Steven Chang, MD

Quirky Questions:

Why is yawning contagious?

Why is yawning contagious?

It’s long been known that yawning can be “contagious.” What we don’t know is why, exactly, this behavior occurs (or even why we yawn in the first place). But there are some very plausible theories.

Believe it or not, the act of yawning first occurs in utero. In fact, yawning can be seen on ultrasounds as early as the 11th week of pregnancy. Scientists believe that yawning motions made by a fetus’s mouth and jaw may signal the maturation of certain brain structures.

Beginning around the age of four, we start to yawn when we observe others yawning. This “contagious” yawning coincides with the age when children really begin to become social beings.  Researchers theorize contagious yawning is a type of shared human experience that promotes social bonding, similar to contagious laughter and crying. In fact, brain imaging studies performed when subjects were yawning show increased activity in the parts of the brain believed to be related to empathy, an important emotional capability exclusive to social animals. Furthermore, in a 2010 study, scientists discovered that kids with autism (a disorder in which the affected person may have certain levels of social impairments) were half as likely to be susceptible to contagious yawning.

Due to these types of findings, many researchers now believe that contagious yawning is an automatic behavioral response activated by certain parts of our brains that allowed us to evolve as social creatures. Contagious yawning can occur when we observe someone yawn, hear a yawn, or even see a picture or video of someone yawning. It’s simply an unconscious display demonstrating our ability to empathize. So the next time you catch a contagious yawn, consider it an act of humanly love, not necessarily a response to boredom or fatigue.

Another relatively common theory is that contagious yawning may have evolved as a way of synchronizing the sleep-wake cycles of a family or group of animals. Interesting fact: All vertebrates yawn. However, only humans, chimpanzees, and maybe dogs display contagious yawning.

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