Knismesis and gargalesis are the

scientific term Scientific terminology is the part of the language that is used by scientists in the context of their professional activities. While studying nature, scientists often encounter or create new material or immaterial objects and concepts and are comp ...

s, coined in 1897 by

psychologist A psychologist is a professional who practices psychology and studies mental states, perceptual, cognitive, emotional, and social processes and behavior. Their work often involves the experimentation, observation, and interpretation of how indi ...

G. Stanley Hall Granville Stanley Hall (February 1, 1846 – April 24, 1924) was a pioneering American psychologist and educator. His interests focused on human life span development and evolutionary theory. Hall was the first president of the American Psy ...

and

Arthur Allin Arthur is a common male given name of Brythonic origin. Its popularity derives from it being the name of the legendary hero King Arthur. The etymology is disputed. It may derive from the Celtic ''Artos'' meaning “Bear”. Another theory, more w ...

, used to describe the two types of

tickling 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. In 1897, psycholo ...

. Knismesis refers to the light, feather-like type of tickling. This type of tickling generally does not induce

laughter Laughter is a pleasant physical reaction and emotion consisting usually of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter ...

and is often accompanied by an

itch Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasant ...

ing sensation. Gargalesis refers to harder, laughter-inducing tickling, and involves the repeated application of high pressure to sensitive areas. While the two terms are used in academic papers, they do not appear in many dictionaries and their origin is rarely declared. The term ''knismesis'' comes from the Ancient Greek () meaning 'itching'. The term ''gargalesis'' stems from the Ancient Greek () meaning 'to tickle'. The suffix '' -esis'' is used to form nouns of action or process.

Knismesis

The knismesis phenomenon requires low levels of stimulation to sensitive parts of the body, and can be triggered by a light

touch In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), and pain. It is ...

or by a light

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

. Knismesis can also be triggered by crawling

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s or

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s, 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. In a famous example, described in

Peter Benchley Peter Bradford Benchley (May 8, 1940 – February 11, 2006) was an American author, screenwriter, and ocean activist. He is known for his bestselling novel ''Jaws'' and co-wrote its film adaptation with Carl Gottlieb. Several more of his works w ...

's ''Shark!'', it is possible to tickle the area just under the snout of a

great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is nota ...

, putting it into a near-

hypnotic Hypnotic (from Greek ''Hypnos'', sleep), or soporific drugs, commonly known as sleeping pills, are a class of (and umbrella term for) psychoactive drugs whose primary function is to induce sleep (or surgical anesthesiaWhen used in anesthesia ...

trance Trance is a state of semi-consciousness in which a person is not self-aware and is either altogether unresponsive to external stimuli (but nevertheless capable of pursuing and realizing an aim) or is selectively responsive in following the dir ...

Gargalesis

The gargalesis type of tickle works on

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

s (which include

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

s), and possibly on other species. 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. However, adult female rats may find the tickling sensation adverse. Because the

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

s 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. While it is possible to trigger a knismesis response in oneself, it is usually impossible to produce gargalesthesia, the gargalesis tickle response, in oneself. Hypergargalesthesia is the condition of extreme sensitivity to tickling. The words knismesis and gargalesis were both used by

Susie Dent Susie Dent (born 1964) is an English lexicographer, etymologist, and media personality. She has appeared in "Dictionary Corner" on the Channel 4 game show ''Countdown'' since 1992. She also appears on ''8 Out of 10 Cats Does Countdown'', a post ...

in an episode of the BBC game show, '' Would I Lie to You?'' (Season 11, episode 4).

References

{{Reflist Reflexes Perception Tickling 1890s neologisms