The Brain's Reward System
Laughter starts in the brain's 'reward center.' When you hear a joke or see something funny, your brain releases dopamine, a chemical that makes you feel happy.
This creates an instant 'high' that tells your body to start the physical process of laughing.
The Vocal Gush
Physically, a laugh is just a very specific way of breathing. Your diaphragm (the muscle under your lungs) starts to spasm, forcing air out of your lungs in short, rhythmic bursts.
As this air passes over your vocal cords, it creates the 'ha-ha' or 'he-he' sounds. Because you are exhaling so much air, you often can't speak while laughing hard!
The Social Glue
Laughter is actually 30 times more likely to happen when you are with other people than when you are alone. It acts as 'social glue.'
It signals to others that you are safe, friendly, and that you are part of the group. It is a universal language that everyone on Earth understands.
A Natural Painkiller
When you laugh, your body releases endorphins. These are the body's natural feel-good chemicals that can actually dull physical pain.