Goose bumps

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This article is about the bumps that form on skin. For the book series by R. L. Stine, see Goosebumps.

Goose bumps (AE), also called goose pimples, goose flesh (BE), chicken skin (Hawaiian Pidgin), or cutis anserina, are the bumps on a person's skin at the base of body hairs which involuntarily develop when a person is cold or experiences strong emotions like fear or awe. The reflex of producing goose bumps is known as horripilation, piloerection, or the pilomotor reflex. It occurs not only in humans but also in many other mammals; a prominent example are porcupines which raise their quills when threatened.

Goose bumps are created when tiny muscles at the base of each hair, known as arrectores pilorum, contract and pull the hair erect. The reflex is started by the sympathetic nervous system, which is in general responsible for many fight-or-flight responses.

Goose bumps are often a response to cold: in animals covered with fur or hair, the erect hairs trap air to create a layer of insulation. Goose bumps can also be a response to anger or fear: the erect hairs make the animal appear larger, in order to intimidate enemies. This can for example be observed in the intimidation displays of chimpanzees<ref>Martin Muller and John Mitan. Conflict and Cooperation in Wild Chimpanzees. Advances in the Study of Behavior, vol. 35</ref>, in stressed mice<ref>Masuda et al. Developmental and pharmacological features of mouse emotional piloerection. Experimental Animals, 1999 Jul;48(3):209-11. PMID 10480027</ref> and rats, and in frightened cats. In humans, it can even extend to piloerection as a reaction to hearing nails scratch on a chalkboard or listening to awe-inspiring music.<ref>David Huron. Biological Templates for Musical Experience: From Fear to Pleasure. Abstract</ref>

Piloerection as a response to cold or fear is vestigial in humans; as humans retain only very little body hair, the reflex now serves no known purpose.

In humans, goose bumps are strongest on the forearms, but also occur on the legs, back, and other areas of the skin that have hair. In some people, they even occur in the face or on the head.

Piloerection is also a (rare) symptom of some diseases, such as temporal lobe epilepsy, some brain tumors, and autonomic hyperreflexia. Goose bumps can also be caused by heroin withdrawal. A skin condition that mimics goose bumps in appearance is keratosis pilaris.

Goose bumps can occur only in mammals, since other animals do not have hair. The term "goose bumps" is therefore misleading: the bumps on the skin of a plucked goose technically do not qualify as piloerection. Birds do however have a similar reflex of raising their feathers in order to keep warm.

The Latin horrere is the root of words such as "horrific" or "horror"; it means "to stand on end" and refers to the standing hairs of goose bumps. In other languages, the "goose" may be replaced by other kinds of poultry. For instance, "hen" is used in French (la chair de poule), Spanish and Chinese (雞皮疙瘩).