Laughter is an emotional response to emotional tension built-up from the benign violation of expectations.

When a comedian tells a story, he deliberately sets out to create a certain tension in his listeners, which mounts as the narrative progresses. But it never reaches its expected climax. The punch line, or point, acts as a verbal guillotine that cuts across the logical development of the story; it debunks the audience’s dramatic expectations. The tension that was felt becomes suddenly redundant and is exploded in laughter.

— Encyclopedia Britannica

Laughter disposes of the emotive excitations that have become pointless (due to the violated expectation) and need to be released across the physiological channels of “least resistance.”

Physical Characteristics

It involves a stereotypical and predictable set of characteristics:

  • the involuntary contraction of over 15 facial muscles
  • altered breathing
  • it is associated with irrepressible noises

Laughter might be a way to communicate empathy and build better relationships with others. The emotional response (laughter) is so familiar and makes it obvious to the comedian when their audience has understood their message.