Neuroscientists have explained why people don't laugh when they tickle themselves.

German neuroscientists have tried to figure out why people don't laugh when they tickle themselves. After experimenting with 12 volunteers, they hypothesized that the brain temporarily blocks touch sensitivity when a person touches their own body. Otherwise, we'd be giggling while putting on socks or scratching our armpits. People with delusions of influence do not have this feature. They are able to laugh, even tickling themselves.