Next time you're sitting near someone who yawns, try this: Don't yawn. Odds are, you'll find that it's pretty difficult to hold back.
The reason that it's hard to stifle a yawn — especially when someone nearby is doing it and you're trying hard not to — appears to reside in the area of the brain that's responsible for motor function, a new study from England finds.
Scientists refer to the urge to yawn when you see someone else doing it as contagious yawning. This is a type of "echophenomenon." In other words, it's an automatic imitation of another person, according to the study, published online today (Aug. 31) in the journal Current Biology. Other types of echophenomena include "echolalia" (imitation of someone's words) and "echopraxia" (imitation of someone's actions. [25 Weird Things Humans Do Every Day, and Why]
Contagious yawning isn't unique to humans, either. Other animals, including dogs and chimpanzees, are also susceptible to the phenomenon, the scientists said. But the reason why yawns spread from person to person, or animal to animal, is unknown.
To study what's going on in the brain when someone "catches" a yawn, the researchers observed 36 adults who were asked to watch video clips of other people yawning. Using transcranial magnetic stimulation (TMS), the researchers measured the participants' brain activity during the experiments.
In one experiment, the people were asked to either try and stifle their yawns when viewing the yawning videos, or yawn freely. Then, the participants were asked to do the opposite. In another experiment, the participants were given the same instructions, but the researchers also applied electrical currents to the people's scalps. These currents were meant to stimulate the motor cortex, which is thought to control yawning. During the experiments, the participants were asked to estimate their urge to yawn on a sliding scale.
The researchers found that the participants were only partially successful in resisting yawning: Fewer "full yawns" were observed, but the number of "stifled yawns" increased, according to the study. And when the participants were told to resist yawning, the urge to yawn went up.
In other words, "the 'urge' to yawn is increased by trying to stop yourself" from doing so, senior study author Georgina Jackson, a professor of cognitive neuropsychology at the University of Nottingham in England, said in a statement.
The researchers also found that the propensity for "catching" a yawn was linked to the levels of brain activity in a person's motor cortex — the more activity in the area, the more inclined the person would be to yawn. Indeed, when the researchers applied electrical currents to the area, the urge to yawn increased.
The findings may have implications for certain neurological disorders, such as Tourette syndrome, that make it difficult for a person to resist certain actions, the researchers wrote in the study.
"If we can understand how alterations in cortical excitability give rise to neural disorders, we can potentially reverse them," study co-author Stephen Jackson, a professor of cognitive neuroscience, also at the University of Nottingham, said in a statement.
Originally published on Live Science.