How Jokes Work
The basis of most jokes is that, at the punch line, something disastrous or painful happens to someone. In effect, the unexpected ending 'frightens' our brain, and we laugh with sounds similar to a chimp warning others of imminent danger. Even though we consciously know that the joke is not a real event, our laugh releases endorphins for self-anaesthesis as if the joke was a real event. If it was a real event, we may go into crying mode and the body would also release its endorphins. Crying is often an extension of a laughing bout and is why, in a serious emotional crisis, such as hearing about a death, a person who cannot mentally accept the death may begin laughing. When the reality hits, the laughter turns to crying.
The origin of human laughter is as a primate warning signal
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