A person starts laughing. The joke is not even that good. Ten seconds later everyone else is gone.
Laughter behaves differently from a private reaction to humor. It is strongly social, can spread through sound alone, and appears to help coordinate relationships as much as it comments on what is funny.
The sound itself recruits a response
Laboratory work has shown that hearing laughter can trigger contagious responses even without another person physically present. Brain-imaging research also finds that laughter sounds engage networks linked with auditory-motor processing and social perception.
Laughter is physical behavior
Exhalation becomes rhythmic
Laughter repeatedly interrupts normal breathing patterns.
Multiple facial muscles join
The expression is part vocal signal, part visible signal.
Pitch and timing change rapidly
Those acoustic features carry information about spontaneity and social intent.
The behavior may support affiliation
Studies link social laughter with mechanisms involved in social bonding.
The funniest clips share one feature
The laugh becomes the content. A person tries not to laugh. Someone hears the laugh and loses control. A third person joins without knowing why. The original joke becomes almost irrelevant.
Sometimes laughter is communication wearing a comedy costume
We laugh because something is funny.
We also laugh because someone else is laughing, because a group is connected, because tension is breaking, or because the social moment needs a signal.
The audience changes the behavior
Shared laughter is bonding
Research has linked social laughter with increased feelings of social connection.
Even unfamiliar company can change laughter
Classic experiments found people laughed more in some social conditions than when watching the same humorous material alone.
Conversation laughter is common
Humans laugh during ordinary social interaction, not only after punchlines.
We hear different kinds of laughter
People distinguish spontaneous laughter from more deliberate social laughter with imperfect but meaningful cues.