Knismesis and gargalesis are the scientific

Science

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

 terms, coined in 1897 by psychologist

Psychology

Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

s G. Stanley Hall

G. Stanley Hall

Granville Stanley Hall was a pioneering American psychologist and educator. His interests focused on childhood development and evolutionary theory...

 and Arthur Allin, used to describe the two types of tickling

Tickling

Tickling is the act of touching a part of the body so as to cause involuntary twitching movements and/or laughter. The word evolved from the Middle English tikelen, perhaps frequentative of ticken, to touch lightly. The idiom tickled pink means to be pleased or delighted.In 1897, psychologists G...

.

Knismesis

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

Laughter

Laughing is a reaction to certain stimuli, fundamentally stress, which serves as an emotional balancing mechanism. Traditionally, it is considered a visual expression of happiness, or an inward feeling of joy. It may ensue from hearing a joke, being tickled, or other stimuli...

 and is often accompanied by an itch

Itch

Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...

ing sensation. The knismesis phenomenon requires low levels of stimulation to sensitive parts of the body, and can be triggered by a light touch or by a light electrical current. Knismesis can also be triggered by crawling insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s or parasites, 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 Benchley

Peter Bradford Benchley was an American author, best known for his novel Jaws and its subsequent film adaptation, the latter co-written by Benchley and directed by Steven Spielberg...

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

Great white shark

The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...

, putting it into a near-hypnotic

Hypnosis

Hypnosis is "a trance state characterized by extreme suggestibility, relaxation and heightened imagination."It is a mental state or imaginative role-enactment . It is usually induced by a procedure known as a hypnotic induction, which is commonly composed of a long series of preliminary...

 trance

Trance

Trance denotes a variety of processes, ecstasy, techniques, modalities and states of mind, awareness and consciousness. Trance states may occur involuntarily and unbidden.The term trance may be associated with meditation, magic, flow, and prayer...

.

Gargalesis

Gargalesis refers to harder, laughter-inducing tickling, and involves the repeated application of high pressure to sensitive areas. This "heavy tickle" is often associated with play and laughter. The gargalesis type of tickle works on human

Human

Humans are the only living species in the Homo genus...

s and primate

Primate

A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

s, and possibly on other species. Because the nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

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 are 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.