Why Does Tickling Cause laughter?

 Tickling (Gudgudi) is the act of touching a part of a body in a way that causes involuntary twitching movements or laughter.

When you're touched, the nerve endings under the top layer of your skin i.e. epidermis, sends electrical signals to the brain. The sensory nervous system picks up the signals relating to pressure, and also analyses the signals. This signal goes to the part of the brain that governs pleasurable feelings (like eating a chocolate).

   

The tickle can be divided into two separate categories of sensation;

Knismesis (say it as Knees-me-Sis) and Gargalesis (Gargle-Sis).

Knismesis, also known as a "moving itch", is a mildly annoying sensation caused due to a light movement on the skin, such as from a crawling insect. This explains how it has evolved in many animals. And the immediate reflex is of being scared and shaking away the source of the tickle.

Gargalesis reactions refer to a pleasurable, laughter provoking feeling caused by a harsher, deeper, pressured stroke across the skin in various regions of the body. These reactions are thought to be limited to humans and other primates, although some research has indicated that rats can also be tickled in this way.

Evolutionary biologists and neuroscientists believe that we laugh when we are tickled because the part of the brain that tells us to laugh when we experience a light touch; the hypothalamus, is also the same part that tells us to expect a painful sensation. Laughing when tickled in our sensitive spots (under the arms, near the throat and under our feet) could be a defensive mechanism.

But surprisingly we can't tickle ourselves because the cerebellum of our brain can predict sensations when our own movement causes them but not when someone else does. When we try to tickle ourselves, the cerebellum predicts the sensation and this prediction cancels the response of other brain areas tickle.

This summers, Happy tickling!