Chimpanzees negotiate towards cooperation

Cooperation in animals is nothing new. Darwin mentioned it frequently. We know honeybees cooperate with kin to protect the colony, lions cooperate to take down a gazelle on the African savannah, chimpanzee males go on group border patrols in the African jungle, and humans often help move a disabled car off to the side of a busy highway. Cooperation, then, is quite common across the animal kingdom. New research, however, is beginning to show that, in its most complex forms, some animals may actually have more than just a simple understanding of how cooperation works.

In a study that dates back more than 70 years, chimpanzees learned to pull in a heavy box together to get the food that was placed on top of the box. More recent studies with capuchin monkeys that used a similar apparatus showed that capuchin monkeys will wait for the arrival of a partner before pulling, seemingly realizing that the drawer isn’t going to move without a friend’s help. A more recent study led by Japanese scientist Hirata used a novel task that required two chimpanzees to simultaneously pull two ends of the same rope to get food (see the picture below – a single rope is fed through a tube and two platforms, so that BOTH ends of the rope must be pulled together for the entire apparatus to move). Here too the chimpanzees learned to wait for a friend to arrive at the other end of the rope, pick it up, and pull before pulling the rope themselves. Clearly, these chimpanzees realized that they needed a partner to complete the task (i.e., obtain the food rewards).

Hirata_chimp_pull Photo from Hirata & Fuwa (2007)

A study by Melis, Hare and Tomasello looked even further into a chimpanzees’ understanding of cooperation. Chimpanzees not only learned to coordinate their pulls to pull in a platform, but learned to PICK partners that were better pullers; in other words, chimpanzees chose to “play the cooperation game” with better collaborators (in these experiments, the chimps could pull a door pin to allow one of two chimpanzees into the room with them). In this cooperation task, chimpanzees demonstrated not only that they understood they needed a partner, but seemingly that some partners were better than others.

Now there is a new study by the same team in which two of the same type of rope-pull drawers were provided to two chimpanzees (the same chimpanzees from the previous studies who already understand how the task worked). Individuals compete for unequal resources, and sometimes need to negotiate over these resources so that both parties can successfully claim a reward. This study attempted to demonstrate how such negotiations lead to cooperation.

One drawer had equal amounts of food on both ends, while the other had unequal amounts (such that one plate was full of food, while the other had even less than the other drawer). Only ONE drawer could be chosen in each trial, and thus, the chimpanzees had to decide which drawer they would pull in together. Predictably, the first individual into the testing room, the dominant chimp, chose to sit in front of the biggest plate. But often, when the subordinate chimp entered the room, he refused to sit in front of the smallest food plate, instead opting to wait patiently in front of the “equal” drawer. Such behavior demonstrates that the chimpanzees seem to have realized that by simply agreeing to the dominant chimpanzee’s initial offer, the ultimate reward would be significantly less than if they “negotiated” for an equal reward.

In many of these tests, the chimps successfully pulled in the drawer. How? Well, although sometimes the dominant chimpanzee was quite stubborn and refused to give up his large reward, often, the dominant individual realized that unless he sat in front of the “equal” drawer and pulled with the other chimpanzee, he wouldn’t get any reward at all. In this way, the chimpanzees learned to “negotiate” for cooperation. The only non-primate species to be tested in this type of cooperation task, rooks of the corvid family, succeeded in pulling in a drawer together but failed to wait for partners if released into the testing room individually. Are primates, then, the only group of animals able to understand cooperation on a more complex level? Only further research on a wide-range of species will provide an answer.

–Josh Plotnik


The Power of Mimicry

Mirror neurons, first discovered at the University of Parma in pigtail macaques, are seen as the key to a lot of interpersonal interactions ranging from imitation to empathy. These neurons erase the distinction between one’s own and somebody else’s behavior. Mirror neurons respond the same when a monkey itself is reaching for a peanut as when it sees another reach for a peanut. This is why they are also known as “monkey-see, monkey-do” neurons.

Their discovery has been hailed by Vilayanur Ramachandran: “I predict that mirror neurons will do for psychology what DNA did for biology: they will provide a unifying framework and help explain a host of mental abilities that have hitherto remained mysterious and inaccessible to experiments.”

