Why Do We Get Goosebumps?

What happens in the skin when goosebumps form?

Goosebumps come from the contraction of tiny muscles at the base of hair follicles, which makes the hairs stand up and raises small bumps on the skin.^[7] Each of these muscles, called an arrector pili muscle, is a bundle of smooth muscle cells attached to a hair follicle.^[1] Sympathetic nerves supply the muscles, and when the nerve signals get stronger the muscles tighten and pull the hairs upright.^[1] As the muscles flex, the hair follicles rise a little, which is what turns smooth skin bumpy.^[3]

The reaction is involuntary.^[3] It is run by the sympathetic nervous system, which also handles the "fight or flight" response.^[1][3] Arrector pili are smooth muscles, so unlike skeletal muscles such as the biceps, they normally work outside conscious control.^[5] Medical terms for goosebumps include piloerection, horripilation and the pilomotor reflex.^[3]

Why does cold cause goosebumps?

Cold is the main physical trigger of goosebumps.^[3][4] Cold raises the activity of the sympathetic nerves, and the stronger nerve impulses make the arrector pili muscles contract.^[1] In an animal with a thick coat, the raised hairs trap air and create a layer of insulation.^[1] The reflex may save heat in two other ways as well: the contracting skin muscles generate heat, and the raised follicles close the skin's pores.^[3] Each of these effects may matter more for furry animals than for humans.^[3]

Sources do not fully agree on what goosebumps still do for people.^[1][6] In humans, goosebumps in the cold are considered a relic of the heat-saving response of furred ancestors.^[4] The authors of a 2020 study in the journal Cell wrote that piloerection has lost its role in temperature regulation in humans.^[1] A 2024 study challenged that view: it recorded 1198 goosebump episodes in eight participants and found that goosebumps responded to drops in skin temperature and came with a rise in skin temperature.^[6] Its author concluded that human goosebumps are not purely vestigial, meaning not just a leftover without a use, while noting that the results do not show goosebumps to be solely or directly responsible for the temperature changes.^[6]

Why do fear, music and strong emotions cause goosebumps?

The sympathetic nervous system receives input from many parts of the brain, including those involved in motivation, arousal and emotion.^[3] Danger, like cold, raises sympathetic nerve activity.^[1] Touch, temperature, sights and sounds travel by different routes, but all of them converge on the same sympathetic nerve fibres that supply the arrector pili muscles.^[6]

In self-report studies, the most common psychological triggers of goosebumps or chills are moving passages of music and scenes in movies, plays or books.^[4] Other typical triggers include great beauty in nature or art, seeing or reading about something heroic, nostalgic moments and physical contact with other people.^[4] In an experiment published in 2011, researchers played audio taken from music and films, recorded visible goosebumps with an optical system, and concluded that emotional goosebumps are a valuable indicator of being moved or touched.^[4]

More recent work questions how closely goosebumps follow feelings.^[7] In a paper published in 2024, a study of 80 participants found that observed goosebumps were not correlated with the emotions people reported.^[7] A second study in the same paper, with 27 participants, found that goosebumps persisted through repeated exposure to identical stimuli.^[7] The separate 2024 study of eight participants found that thermal, tactile and audio-visual stimuli were equally effective at causing goosebumps.^[6] Its author describes the reaction as a reflexive response to changes in the environment rather than a purely emotional one.^[6]

What do goosebumps do for animals with fur or feathers?

Charles Darwin, in a work published in 1872, noted that hardly any expressive movement is as general as the involuntary raising of hairs, feathers and similar skin structures.^[4] In animals, raising hairs, feathers or spines plays a role in temperature regulation, courtship and aggression.^[1]

Raised coat hair or feathers thicken the insulating layer of air around the body.^[4] A threatened animal puffs out its fur, which makes it look bigger and more dangerous.^[3] A porcupine does something similar when it puffs out its quills at a sign of danger.^[3] Birds may ruffle their feathers during courtship, to intimidate rivals, or to keep in heat when it is cold.^[6] Raised hair has also been observed in male chimpanzees during courtship.^[4]

What did the 2020 Cell study find about goosebumps and hair growth?

Humans do not seem to benefit much from goosebumps, which raises the question of why the reaction has been preserved through evolution.^[2] A team led by Ya-Chieh Hsu of Harvard University, working with Sung-Jan Lin of National Taiwan University, studied the question in mice and published the results in Cell in 2020.^[1][2]

Using electron microscopy, the researchers found that the sympathetic nerve does not only connect to the muscle: its fibres also wrap around the hair follicle stem cells like a ribbon and connect to them directly.^[2] The nerve regulates these stem cells with the chemical messenger norepinephrine, delivered through synapse-like structures.^[1] The muscle serves as structural support, because when the researchers removed it, the nerve retracted and its connection to the stem cells was lost.^[2]

At its normal low level of activity, the nerve kept the stem cells poised to regenerate.^[2] Under prolonged cold, the nerve was much more active, and the stem cells activated quickly and grew new hair.^[2] In the experiments, mice housed at 5°C showed the classic goosebumps reaction and produced new hairs in less than 2 weeks.^[1] The researchers describe this as a two-layer response: goosebumps give quick relief in the short term, and lasting cold tells the stem cells to grow a new hair coat.^[2]

The study also showed how the unit forms during development: the growing hair follicle releases a protein, Sonic Hedgehog, that directs the formation of the muscle, which then attracts the nerve.^[1][2] These findings were made in mice.^[2]