning that society was heading for either anarchy or dictatorship, Robert Ardrey, a popular science journalist and author of African Genesis, remarked in 1970 on the voluntary nature of human crowding and its ill effects. These views entered mainstream thinking: The negative impact of crowding became a central tenet of the voluminous literature on aggression.

In extrapolating from rodents to people, however, these writers were making a giant leap. Compare, for instance, the per capita murder rates with the number of people per square kilometer in different nations. If things were straightforward the two ought to vary in tandem, but there is in fact no statistically meaningful relation. Among free-market nations the U.S. is an anomaly by having the highest homicide rate despite a low population density. Some seek the explanation in U.S. gun laws, but this issue remains largely taboo.

To see how other primates respond to being packed together, we compared rhesus monkeys in crowded cages with those roaming free on Morgan Island in South Carolina. We also compared chimpanzees in indoor enclosures with those living on large forested islands. Nothing like the expected crowding effects could be found. If anything, primates become more sociable in captivity, grooming each other more—probably in an effort to counter the potential of conflict, which is greater the closer they live together. Primates are excellent at conflict resolution.

For the future of the world this means that crowding by itself is perhaps not the problem it is made it out to be. Resource distribution seems the real issue. This was already true for Calhoun’s rats, the violence among them could be explained by concentrated food sources and competition. Also for humans, I would worry more about sustainability and resource distribution than population density.

For more on this topic, see: Coping with Crowding by Frans de Waal, Filippo Aureli and Peter Judge; May 2000; Scientific American.

ABOUT THE AUTHOR

Frans de Waal, PhD, is a Dutch-American primatologist known for his popular books, such as Chimpanzee Politics: Power and Sex among Apes (1982) and The Age of Empathy: Nature’s Lessons for a Kinder Society (2009). He teaches at Emory University in Atlanta where he directs the Living Links Center at the Yerkes National Primate Research Center. He has been elected to the National Academy of Sciences and the Royal Netherlands Academy of Arts and Sciences.

http://www.scientificamerican.com/blog/post.cfm?id=frans-de-waal-on-the-human-primate-2010-07-21

Frans de Waal on the human primate: Fair is fair

Previously posted at Scientific American. See the original here.

How often do we see rich people march in the street shouting that they’re earning too much? Or stockbrokers complaining about the “onus of the bonus”? Protesters typically are blue-collar workers yelling that their jobs shouldn’t go overseas or that they should earn more. A more exotic example was the 2008 march through the capital of Swaziland by poor women who felt that the king’s wives had overstepped their privileges by chartering an airplane for a shopping spree in Europe.

Fairness is viewed differently by the haves and have-nots. The underlying emotions and desires aren’t half as lofty as the ideal itself. The most recognizable emotion is resentment. Look at how children react to the slightest discrepancy in the size of their pizza slice compared with their siblings’. They shout, “That’s not fair!” but never in a way transcending their own desires.

An experiment with capuchin monkeys by Sarah Brosnan, of Georgia State University’s CEBUS Lab, and myself illuminated this emotional basis. These monkeys will happily perform a task for cucumber slices until they see others getting grapes, which taste so much better. They become agitated, throw down their measly cucumbers, and go on strike. A perfectly fine vegetable has become unpalatable! Not all economists, philosophers and anthropologists were happy with our interpretation, because they traditionally consider the “sense of fairness” uniquely human. But by now there are many other experiments, even on dogs, that confirm our initial findings.

Obviously, things get extremely political if one claims that a desire for income equality has evolutionary backing, but it is hard to deny that the collapse of the world economy in 2008 was partly due to a massive misjudgment of human nature. We’re considerably less selfish and more social than advertised.

ABOUT THE AUTHOR

Frans de Waal, PhD, is a Dutch-American primatologist known for his popular books, such as Chimpanzee Politics: Power and Sex among Apes (1982) and The Age of Empathy: Nature’s Lessons for a Kinder Society (2009). He teaches at Emory University in Atlanta where he directs the Living Links Center at the Yerkes National Primate Research Center. He has been elected to the National Academy of Sciences and the Royal Netherlands Academy of Arts and Sciences.

The views expressed are those of the author and are not necessarily those of Scientific American.

Prestige Affects Cultural Learning in Chimpanzees

A new study by the members of the Living Links Center has just come out in PLoS ONE. You can read the study here, or take a look at the press release below.

– Darby Proctor

 

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