By Zuberoa Marcos, Science Now, May 7, 2012
Yawn next to your dog, and she may do the same. Though
it seems simple, this contagious behavior is actually quite remarkable: Only a
few animals do it, and only dogs cross the species barrier. Now a new study
finds that dogs yawn even when they only hear the sound of us yawning, the
strongest evidence yet that canines may be able to empathize with us.
Besides people and dogs, contagious yawning has been
observed in gelada baboons, stump-tail macaques, and chimpanzees. Humans tend
to yawn more with friends and acquaintances, suggesting that
"catching" someone's yawn may be tied to feelings of empathy.
Similarly, some studies have found that dogs tend to yawn more after watching
familiar people yawning. But it is unclear whether the canine behavior is
linked to empathy as it is in people. One clue might be if even the mere sound
of a human yawn elicited yawning in dogs.
To that end, scientists at the University of Porto in
Portugal recruited 29 dogs, all of whom had lived for at least 6 months with
their owners. To reduce anxiety, the study was performed in familiar rooms in
the dogs' homes and in the presence of a known person but with no visual
contact with their owners.
The team, led by behavioral biologist Karine Silva,
recorded yawning sounds of the dogs' owners and an unfamiliar woman as well as
an artificial control sound consisting of a computer-reversed yawn. (To help
induce natural yawning, volunteers listened to an audio loop of prerecorded
yawns over headphones.) Each dog heard all of the sounds in two sessions, each
carried out 7 days apart. During the sessions, the researchers measured the
number of elicited yawns in dogs in response to sounds from known and unknown
people.
As the team will report in the July issue of Animal Cognition,
12 out of 29 dogs yawned during the experiment. On average, canines yawned five times more often
when they heard humans they knew yawning as opposed to control sounds.
"These results suggest that dogs have the capacity to empathize with
humans," says Silva.
That's not surprising, she says. People first began
domesticating dogs at least 15,000 years ago, and since then we've bred them to
perform increasingly complex tasks, from hunting to guiding the blind. This
close relationship may have fostered cross-species empathy over the millennia.
"This study tells us something new about the
mechanisms underlying contagious yawning in dogs," says Evan McLean, a
Ph.D. student at Duke University's Canine Cognition Center in Durham, North
Carolina, who was not part of the study. "As in humans, dogs can catch
this behavior using their ears alone." Still, he notes, the experiments
don't tell us much about the nature of empathy in dogs. "Do they think
about our emotions and internal states the way we do as humans?"
Ádám Miklósi, an ethologist at the Eötvös Loránd University in
Budapest, agrees. "Using behaviors as indicators will only show some
similarity in behavior," he says, "but it will never tell us whether
canine empathy, whatever this is, matches human empathy." Previous work
has shown, for example, that when dogs look guilty, they may not actually be
feeling guilty. "Dogs can simulate very well different forms of social interest
that could mislead people to think they are controlled by the same mental
processes," says Miklósi, "but they may not always understand the
complexity of human behavior."
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