Tickling

The word tickle refers to at least two somewhat distinct phenomena—labeled as knismesis and gargalesis by the prominent late 19th-century psychologist G. Stanley Hall. Knismesis refers to the peculiar sensation, akin to a moving itch, that is produced by something moving lightly across the skin. One can readily produce knismesis in oneself by lightly dragging one’s fingernails across virtually any body area. The annoying sensation can outlast the stimulation by seconds and produces a desire to rub or scratch the stimulated area (doing so tends to obliterate the sensation). This type of tickle usually does not make people laugh. The type of tickle that produces laughter, gargalesis, usually requires a heavier pressure repeatedly applied to specific “ticklish” areas of the body such as the ribcage ...