Why Do We Yawn?
The Big Idea
Solve the mystery of the contagious yawn. Discover the latest theories on why we take these deep, involuntary breaths, from cooling down a tired brain to maintaining social connections with those around us.
Key Vocabulary & Concepts
Hands-On Observation Checklist
Teacher & Parent Discussion Starters
- Why is understanding why do we yawn? important in everyday real life?
- What variable or factor had the biggest impact when testing the simulation?
- How does this concept connect to another science topic you have learned about?
Why Do We Yawn?
Solve the mystery of the contagious yawn. Discover the latest theories on why we take these deep, involuntary breaths, from cooling down a tired brain to maintaining social connections with those around us.
Why Do We Yawn?
The Contagious Mystery
I bet that just reading the title of this article made you want to yawn. If you see someone yawn across the room, you will probably yawn. If you see a dog yawn, you might yawn. It is the most contagious human behavior. But why do we do it? For a long time, scientists said: "Oh, it's because you are tired and need more oxygen." They were wrong.
[Diagram: The Brain Radiator] Description: A thermal image style drawing of a head.
- Before Yawn: The brain is glowing Red (Hot).
- Action: Mouth opens wide, deep breath enters nose/mouth.
- After Yawn: The brain turns Blue/Green (Cooler). Caption: Yawning brings in cool air and stretches the jaw, pumping blood away from the hot brain.
The Brain Radiator
The newest and best theory is that a yawn is a Cooling System for your brain. Your brain is a computer. It uses a lot of energy, and it runs hot. When you are tired or bored, your brain temperature actually rises slightly. It gets "overheated" and sluggish.
So, the body triggers a Yawn.
- The Stretch: The massive jaw stretch flexes the muscles in your face. This acts like a pump, pushing warm blood out of the skull.
- The Gulp: The deep intake of cool air chills the blood vessels in the throat and nose.
The result? Cooler blood flows up to the brain. The yawn is a fan kick-starting to cool down the processor so you can focus again. This explains why we yawn when we are tired (fighting to stay awake) or when we first wake up (booting up the system).
The Social Signal
But why is it contagious? Why do I yawn if you yawn? This is likely a primitive form of Social Bonding. Early humans lived in groups. To survive, they needed to be on the same schedule.
- "If I am sleepy, you should be sleepy too so we can all sleep."
- "If I am waking up and alert, you should be alert too."
When one caveman yawned, it triggered a chain reaction that synchronized the group's brain clocks. Interestingly, studies show that you are more likely to catch a yawn from a friend or family member than from a stranger. And psychopaths (people who lack empathy) are immune to contagious yawning!
So, if you just yawned while reading this... don't worry. It just means your brain is hot, and you are a nice, empathetic person.