Knismesis andgargalesis are thescientific terms, coined in 1897 bypsychologistsG. Stanley Hall andArthur Allin,[1] used to describe the two types oftickling. Knismesis refers to the light, feather-like type of tickling. This type of tickling generally does not inducelaughter and is often accompanied by anitching sensation.[2] Gargalesis refers to harder, laughter-inducing tickling, and involves the repeated application of high pressure to sensitive areas.[2]
While the two terms are used in academic papers, they do not appear in many dictionaries and their origin is rarely declared. The termknismesis comes from the Ancient Greekκνισμός (knismós) meaning 'itching'.[3] The termgargalesis stems from the Ancient Greekγαργαλίζω (gargalízō) meaning 'to tickle'.[4] The suffix-esis is used to form nouns of action or process.[5]
The knismesis phenomenon requires low levels of stimulation to sensitive parts of the body, and can be triggered by a lighttouch or by a lightelectric current. Knismesis can also be triggered by crawlinginsects orparasites, prompting scratching or rubbing at the ticklish spot, thereby removing the pest. It is possible that this function explains why knismesis produces a similar response in many different kinds of animals.[2] In a famous example, described inPeter Benchley'sShark!, it is possible to tickle the area just under the snout of agreat white shark, putting it into a near-hypnotictrance.[6]
The gargalesis type of tickle works onprimates (which includehumans), and possibly on other species.[7] For example, ultrasonic vocalizations described as "chirping", which play into social behavior and even have therapeutic effects, are reported in rats in response to human tickling.[8][9][10][11][12] However, adult female rats may find the tickling sensation adverse.[13] Because thenerves involved in transmitting "light" touch and itch differ from those nerves that transmit "heavy" touch, pressure and vibration, it is possible that the difference in sensations produced by the two types of tickle is due to the relative proportion of itch sensation versus touch sensation.[14] While it is possible to trigger a knismesis response in oneself, it is usually impossible to producegargalesthesia, the gargalesis tickle response, in oneself.[2]Hypergargalesthesia is the condition of extreme sensitivity to tickling.[15]
^Burgdorf, J.; Kroes, R.A.; Moskal, J.R.; Pfaus, J.G.; Brudzynski, S.M.; Panksepp, J. (2008). "Ultrasonic vocalizations of rats (Rattus norvegicus) during mating, play, and aggression: Behavioral concomitants, relationship to reward, and self-administration of playback".Journal of Comparative Psychology.122 (4):357–367.doi:10.1037/a0012889.PMID19014259.
^Paredes-Ramos, P.; Miquel, M.; Manzo, J.; Pfaus, J.G.; López-Meraz, M.L.; Coria-Avila, G.A. (2012). "Tickling in juvenile but not adult female rats conditions sexual partner preference".Physiology & Behavior.107 (1):17–25.doi:10.1016/j.physbeh.2012.05.017.PMID22640704.S2CID161288.
