Why are yawns contagious?
Scientists are still working it out. Seeing a yawn triggers an automatic response in the brain’s motor cortex, and yawns spread most easily between people who are close.
Quick Answer
Scientists don’t have a complete answer, but they’ve learned a lot. A 2017 University of Nottingham study in Current Biology found that catching a yawn is tied to how excitable a person’s primary motor cortex is, the part of the brain that controls movement, and that telling people to resist yawning actually made the urge stronger. Yawns also spread along social lines: a 2011 study in PLOS ONE found they were most contagious between relatives, then friends, then acquaintances, and least between strangers. That has led some researchers to link contagious yawning to empathy, but a 2014 Duke University study of 328 people found empathy didn’t explain who caught yawns. Age was the only factor that stood out, with contagious yawning declining as people got older. Even dogs can catch human yawns: in a 2008 study, 21 of 29 dogs yawned after watching a person yawn.
By the Numbers
Key Facts
- Short answer
- Scientists aren’t sure, but it’s partly an automatic brain response
- Brain link
- Tied to how excitable the motor cortex is, a 2017 study found
- Social link
- Yawns spread most between relatives and friends
- Surprise
- Dogs can catch human yawns too, in one small study
Who catches a yawn most easily
| Relationship | How contagious |
|---|---|
| Relatives | Most |
| Friends | Very |
| Acquaintances | Less |
| Strangers | Least |
From a 2011 study in PLOS ONE that recorded people’s yawns in everyday settings.
A reflex in the brain
In the 2017 Nottingham study, volunteers watched videos of people yawning while researchers measured activity in their motor cortex. People with more excitable motor cortexes were more likely to catch yawns, and being told to resist only made the urge stronger.
Closer bonds, more yawns
Researchers in Italy recorded yawns in everyday life and found they spread most readily between relatives, then friends, then acquaintances, and least between strangers.
Is it empathy?
Because yawns spread between people who are close, many scientists suspected a link to empathy. But when Duke University researchers tested 328 volunteers, empathy, tiredness and energy levels didn’t predict who caught yawns. Only age did, and most of the variation remains unexplained.
Not just humans
In a 2008 study published in Biology Letters, 21 of 29 dogs yawned after watching a person yawn, while none yawned at other mouth movements.
Myth vs. Fact
MythOnly tired people catch yawns.
FactIn the Duke study, tiredness and energy levels didn’t predict contagious yawning. Age did.
MythYou can just decide not to catch a yawn.
FactTrying to resist made the urge stronger in the 2017 Nottingham study.
The Bottom Line
Yawns are contagious partly because of an automatic response in the brain’s motor cortex, and they spread most easily between people who are close. Why we evolved to catch them is still an open question.
Sources & Further Reading
- Current Biology — A Neural Basis for Contagious Yawning (2017)
- University of Nottingham — Yawning: why is it so contagious and why should it matter? (2017)
- PLOS ONE — Yawn Contagion and Empathy in Homo sapiens (2011)
- PLOS ONE — Individual Variation in Contagious Yawning Susceptibility Is Highly Stable and Largely Unexplained by Empathy or Other Known Factors (2014)
- Biology Letters — Dogs catch human yawns (2008)