system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we laugh when being tickled but we don't like being tickled?
gpt
Laughter when being tickled is a reflexive response, and primarily a defense mechanism. It's no coincidence that the most ticklish parts of the average human are also the most vulnerable spots (neck, etc). 

People don't laugh when they're tickled because they find it funny, it's more of a submissive gesture as part of the defense mechanism. Scientists have done studies on tickling and when they scanned the brains of people being tickled, they saw that the hypothalamus-- the part of the brain governing more primal functions like breathing, heartbeat, and the fight-of-flight response-- is what really lit up.

This coincidentally explains why it's not possible to really tickle yourself-- if you're doing it to yourself, there's no reason to have the typical defensive response.