Next time you catch yourself yawning, look around: Did anyone close to you let out his or her own sleepy "ahhh"? Turns out, close friends and family are more likely than acquaintances or strangers to catch someone's yawns, a new study finds.
The researchers suggest this yawning contagion is, in part, the result of empathy, in which we can attempt to see things from another person's angle and respond to that person's emotions.
"I think what the study does is it supports the idea that empathy is the mechanism that underlies contagious yawns," said Matthew Campbell of Emory University, who wasn't involved in the study. "The idea is that it's the same mechanism by which we catch smiles or frowns or fearful expressions."
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While yawns would not seem to have a connection with any particular emotion (unlike, say, smiles, which could indicate happiness), in some ways we are forming an emotional connection by mimicking a yawn or another expression, Campbell said. By mimicking the yawn we see, we become better able to understand how tired, perhaps, or bored the other person is.
In fact, past studies have shown stronger empathetic responses of all kinds toward kin and loved ones. Past research has also found kids with autism don't experience contagious yawning, also strengthening its ties with empathy since autism involves problems with social interaction and communication. On the other hand, canine pals can catch yawns from humans, suggested a study on various dog breeds.
How catchy are yawns?
"Yawning contagion" has been studied among various primate species, with most of the studies occurring in lab settings. In the new study, by contrast, Ivan Norscia and Elisabetta Palagi of the University of Pisa in Italy observed adults in various natural settings, including restaurants, workplaces, waiting rooms and their homes.
The 109 adults in the study were from Europe, North America, Asia and Africa, and they were about evenly split by gender. The researchers were able to analyze 480 bouts of yawns. After considering for factors that could have affected the time between a person's yawn and an observer's imitation, they found social bond was key.
To avoid confusing a spontaneous yawn for one triggered by another person, the researchers limited their recording time to three minutes. In about two-thirds of the cases, relatives of the yawner responded with their own yawn within a minute, as did about half the friends of the yawner.
Most strangers and acquaintances took two or three minutes to respond, Norscia told LiveScience.
"Not only is contagion greater between familiar individuals, but it also follows an empathic gradient, increasing from strangers to kin-related individuals," Norscia and Palagi wrote online Dec. 7 for the journal PLoS ONE. [8 Humanlike Behaviors of Primates]
Thinking about using yawning as a way to determine your empathetic friends? Norscia told LiveScience in an email that during his and Palagi's study, she was "complaining because her husband had responded to a couple of yawns from one of her friends (a woman) – but that was just a joke." He noted that empathy is subjective and that yawning can be influenced by various factors, including boredom or fatigue.
Meaning of yawns
While the results suggest empathy causes one person to catch another's yawn, they don't tell us whether the phenomenon was specifically adaptive to our ancestors and passed down to modern humans. One idea supporting this adaptive theory is that coordinated behaviors would have been crucial for our primate relatives.
"If getting sleepy and climbing up into the trees as a refuge safe from predators" was practiced by our ancestors, and if yawning facilitated that behavior, it makes sense yawning would be evolutionarily selected for, said Euclid O. Smith of the anthropology department at Emory University. "He who yawns last might be dinner for a predator." Smith wasn't involved in the new study.
There's also a chance that catchy yawns were just a byproduct of other mimicked expressions, Campbell told LiveScience. Perhaps we copied others' smiles and frowns first, which led us to do the same for yawning even though that particular behavior wasn't selected for specifically over the course of human evolution.
Either way, researchers still seem mystified by yawning contagion.
"Very little is known about the function of contagious yawning," said Atsushi Senju of the Center for Brain and Cognitive Development at Birkbeck College in London. Senju, who was not involved in the study, told LiveScience: "It might be useful to coordinate the level of alertness within the group, but there is no evidence supporting it. Or it could be a byproduct of empathy — closely attending to family and friends and [feeling] for them, which would help maintain relationship."