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Yawning Together
Research Blogging by Dave Munger
SeedMagazine.com
July 28, 2010
1 Everyone knows yawning is contagious. If you yawn, someone else will
probably yawn shortly thereafter. As I did the research for this column, I
noticed that nearly every article about yawning pointed out that just reading
the article itself could make you yawn. Even your dog will yawn if it sees you
yawning.
2 That last observation has been confirmed scientifically, in an elegant
experiment discussed last week by psychology graduate student Jason
Goldman. Ramiro Joly-Mascheroni, Atsushi Senju, and Alex Shepherd had an
experimenter visit dogs in their homes and yawn as the dogs looked on. In
21 of the 29 dogs tested, the dog yawned after seeing the human yawn. In a
control condition, the experimenter made a yawning motion with his mouth
but didn’t make other yawning gestures and sounds. Under these
circumstances none of the dogs yawned. The research was published in
Biology Letters.
3 Goldman points out that yawning has been observed in many species of
vertebrates, including dogs, cats, chimpanzees, and birds. But why do we
yawn? Does it serve any real purpose (besides, perhaps, subtly hinting to a
conference presenter that his or her allotted speaking time has elapsed)?
4 The biologist who blogs as “Grrlscientist” points to a pair of studies that
seem to support one explanation: Yawns help cool the brain. Andrew Gallup,
who led both studies, says the brain is more efficient when cooler, so if
yawns allow us to cool our brains, then they may allow us to think more
clearly. In one study, researchers had humans hold either cold towels or
warm towels to their foreheads: people yawned more frequently when
exposed to the warm towels. In the second study, budgerigars (parakeets)
were observed in environments of varying temperatures. When the
temperature was warmer, the budgerigars yawned more frequently,
suggesting they might be using yawns to cool off. At extremely high
temperatures, yawning again decreased, perhaps because yawns don’t help
when the temperature is too warm.
5 Gallup’s work is disputed; even the commenters on Grrlscientist’s post point
out that there are other, simpler explanations for the trends shown in the
research. For example, budgerigars may be “yawning” to cool their whole
bodies, not their brains. Humans have sweat glands for this purpose, while
birds do not, so this research wouldn’t explain human yawning. In addition,
Gallup’s research doesn’t explain why yawning seems to be contagious. If
the function of yawning is to cool my brain, why do I do it more often when I
see others yawning?