Yawn in the presence of your pooch and they're likely to yawn right back at you, a new study shows.
The research, a series of carefully controlled experiments with 25
dogs of different breeds, confirms that dogs are more likely to "catch"
their owner's yawns than a stranger's and more likely to respond to real
yawns as opposed to fake ones. Fake yawns involve opening and closing
the mouth in the movement of a yawn without making any sound.
Researchers also strapped heart rate monitors to the dogs to make
sure they weren't yawning because they were stressed or anxious. They
"We tried to create a comfortable atmosphere in doing the experiment,
and sometimes it was so comfortable for them that they fell asleep,"
said study author Teresa Romero, a research fellow in the department of
cognitive and behavioral science at the University of Tokyo.
The study was published online on Aug. 7 in the journal PLoS One.
Although copying a yawn may not sound like such an impressive trick,
scientists think it's a sign of something important -- the ability to
empathize and bond with others.
Previous studies have shown, for example, that people who score
higher on measures of empathy are more likely to return yawns than
people who aren't as empathetic. And the ability to yawn contagiously
appears to develop with age.
"Several studies have shown that children don't begin to show
contagious yawning until around 4 years of age, and only reach adult
levels around 12 years of age," said Elainie Madsen, a comparative
psychologist at Lund University in Sweden, who has studied contagious
In the animal kingdom, contagious yawning appears to be a rare
talent. Certain apes, such as chimpanzees and bonobos, which are some of
the closest evolutionary relatives to humans, catch each other's yawns.
Beyond apes, one species of bird appears to be able to yawn
contagiously, and several recent studies have suggested that Canis familiaris, also known as man's best friend, can do it, too.
One thing researchers haven't figured out is why dogs yawn along with humans.
"There are multiple hypotheses, but the empathy hypothesis is the one
that has received most attention over the last few years," Madsen said.
"I think the evidence in support for it is accumulating."
She said that at a basic level, contagious yawning probably has
something to do with group coordination and synchronizing group
As happened in the new study, Madsen's study of contagious yawning in
puppies often lulled the dogs to sleep. She doesn't think that's an
accident. "[The dogs] internalized the emotion that yawning reflects,
and basically coordinated their behavior to that of the yawner," she
Dogs live in packs, and Madsen expects that all animals that live in
groups may demonstrate the ability to catch yawns.However, researchers
say the jury is still out on whether cats care that their owners are
"I think it would be very hard to study contagious yawning between
humans and cats," Romero said. "They don't pay very much attention to