Science Mysteries: Why Do People Yawn?


Recent studies suggest that we yawn when we get tired as a way to encourage our brains. The theory is that yawning helps cool the brain, allowing it to work more efficiently. According to WebMD's article about these studies, when you yawn, your jaw muscles get stretched, increasing blood flow to your neck, face, and head. Also a deep breath during the yawn forces spinal fluid and blood down from the brain. The cool air then cools down these fluids.


Which line shows the main idea of the paragraph?


We yawn when we get tired as a way to encourage our brains

When you yawn, your jaw muscles get stretched

Also a deep breath during the yawn forces spinal fluid and blood down

The cool air then cools down these fluids.