But did you ever notice that some parts of your body were more ticklish than others? A surprise tickle on the side of your stomach would have you giggling instantly but the same thing done on the top your head won't. Also, no matter how hard you tried, you could never tickle yourself and have the same sensation as when one of your friends did that to you.
The reaction to tickling is one of the strangest response of the human body. Many scientists over the past few decades have studied the human reactions to tickling. Although they have not been able to establish a relation between tickling and humour, they've found that laughter and tickling are connected, via nerve stimulation and brain activity.
So let's see what happens when you are tickled. The outermost layer of your skin is known as the epidermis. And the epidermis is bundled with many nerve endings. When stimulated, these nerve endings engage two parts of your brain - one that analyzes the touch, and the other that regulates pleasurable feelings.
Usually, the most ticklish parts of your body are the ones that are least protected by bones (like the stomach and bottom of your feet). This makes sense because scientists believe that tickling is related to defending oneself. As a response to tickling, the brain launches into the fight or flight mode. Thus, the squirming that accompanies tickling is also a form of instinctive defence mechanism, to compress that part of the body and reduce the area available to attack.
Now, let's come to the other part. Why can't you tickle yourself? Simply put, you can't tickle yourself because you can't surprise yourself. A great deal of response to tickling comes from the element of surprise and a foreign object coming in contact with those sensitive areas. If you try to tickle a vulnerable area of your body, your brain already knows it, and it controls the exact location, speed and the duration of the 'tickle'.
The brain perceives no credible threat, so the fight or flight response isn't engaged. Although, there is a type of tickling reaction, known as knismesis, which is the reaction we have when the skin is lightly stimulated, which often generates an “itch”. The reaction to gently rubbing a feather on your skin can generate that kind of itch, but it will hardly get you down on the floor in splits, as in the case of a full-on tickle attack.
Now that you know all this, go and have more tickle fights. Find out the weak spots in your opponents, and tickle them to the ground.