Everyone assumes that humans have the same mirror neurons (even though until recently the evidence for this was not overwhelming), which explains why we easily adopt someone else’s facial expressions (we smile when others smile, yawn when others yawn, etc.), and why we like it when others mimic our own movements. We like to walk in stride with others and emphasize synchrony, for example, when we dance. Studies have shown that if a man or woman goes on a date with someone who mimics their movements (leans on table when we do, picks up glass when we do), we rate the date as more attractive than one who is friendly but unsynchronized with us.

Bodily synchrony is very in common animals, because many animals live in herds, flocks, or groups where it is very important to move together and be highly coordinated. The same tendency is visible in human-animal interactions. See for example the picture of the dog and Chinese soldier – this kind of synchronization would be impossible if the dog had no way of mapping its own body onto another’s – or watch the remarkable video of synchronized movement between a woman and her dog, Tina Humphrey and Chandi.

Now there is finally a study of the same love of mimicry in monkeys, following the rule that the best ideas for animal studies often come from comparisons with human behavior (something about which I blogged recently). Annika Paukner and colleagues presented brown capuchin monkeys with experimenters who either acted exactly like the monkeys or showed no such mimicry. They then measured whom the monkeys preferred to interact with. The monkeys preferred the mimicking person, which means that a) they noticed when people copied their actions, and b) they preferred such people over others, just as had been shown earlier in human studies.

The power of mimicry in social relations is going to be a major theme in future animal studies. We are working on it here at Living Links, and so are other teams, and we can be sure that neuroscience will increasingly be part of the picture.

— Frans de Waal

A lesson in formal logic

Recently, a paper published by Claudio Tennie, Josep Call and Michael Tomasello from the Leipzig Max Planck claimed to show that humans are unique because human culture “has the distinctive characteristic that it accumulates modifications over time.” They say that this is largely because, compared to the cultural learning of other animals, human cultural learning is “more oriented towards process than product.” This may very well be true. Unfortunately, there is no way to reach this conclusion based on the research described in their paper, despite what the authors would have you believe. This is because the authors rely on negative evidence as the foundation of their claim.

They compared apes to human children in their ability to learn a task (tying a loop from string in order to retrieve a reward) by watching a human model the behavior. The authors’ sketch drawing of the task is shown here:

The children were able to perform the task after watching the model; the apes were not. The authors then conclude that since no evidence had been produced to disprove their convictions, their initial claim must be correct: humans are uniquely oriented toward learning the process of solutions. In essence, the authors are making an argument of the form: the ability of apes to socially learn processes has not been proven true; therefore it is false. This is a logical fallacy, and excludes the possibility – very real in the case of negative evidence — that the test wasn’t testing what it was supposed to. For example, the children are dealing with their own species and the apes are asked to imitate another species, so the set up is inherently biased against the apes. See another blog on this website on the issue of fair comparison. Previous experiments at Yerkes Field Station have shown that chimpanzees perform better at a social learning task when another chimpanzee, instead of a human, models the task.

Another example of the problems inherent in this (faulty) logic is illustrated by the creationist website answersingenesis, which currently features the Tennie paper in its News to Note blog as evidence that, not only are we distinct from other animal species in our mechanisms of social learning, but that the very theory of evolution is itself, false. After summarizing the paper, the site observes, “If man and ape are closely related, then one might expect more adeptness in apes’ problem-solving techniques… As creationists, we know that the anatomical similarities between man and ape are the result not of a common ancestor, but of a common Creator.” It appears that using scientific papers to create a God-of-the-gaps argument is a growing trend amongst the creationist community, as an article in Nature by Johan Bolhuis and Clive Wynne received a similar response (see a reply to creationists by the authors in SEED Magazine). I do not know the personal beliefs of Tennie or his co-authors, nor do I have any interest in discussing religious beliefs here, but I have to think that even the authors can see the problem –not to mention irony- in their own logic when it is being used by a religious fundamentalist group to educate against one of science’s most stalwart theories.

-Ian Longacre