Tickling

[sabrinah]

How does tickling work? How come some people are ticklish and others arne't? If you are ticklish, why does it only work when someone else does it?

[jbeputnam]

Tickling works by stimulating receptors in/under the skin. Some people are more sensitive than others, simply because that's the way it goes. When someone else tickles you, it comes as a surprise. Don't ask me why, but when you do it to yourself, your body knows you're doing it, and isn't surprised.

[Isaacr]

Or look at: article 746 a longer explanation