Ask A Scientist

When I tickle myself, why don't I feel it?

Asked by: Aliyah Badr
School: St. John the Evangelist
Grade: 6
Teacher: Anu Rai
Hobbies/Interests: Reading, drawing

 

Answer from Siva Adusumilli

Research Assistant and PhD Candidate

Research area: Thin films, semiconductors, nano materials and solar cells
Interests/hobbies: Volunteering, playing with kids, listening to music and cooking

The word tickle came from the Middle English word "tikelen," which means "to touch lightly." Tickling makes people giggle or cringe sometimes, but mostly it makes people laugh. It is a sense of touch on the skin, and the nerve endings of the skin transmit messages to the brain that reach the cerebellum (the back bottom side of the brain), which regulates the initiation of movement in the body. The cerebellum activates only upon an unexpected touch (i.e. when tickled by someone and not ourselves.) When you tickle yourself, the cerebellum predicts the sensation and this prediction is used to cancel the response of other brain regions to the tickle. This is why you do not feel the tickle sensation when you tickle yourself. But, when touched/tickled by someone else, the cerebellum cannot predict this, and your body produces a tickling sensation and responds by a shrug or cringe.

The feeling of a tickle is processed by two regions in the brain — the somatosensory cortex, which processes touch, and the anterior cingulated cortex, which processes the pleasant information. Researchers have fond that these two regions are less active (mostly passive) when we try to tickle ourselves versus someone else tickling us. This explains why we actually feel awkward when we tickle ourselves rather than feeling tickly and pleasant.

Besides being fun, the other important function of tickling is to work as our body’s alarm system. Tickling protects us by drawing our attention to external predators and parasites, like bugs and flies. This type of tickling is called knismesis, although it rarely produces laughter. This reaction is shared by both humans and animals. Imagine a dog flipping its tail in response to a pesky fly or a human instantly whacking his arm when a bug lands on his skin.

You can actually block a tickle in advance. Try this trick by placing your hand on the tickler’s hand. In doing so, you generate the same motion as the tickler, which makes your brain think that you’re the one doing the tickling. This is a trick used by doctors, who put your hand on yours when they examine your belly so that you won’t feel tickled!  

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Last Updated: 9/25/14