People laugh at jokes.
They also laugh when they are nervous, surprised, relieved, embarrassed, or simply enjoying other people’s company.
That is because laughter is not just a response to humor.
It is also a social and emotional behavior.
Laughter uses several brain systems
The brain coordinates laughter through networks involved in emotion, movement, breathing, and social behavior.
Once laughter begins, muscles in the face, chest, and abdomen contract in a repeating pattern.
Air leaves the lungs in the familiar bursts we hear as laughter.
Why do jokes make us laugh?
Humor often involves surprise, violated expectations, wordplay, absurdity, or recognition.
The exact ingredients vary by culture and person.
Something that makes one person laugh may leave another completely unmoved.
The brain is not running one universal joke detector.
Why do we laugh when we are nervous?
Laughter can appear during tension.
In an awkward situation, a laugh may help reduce emotional pressure or signal friendliness.
That is why someone can laugh at a moment they do not actually find funny.
The response can happen automatically.
Why is laughter contagious?
Hearing other people laugh can prime your own brain to join in.
Humans are highly responsive to social cues.
A joke can feel funnier in a room full of laughing people than when you read the same line silently by yourself.
This helps make laughter a kind of social glue.
Do animals laugh?
Some animals make play-related sounds that researchers compare with laughter.
Rats produce ultrasonic vocalizations during play.
Great apes make breathy sounds during play too.
Human laughter is especially elaborate and social, but the roots of laughter-like behavior may be older than our species.
Why do people keep laughing after the joke is over?
Sometimes the social feedback loop takes over.
One person laughs.
Another person’s laugh becomes funny.
Then everybody is laughing at the fact that everybody is laughing.
Eventually nobody remembers what started it.
So laughter is not just your body’s automatic response to a good joke.
It is part emotion, part communication, and part social glue.
A related piece of human behavior appears in Why do we blush?, where the brain handles another everyday judgment or response.
And that’s the short explanation.
Related explanations: Why do we blush?, Why do we laugh when nothing is funny?, and Why do we get goosebumps?