Why It's Impossible To Tickle Yourself

If you've ever taken part in a tickle fight, the winner usually has the advantage of surprise on their side. That's because the effectiveness of a tickle depends on the element of unpredictability. A tickle can be such an overwhelming sensation that it can result in uncontrollable laughter or gasping for air. So why is it that when you dig your fingertips into your own side, you're unable to evoke that same giddy response?

Neuroscientist Sarah-Jayne Blakemore from University College London in the UK explains that tickling can actually be split into two categories (via Science Alert). The first, gargalesis, is intense and often results in the aforementioned hysterical laughter and difficulty breathing. The second type, knismesis, is lighter and feels akin to a small insect crawling up your leg. 

According to experts at The Conversation, warding off bugs is actually one of the objectives of our body's tickle response. Throughout evolution, early humans were able to avoid infection from potentially poisonous insects when their body hair detected their presence. This allowed those who were more ticklish to have a longer lifespan than those who were not, as those who were not were more susceptible to dangerous bug bites.

The area of our brain responsible for the tickle response is the cerebellum (via Scientific American). The cerebellum performs a variety of functions, like the regulation of timing and motor movement (via UT Health). Because of this, our brains are able to anticipate our next move before we make it. A study conducted by researchers at Queen's University found that self-administered physical stimuli were less perceived by the brain than stimuli administered to participants from an external source (via Science Daily). This occurrence is known as sensory attenuation and results in our brain deactivating our own tickle response.

Try as we might, it's not possible to outsmart our own brains. Tickling serves a specific physical purpose when it comes to detecting danger, but it also plays a role in our emotions as well. Studies have found that the same part of our brain is stimulated when we're tickled as when we hear a funny joke. Therefore, tickling can serve multiple purposes — as long as we don't see it coming.