How do you interpret a yawn? Whether a sign of fatigue or boredom, psychologists say yawning is contagious, yet not all people are susceptible. A new study based on five years of direct observation finds mirroring another's yawn happens more often between friends and family than strangers, more often for women than men.

According to the Italian researchers, their work “supports the hypothesis that this phenomenon has an empathic basis.” So are women simply more empathic than men?

Humans, In the Wild

You’re strap-hanging in the subway when the man pressed against you yawns, and suddenly you find yourself unable to resist the urge to open wide. Though brief — on average just 6 seconds long — yawns are contagious, the researchers explain. Previous studies suggest our yawn responses occur within 5 minutes after watching a “trigger yawn,” with our desire to mimic another's yawn peaking in the first minute. Yet, under laboratory conditions, roughly 40 to 60 percent of study participants are never observed to follow a trigger yawn. Clearly, not everyone is susceptible to the contagion, but is the same true in the real world?

Biologists at the Natural History Museum, Pisa, Dr. Ivan Norscia, lead author, and Dr. Elisabetta Palagi, senior author, gathered data from 2010 to 2015 on humans in the wild. Surreptitiously, the scientists watched and recorded instances of yawning among women and men in offices, train stations, over dinner, and during social events. Familiar to the researchers, study subjects were all at least 17 years old and their relationships with others in any given scenario were known.

Coming out from behind potted plants, Norscia and Palagi assembled to discuss and analyze the data. They discovered rates of yawning to be highest among strongly bonded subjects. Couples, friends, and family, then, were more likely to yawn in tandem than acquaintances or strangers. Yet, they also found rates of contagion to be “significantly higher in women than in men.”

Men caught a yawn on 40 percent of occasions, while women did so nearly 55 percent of the time.

The researchers, who worked with doctoral student Elisa Demuru, explain chimpanzees and bonobos are also more likely to mirror yawns among in-group than out-group members. You got it: Monkey see, monkey do. Though scarce, studies examining sex differences in empathy also suggest women are more sensitive than men to others’ emotions and so more likely to mimic certain (but not all) facial expressions. In light of the existing evidence, then, the team says their study “further supports the empathic ground of yawn contagion.”

Having greater reserves of empathy, women apparently find themselves susceptible to various forms of emotional contagion from their companions. Sadly enough, this even includes the fleeting expression of another's boredom.

Source: Norscia I, Demuru E, Palagi E. She more than he: gender bias supports the empathic nature of yawn contagion in Homo sapiens. Royal Society Open Science. 2016.