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Tickling〔(【引用サイトリンク】title=Tickling )〕 is the act of touching a part of a body in a way that causes involuntary twitching movements or laughter. The word evolved from the Middle English ''tikelen'', perhaps frequentative of ''ticken'', to touch lightly.〔 The idiom ''tickled pink'' means to be pleased or delighted.〔(Etymology of "tickle" )〕 In 1897, psychologists G. Stanley Hall and Arthur Allin described a "tickle" as two different types of phenomena.〔Hall, G. S., and A. Allin. 1897. ''The psychology of tickling, laughing and the comic.'' The American Journal of Psychology 9:1-42.〕 One type is caused by very light movement across the skin. This type of tickle, called a knismesis, generally does not produce laughter and is sometimes accompanied by an itching sensation. The question as to why a person could not tickle themselves was raised by the Greek philosopher Aristotle. Francis Bacon and Charles Darwin believed that humorous laughter requires a "light" frame of mind. But they differed on ticklish laughter: Darwin thought that the same light state of mind was required, whereas Bacon said no. When tickled, noted Bacon, "men even in a grieved state of mind, yet cannot sometimes forbear laughing."〔Darwin, C. 1872/1965. The Expressions of the Emotions in Man and Animals. London: John Murray.〕 ==Physiology== When considering tickling in terms of its qualities as a sensation, it results from a mild stimulation moving across the skin. The dual character of tickling refers to the associated behaviours that include smiling, laughter, withdrawal and goose bumps. The tickle can be divided into two separate categories of sensation, knismesis and gargalesis. Knismesis, also known as a "moving itch", is a mildly annoying sensation caused by a light movement on the skin, such as from a crawling insect. This may explain why it has evolved in many animals. Gargalesis reactions refers to a pleasurable, laughter-provoking feeling caused by a harsher, deeper pressure, stroked 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. It appears that the tickle sensation involves signals from nerve fibres associated with both pain and touch. Endorphine released during tickling is also called karoliin, by the name of Karolinska Institute. In 1939, Yngve Zotterman of the Karolinska Institute studied the knismesis type of tickle in cats, by measuring the action potentials generated in the nerve fibres while lightly stroking the skin with a piece of cotton wool. Zotterman found that the "tickling" sensation depended, in part, on the nerves that generate pain.〔Zotterman, Y. 1939. "(Touch, pain and tickling: An electrophysiological investigation on cutaneous sensory nerves. )" ''Journal of Physiology'' 95:1-28.〕 Further studies have discovered that when the pain nerves are severed by surgeons, in an effort to reduce intractable pain, the tickle response is also diminished. However, in some patients that have lost pain sensation due to spinal cord injury, some aspects of the tickle response do remain. Tickle may also depend on nerve fibres associated with the sense of touch. When circulation is severed in a limb, the response to touch and tickle are lost prior to the loss of pain sensation.〔 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, some people find that the underarms are the most ticklish.〔 Other commonly ticklish areas include the feet, sides of the torso, neck, knee, midriff, perineum, navel, and the ribs. 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tickling」の詳細全文を読む スポンサード リンク
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