Stop reading for a second and try to tickle yourself. It didn’t work, did it? Isn’t that strange? If you think about it, it’s rather odd that you feel nothing when you tickle your own underarms, and yet—someone else’s touch could easily make you squirm, giggle, and shriek. So why can’t you tickle yourself?
How Tickling Works
Under your skin are millions of nerve endings that send signals to your brain. This is how you experience physical sensations—such as the softness of a dog’s fur or the discomfort of a rock in your shoe. When these nerves are lightly touched (like with tickling), they stimulate two regions of the brain: the somatosensory cortex, which processes touch, and the anterior cingulated cortex, which processes happiness or pleasant feelings.
This causes the brain to process tickling as one of two types of sensations: Knismesis or gargalesis. Knismesis is a reaction to a very light sensation—such as when a hair or feather brushes against your skin. This feeling can lead to goosebumps, giggling, or shivers. Gargalesis is the reaction to an intenser version of this light touch—like when your older brother holds you down and tickles you so hard you feel like you’re going to explode.
While both of these reactions elicit laughter, it’s not necessarily because we enjoy the associated feeling. Evolutionary scientists believe that we may laugh while being tickled as a way to signal submissiveness to a potential attacker, or even as a method of social bonding. Think about it for a moment. Some of the most ticklish areas of our bodies—the neck, ribs, and underarms—are also the most vulnerable. It makes sense that we wouldn’t want someone who is handling those areas to think we’re a threat!
Why We Can’t Tickle Ourselves
There’s still a fair amount of mystery surrounding the question as to why our nerves react differently when we tickle ourselves, but most scientists point to the cerebellum’s ability to predict what’s going to happen.
The cerebellum is located at the base of the brain and monitors our movements, with the ability to distinguish between expected and unexpected motions. To help us get through life without being overwhelmed with sensations, this part of the brain essentially “throws out” expected sensations that aren’t deemed dangerous. So every time we decide to tickle ourselves, the cerebellum decides in turn that we don’t need to react to the pressure—thus, we feel nothing upon contact.
The key to being properly tickled is the element of surprise. Otherwise, it won’t work.