Knismesis and gargalesis are the scientific terms, 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 explanation, interpretatio ...

G. Stanley Hall Granville Stanley Hall (February 1, 1844 – April 24, 1924) was an American psychologist and educator who earned the first doctorate in psychology awarded in the United States of America at Harvard University in the nineteenth century. His ...

and Arthur Allin, used to describe the two types of

tickling Tickling is the act of Haptic perception, touching a part of a person's body in a way that causes involuntary twitching movements or laughter. The laughter effect is inherently predicated upon the element of surprise, therefore normally does no ...

. 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, usually audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laug ...

and is often accompanied by an

itch An itch (also known as pruritus) is a sensation that causes a strong desire or reflex to scratch. Itches have resisted many attempts to be classified as any one type of sensory experience. Itches have many similarities to pain, and while both ...

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 The somatosensory system, or somatic sensory system is a subset of the sensory nervous system. The main functions of the somatosensory system are the perception of external stimuli, the perception of internal stimuli, and the regulation of bo ...

or by a light

electric current An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...

. Knismesis can also be triggered by crawling

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s or

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

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. He is best known for his bestselling novel '' Jaws'' and co-wrote its movie adaptation with Carl Gottlieb. Several more of his works were also adapted for both ...

'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 Lamniformes, mackerel shark which can be found in the coastal surface waters of all the major ocea ...

, putting it into a near-

hypnotic A hypnotic (from Ancient Greek, Greek ''Hypnos'', sleep), also known as a somnifacient or soporific, and commonly known as sleeping pills, are a class of psychoactive drugs whose primary function is to sleep induction, induce sleep and to trea ...

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 is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

s (which include

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

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). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...

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.

References

{{Reflist Reflexes Perception Tickling 1890s neologisms Quotations from science 1890s quotations