The word ‘tickle’ is derived from the Old English word tinclian meaning ‘to touch lightly’. Tickling can be divided into two classes of sensation: Knismesis is a mild sensation caused by a light movement on the skin, such as from a crawling insect, that doesn’t produce laughter and is often accompanied by an itching sensation. Gargalesis refers to a harder, laughter-inducing movement, and involves the repeated application of high pressure to sensitive areas.
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. A German study also indicates that the gargalesis type of tickle triggers a defense mechanism for humans in the hypothalamus conveying submissiveness or fleeing from danger.
It might be tempting to speculate that areas of the skin that are the most sensitive to touch would also be the most ticklish, but this does not seem to be the case. While the palm of the hand is far more sensitive to touch, most people find that the soles of their feet are the most ticklish. Other commonly ticklish areas include the sides of the torso, underarms, ribs, midriff, neck, back of the knee, thighs, buttocks, and perineum. Some evidence suggests that laughing associated with tickling is a nervous reaction that can be triggered; indeed, very ticklish people often start laughing before actually being tickled.
Picture Credit : Google
