Today’s Wonder of the Day was inspired by Tina from Orlando, FL. Tina Wonders, “Why can't you tickle yourself?” Thanks for WONDERing with us, Tina!

Tickle fight!" Those are the words that often start what turns out to be a hilarious free-for-all at a sleepover. After all, who can resist tickling a friend and causing them to guffaw with peals of laughter?

If laughter is the best medicine, then a tickle fight is like a trip to the hospital! Laughing with good friends can make all your troubles and worries disappear for a while. Although you might feel exhausted after a raucous tickle fight, it's refreshing to cackle with your best friends.

But what about when you're alone? Can you have a tickle fight by yourself? Not likely! Why not? Most people find that, even if they try, they can't tickle themselves. What's up with that?

Scientists think that your brain is the culprit. The human brain works amazingly well. In fact, it works too well sometimes, and that's why most people can't tickle themselves.

So that it can focus on the important things going on around you, your brain anticipates and filters out the routine things around you. One such thing it filters out is your own touch. When you go to scratch your arm or rub your leg, your brain already knows what's going to happen before it happens.

A big part of a good tickle is the surprise factor. When someone tickles you unexpectedly, your body has a genuine reaction, which usually includes squealing with laughter. When you try to tickle yourself, there's no surprise factor. Your brain anticipates the touch and isn't surprised when it occurs.

Scientists believe the part of the brain responsible for monitoring the body's movements is the cerebellum. The cerebellum is located at the base of the brain. It automatically distinguishes between expected sensations (like how your pencil feels in your hand when you write) from unexpected sensations (like someone grabbing you from behind).

The cerebellum throws out the unimportant, expected sensations (when's the last time you were aware of how a pencil felt in your hand?), so that it can concentrate more on the unexpected sensations (why you're likely to jump in surprise if someone unexpectedly grabs you from behind). A side effect of the cerebellum's efficiency is that it's very hard to tickle yourself!

Of course, that doesn't mean it's impossible. In fact, some people believe they've identified one area of your body where it is possible to tickle yourself: the roof of your mouth. Give it a try! Does it work? Experts believe it may be possible to tickle yourself by touching the roof of your mouth, because most people aren't used to touching the roof of their mouth!

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Tomorrow’s Wonder of the Day is especially patriotic!