20/20: Are Yawning and Laughing Contagious?

July 12 -- Think about your eyes getting watery, perhaps your nose crinkling up a bit, hands stretching above your head and mouth opening wide as you take about a six-second inhalation. Make you want to yawn?

According to Robert Provine, professor of psychology at the University of Maryland Baltimore County, it’s no surprise if it does.

“Yawning is extraordinarily contagious,” says Provine, who has published much of what is known about the subject, particularly its behavioral aspects. “Seeing a person yawn triggers yawns. Reading about yawning causes yawns. Sitting alone in a room thinking about yawning triggers yawning.”

A brain mechanism, Provine explains, actually detects a yawning face, which then triggers that behavior. “Once the neurological machinery in our head gets underway,” he says, “it’s hard to stop a yawn.”

Not Just a Matter of Oxygen

The common theory about why we yawn is to get more oxygen to our brains. But according to Provine, it is not so simple. In scientific experiments, he discovered that even with 100 percent oxygen, his subjects yawned just as much as when they had less.

Yawning, says Provine, which occurs as early as the first trimester of prenatal development, is about transitions in the body’s biology. Of course, one of those changes is from a state of alertness to a state of sleepiness. But surprisingly, yawning can also be a behavior that marks a transformation from sleepiness to alertness.

“At track and field events,” says Provine, “sometimes you’ll find participants in the race of their life will be standing around on the sidelines or in the starting block and they may be yawning.” Or, for example, before a concert, a musician may yawn to prepare for an increasingly energized state.

Yawning is also a way for people to synchronize group behavior. “When you see someone yawn, you’re initiating a chain reaction of biology,” Provine says. “So whatever changes in our body are brought about by yawning, are synchronized in everyone that’s doing it.”