In This Corner
Mission to Limatambo
Students and faculty from Tufts Dental School brought their skills to an orphanage in the mountains outside of Cuzco, Peru
More than half of study subjects were found to yawn within five minutes of seeing another person yawn. Photo: iStockphoto
Ask The Professor
Why do people yawn? Is it contagious?
This month’s faculty expert, Brian Cohen, director of the Pratt Diagnostic Center at the Tufts Medical Center and assistant professor of medicine, answers:
Yawning is the universal sign of boredom, but why do we do it? No one seems to really know. It is an involuntary act in which we open our mouth and take a deep breath, yet the theory that we do it to get more oxygen or get rid of more carbon dioxide does not appear to be correct. Researchers gave college students gases with different mixtures of oxygen and carbon dioxide to breathe, and the frequency and duration of yawns did not change.
It does, though, seem to correlate with boredom. In one study, a color test pattern provoked more yawns than a music video. And it has been documented in utero, perhaps further confirming the boredom theory.
But this does not appear to be the whole story. There are some clues as to the parts of the brain involved. For instance, injecting certain neurotransmitters into a part of the brain called the hypothalamus induces yawning. Yawning is a routinely observed feature of heroin withdrawal. And Olympic athletes have been noted to yawn frequently before their events.
Yawning does appear to be contagious. More than half of study subjects were found to yawn within five minutes of seeing another person yawn. Blind people have been noted to yawn after hearing a tape of someone yawning. This observed contagion starts in the first years of life.
Contagious yawning has also been documented in chimpanzees, and dogs have been noted to yawn in response to a yawning human, but mere mouth movements by control subjects did not elicit a yawn. One theory of contagious yawning is that it is an expression of empathy. Indeed, dogs have been shown in other experiments to be attuned to humans’ mental states.
