Yawning is contagious for most humans and some animals. But what's behind it? (Image credit: bymuratdeniz via Getty Images)
Watching or hearing someone yawn can make you yawn too. This phenomenon is not limited to humans; some animals can also succumb to the contagiousness of yawning.
But why is yawning so easily contagious?
Brain cells known as mirror neurons may be involved in this effect, Dr. Charles Sweet, a board-certified psychiatrist and clinical advisor for Linear Health, told Live Science. Mirror neurons fire in response to actions we observe in others.
“When you see someone yawn, these neurons fire,” Sweet explained. This neurological mechanism may explain why yawning spreads so quickly among social groups.
Research has also shown that people and animals are more likely to yawn in response to the yawns of familiar people than to the yawns of strangers. For example, in a 2013 study, dogs yawned more often when they saw their owner yawn than when they saw a stranger yawn. This pattern, known as “familiarity bias,” is likely due to attentional bias, said Andrew Gallup, a professor of behavioral biology at Johns Hopkins University, since people naturally pay more attention to those in their social circle.
One theory is that contagious yawning may have evolved to enhance the ability to detect threats in groups, Gallup told Live Science in an email.
In a 2007 study published in the journal Evolutionary Psychology, Gallup and his colleagues found that yawning helps cool the brain. This cooling effect may increase the yawner’s alertness and mental processing efficiency, Gallup suggested. If yawning spreads through a group, it may help increase the group’s awareness of potential threats, the team suggested.
Later Gallup studies on humans showed that simply observing others yawn can improve a person's ability to detect threats, further supporting the theory that contagious yawning promotes increased levels of vigilance in a group.
Another hypothesis suggests that contagious yawning evolved to synchronize groups. Yawning follows a natural circadian rhythm and often signals transitions between activities. Therefore, when yawning spreads within a group, it may serve to align activity patterns and behavior, Gallup explained.
Support for this hypothesis comes from a recent study of wild African lions (Panthera leo). The researchers observed the yawns of 19 lions in two social groups and analyzed the relationship between yawn contagion and motor synchrony—when individuals show the same changes in behavior. The results were striking: Lions that “caught” a yawn from another lion were 11 times more likely to mimic the movements of the lion that yawned first, compared to lions that did not catch the yawn.
Not everyone is equally susceptible to contagious yawning. In controlled studies, between 40% and 60% of normal volunteers yawned in response to watching a video of another person yawning.
A key question in the research is whether contagious yawning is linked to empathy. Several studies have been conducted, but the results have been mixed. “Some studies have found suggestive links, while others have failed to confirm such a link,” Gallup explained.
While early research suggested that children with autism were less likely to yawn contagiously than children without autism, a later study found that when participants were explicitly asked to focus on yawning, the difference disappeared, Gallup said, emphasizing that attention also plays an important role in whether yawning is contagious.
One of the most consistent findings is the negative association between contagious yawning and psychopathy. “People who score high on psychopathic traits tend to be less susceptible to contagious yawning,” Gallup noted. (Psychopathic Traits
Sourse: www.livescience.com
