Punch lines

A punch line ("punch-line" or punchline) concludes a joke; it is intended to make people laugh. It is the third and final part of the typical joke structure. It follows the introductory framing of the joke and the narrative which sets up for the punch line.

In a broader sense punch line can also refer to the unexpected and funny conclusion of any performance, situation or story.

The origin of the term is unknown. Even though the comedic formula using the classic "set-up, premise, punch line" format was well-established in Vaudeville by the beginning of the 20th century, the actual term “punch line” is first documented in the 1920s; the Merriam-Webster dictionary pegs the first use in 1921. Some people argue the term's origin is related to the British weekly magazine Punch.

A linguistic interpretation of the mechanics of the punch line / response is posited by Victor Raskin in his Script-based Semantic Theory of Humor. Humor is evoked when a trigger, contained in the punch line, causes the audience to abruptly shift its understanding of the story from the primary (or more obvious) interpretation to a secondary, opposing interpretation. "The punch line is the pivot on which the joke text turns as it signals the shift between the [semantic] scripts necessary to interpret [re-interpret] the joke text." To produce the humor in the verbal joke, the two interpretations (i.e. scripts) need to be both compatible with the joke text AND opposite or incompatible with each other. Thomas R. Shultz, a psychologist, independently expands Raskin’s linguistic theory to include "two stages of incongruity: perception and resolution." He explains that "… incongruity alone is insufficient to account for the structure of humour. […] Within this framework, humour appreciation is conceptualized as a biphasic sequence involving first the discovery of incongruity followed by a resolution of the incongruity." Resolution generates laughter.

There are many folk theories of how people deliver punchlines, such as punchlines being louder and of a higher pitch than the speech preceding it, and a dramatic pause before the punchline is delivered. In laboratory settings, however, none of these changes are employed at a statistically significant level in the production of humorous narratives. Rather, the pitch and loudness of the punchline are comparable to those of the ending of any narrative, humorous or not.

...
Wikipedia