Chimpanzees' contagious yawning evidence of empathy, not just sleepiness, study shows

Apr 06, 2011
A chimpanzee

Contagious yawning is not just a marker of sleepiness or boredom. For chimpanzees, it may actually be a sign of a social connection between individuals.

New research at the Yerkes National Primate Research Center, Emory University, may help scientists understand empathy, the mechanism thought to underlie contagious yawning, in both chimpanzees and humans. The research also may help show how social biases strengthen or weaken empathy.

Scientists at Yerkes discovered chimpanzees yawn more after watching familiar chimpanzees yawn than after watching strangers yawn. The Public Library of Science One () is publishing the study online on Wednesday, April 6, 2011.

Yerkes researchers Matthew Campbell, PhD, and Frans de Waal, PhD, propose that when yawning spreads between chimpanzees, it reflects an underlying empathy between them.

"The idea is that yawns are contagious for the same reason that smiles, frowns and other are contagious," they write. "Our results support the idea that contagious yawning can be used as a measure of empathy, because the biases we observed were similar to empathy biases previously seen in humans."

Campbell is a FIRST postdoctoral fellow at Yerkes and Emory (Fellowship in Research and Science Teaching). De Waal is director of the Living Links Center at Yerkes and C.H. Candler Professor of Psychology at Emory.

They studied 23 adult chimpanzees that were housed in two separate groups. The chimpanzees viewed several nine-second video clips of other chimpanzees, in both groups, either yawning or doing something else. They yawned 50 percent more frequently in response to seeing members of their group yawn compared to seeing others yawn.

In humans, scientists have identified certain parts of the brain that are activated both when someone experiences pain and when they see someone else experiencing pain. In these experiments, people tend to show more sensitivity for members of the same social group.

The results raise the question of whether contagious yawning among humans shows the same biases: favoring members of the same social group over different social groups.

The authors note one complication: chimpanzees live in small communities where unfamiliar individuals are by definition seen as members of a separate . In contrast, humans do not necessarily see strangers as belonging to an "outgroup." For this reason, the in-group/out-group distinction may be more absolute in chimpanzees than in humans. Chimpanzees in the wild are known to be extremely hostile to external groups, which probably adds to the effects found in this study.

The authors say that contagious yawning could be a window into social and emotional connections between individuals, and suggest that insight into barriers to chimpanzee empathy may help break down those barriers for humans.

"Empathy is difficult to measure directly because it is a largely internal response: mimicking the emotional response of another. Contagious yawning allows for a measurement of empathic response that is purely behavioral, and thus can be applied more widely," Campbell writes. "Anyone who wants to increase human towards outsiders should consider that techniques to this effect could be tested out on and other animals."

Explore further: Male monkey filmed caring for dying mate (w/ Video)

More information: Campbell MW, de Waal FBM (2011) Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy. PLoS ONE 6(4): e18283. doi:10.1371/journal.pone.0018283

Related Stories

Yawning toons make an ape gape

Sep 08, 2009

Computer animations of yawning chimpanzees provoke the same irresistible grins in real chimps, according to an unusual study released Wednesday.

Chimp, bonobo study sheds light on the social brain

Apr 05, 2011

It's been a puzzle why our two closest living primate relatives, chimpanzees and bonobos, have widely different social traits, despite belonging to the same genus. Now, a comparative analysis of their brains shows neuroanatomical ...

Human-like altruism shown in chimpanzees

Jun 25, 2007

Debates about altruism are often based on the assumption that it is either unique to humans or else the human version differs from that of other animals in important ways. Thus, only humans are supposed to act on behalf of ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

Apr 18, 2014

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

CSharpner
not rated yet Apr 06, 2011
Interesting research, but I couldn't stop yawning while reading this. Just /thinking/ of yawning triggers it in me. I'm still doing it.
droid001
not rated yet Apr 06, 2011
What if chimp scratch her head? Is that mean thinking?
RobertKarlStonjek
1 / 5 (1) Apr 07, 2011
Fess up readers ~ you yawned too, didn't you...

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.