Giving is self-rewarding for monkeys

A new paper by Frans de Waal and Kristi Leimgruber has just been published in PNAS. This paper shows evidence that capuchin monkeys enjoy sharing with other monkeys.

Here is the official press release from Yerkes:

“ATLANTA— Researchers at the Yerkes National Primate Research Center, Emory University, have shown capuchin monkeys, just like humans, find giving to be a satisfying experience. This finding comes on the coattails of a recent imaging study in humans that documented activity in reward centers of the brain after humans gave to charity. Empathy in seeing the pleasure of another’s fortune is thought to be the impetus for sharing, a trait this study shows transcends primate species. The study is available online in the Early Edition of The Proceedings of the National Academy of Sciences.

Frans de Waal, PhD, director of the Living Links Center at the Yerkes Research Center, and Kristi Leimgruber, research specialist, led a team of researchers who exchanged tokens for food with eight adult female capuchins. Each capuchin was paired with a relative, an unrelated familiar female from her own social group or a stranger (a female from a different group). The capuchins then were given the choice of two tokens: the selfish option, which rewarded that capuchin alone with an apple slice; or the prosocial option, which rewarded both capuchins with an apple slice. The monkeys predominantly selected the prosocial token when paired with a relative or familiar individual but not when paired with a stranger.

A capuchin in this experiment selects a token.

“The fact the capuchins predominantly selected the prosocial option must mean seeing another monkey receive food is satisfying or rewarding for them,” said de Waal. “We believe prosocial behavior is empathy based. Empathy increases in both humans and animals with social closeness, and in our study, closer partners made more prosocial choices. They seem to care for the welfare of those they know,” continued de Waal.

de Waal and his research team next will attempt to determine whether giving is self-rewarding to capuchins because they can eat together or if the monkeys simply like to see the other monkey enjoying food.”

To see a video clip of the capuchins in this experiment sharing please click here.

You can also see what the press is saying by clicking a link below:

The Associated Press


Science Daily

You can download a PDF of the article here.


Nothing Boring about Studying Yawns

When it comes to contagious yawning, it seems that every new study dramatically changes our understanding of the behavior. That is not too surprising given that until recently contagious yawning did not receive much attention. Contagious yawning was a curious, almost comical, human behavior with no relevance to the rest of our or any other lives. Several years ago the thinking began to change. First, contagious yawning was linked theoretically to contagious emotions (like fear), which forms the basis for empathy. With the link to empathy, all of a sudden there was a reason to study contagious yawning in humans and other animals. Empathy is one of our defining traits with implications for our evolution and applications to mental health and the functioning of society at large. Second, experiments supported the link between contagious yawning and empathy in humans, and comparative studies showed that humans are not the only species to yawn contagiously.

A chimpanzee yawn. Photo by: William Calvin

Last week saw two new species added to the list of species capable of contagious yawning. Ramiro Joly-Mascheroni and colleagues reported in Biology Letters that dogs yawn in response to a human yawning, and Alessia Leone and colleagues reported at the 22nd Congress of the International Primatological Society that gelada baboons yawn in response to other baboons yawning. For those keeping score, five species out of five examined show contagious yawning. The totals are, in order of discovery, humans, chimpanzees, stump-tail macaques, domestic dogs, and gelada baboons. The most interesting part is that no one has yet identified a species that has not shown contagious yawning when tested. How pervasive is this trait? We have yet to find out.

A gelada baboon yawn. Photo by: Michael Nichols

Ultimately, this comparative endeavor will be very useful in assessing empathic abilities in different species. If we can find a way to experimentally link contagious yawning with empathy in nonhumans, then we will have a behavior easily identifiable that will be directly comparable across species. The ability to compare species with a single measure would be immensely helpful in understanding the evolution of empathic abilities. These studies bring us a little bit closer to resolving centuries old debates on the uniqueness of human empathy, and that is nothing to yawn about.

— Matthew Campbell

Frans de Waal and Richard Dawkins interview now available

Last November Richard Dawkins paid a visit to the Living Links Center to interview Frans de Waal for the TV special “On the Origin of Species.” You can read our original post about that visit here.

Update (2/24/09): The video seems to have been removed from youtube. Thanks to the commenters that let me know.

You can see selected clips, but not the interview with Frans de Waal, here.

I also heard a rumor that you can download the series via the UK version of iTunes. It does not seem to be available in the US version. Please let me know if someone verifies this.

— Darby Proctor

Oops! Bonobo picture by Frans de Waal graces the cover of TWO new books

In addition to being a scientist, Frans de Waal has come to be known by many people as a great photographer of the apes he studies. Frans has even released a book, My Family Album, of ape photographs that he has taken during that past 30 years.

Recently, Frans was contacted by a publishing company asking if one of his bonobo photographs could be used on the cover of a book. A few days later he received a similar e-mail. Assuming that these e-mails were from the same person Frans gave permission. However, Frans had just given permission to two separate books.

All Frans could say for himself was “I am not a photo agency, but a busy scientist, so I don’t keep very careful track of this sort of requests, of which I get too many. And so yes, in my mind I must have thought I was dealing with a single book, and never realized I gave two permissions.”

The two books, Erotomania and I Don’t: A Contrarian History of Marriage, were published just days apart.

Fortunately for Frans, no one seems too upset about the cover snaffu, although it did get some press coverage.

Update: The media followed up on their original story with an explanation of how all this happened. Read more here.

— Darby Proctor