Why Are Yawns Contagious?

Lots of animals yawn. It's a primitive reflex. Humans even begin to yawn before birth, starting about 11 weeks after conception. But contagious yawning doesn't start until about age 1 or 2. And even though yawning is used as a social signal by other animals, there's no clear evidence that yawning is contagious for other animals the way it is for humans. Your cat can yawn, and you may yawn when you see her yawn; she, however, won't yawn if she sees you do so.

A recent report in the journal Cognitive Brain Research links yawning to the evolution of the human capacity for empathy. The authors of this report hypothesized that the contagious effect of a yawn might have something to do with theory of mind - the ability to infer other people's thoughts, feelings, and intentions from their actions. Theory of mind is what allows us to have empathy - to imagine what it's like to walk in another guy's shoes- and it's also closely tied to another uniquely human skill, self-awareness.

How would you test the hypothesis that contagious yawning really does result from a particularly human cluster of abilities underlying empathy and self-awareness? One way might be to see if people who are particularly prone to 'catching' a yawn after seeing someone yawn on a video also score high on measures of self-awareness and the ability to draw inferences about other people's mental states. In this recently published experiment, that is exactly what turned out to be the case. In other words, in several tests, people more susceptible to contagious yawns ranked higher in self-awareness and cognitive skills related to empathy. Who would have imagined that something as commonplace as a yawn could provide insight into such a noble human impulse? It just goes to show that if you pay attention and ask the right questions, even most boring things in life can yield new insights from time to time.

About the Author

David Gamon, PhD

David GamonDr. David Gamon, one of the original writers at ScienceIQ, studied cognitive science at U.C. Berkeley, where he received his Ph.D. in Linguistics in 1997. He is the author of many popular books about the human brain, including Building Mental Muscle, Use It Or Lose It!, and Brains That Work a Little Bit Differently. His current projects include books about gender differences in the brain, the brain’s construction of sensory reality, and psychopathy.