Tickling is a type of light touching that produces a tingling sensation, which often results in laughter, smiling, and involuntary twitching. Scientific studies suggest that this tickle response is an innate (inborn) response. The most ticklish parts of the body are the underarms, waist, ribs, and feet, followed by the knees, throat, neck, and palms.
Scientists do not know why tickling causes laughter. But they do know that laughter stimulates the release of endorphins, chemicals in the brain that produce a feeling of well-being. Tickling, such as light touches under the arms or a playful jab to the ribs, reinforces psychological closeness between people through physical touch. Throughout the world, playful children, parents with babies, and couples in love often give and receive tickling.
Tickling can be pleasant or unpleasant. Although tickling usually produces laughter, most people say they dislike being tickled. During the Middle Ages, prolonged tickling was sometimes used as a form of torture. Tickle sensations travel through the body along the same nerves that transmit impulses for pain and itching. People often respond to tickling the same way as to pain or itching, by withdrawing and scratching.
People usually cannot cause laughter by tickling themselves. Scientists believe that people cannot tickle themselves because the brain anticipates (expects) the tickling, which eliminates the necessary element of surprise that leads to laughter.
