People laugh for a lot of different reasons. We laugh when something is funny, like a joke. We laugh when something surprises us, like someone slipping on a banana peel and falling on their butt. We laugh when someone tickles us. We sometimes even laugh when we're nervous or scared! Scientists don’t yet know all the reasons why so many different things cause us to laugh. But we do know laughter helps us to get along with each other.
In some ways, laughing is a way of talking. The ancestors of humans were laughing long before they had language. Before words, laughter could let others know: “Everything is OK!” Today, we still laugh as a way to let other people know that we like them, that we’re friendly, and that we’re part of a group. In fact, did you know that you can “catch” laughter from another person? Yep, even the sound of another person’s laugh can make someone start laughing. That’s a good thing, because laughter is healthy for us!
Laughter causes the release of special chemicals in your brain that help you relax and feel good. Laughing is exercise: It makes you breathe deeply, use your muscles, and get your heart and lungs going. All of this can calm you down if you’re feeling worried or scared. Scientists think laughing may also help boost your immune (ih-MYOON) system (which helps your body to fight off sickness), ease pain when you are hurt, and put you in a good mood.
Watch as one woman’s laughter spreads through a train car until everyone is laughing. Try not to giggle yourself—it’s hard!