Question

when someone tickles why how do we laugh

Answer 1

Hii...

Tickling causes a sensation of laughter as when we experiance a slight touch hypothalamus part of the brain gets activated and signals to laugh.
Hypothalamus is also responsible for the sensation of pain .

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Hope this helps!

Answer 2

When someone tickles us, we laugh and that laugh is actually our response to this danger. This is why we don't laugh when we tickle ourselves.