Tickle.

Tickle is a familiar sensation that may have two components: a light or feather-type noxious sensation termed by Hall and Allin as knismesis, and a heavy or laughter-associated sensation termed gargalesis. Studies on the sensation of tickle have generally been on one sensation or the other, but not on both. In pleasurable, laughter-associated tickle there are elements of touch and pleasure, but the sensation may be a synthesis of touch and itch, with receptors, neural pathways or central receptors different from knismesis. It is unclear why some skin sites are more ticklish than other sites. Laughter-associated tickle might best be considered a social behavior rather than a reflex. This behavior provides interaction between mother and child, helps to integrate a child with peers and adults in play, and may become part of the mating ritual or sexual foreplay. In tickle play there are elements of dominance and submission, with accompanying laughter and withdrawal developed as the signals of submission. In this scenario, ticklish areas of skin might be considered those areas most vital to the ticklee and allowed to be invaded in the dominance submission play.