Goose bumps (or goose pimples) are created when tiny muscles at the base of each hair, known as arrector pili muscles, contract and pull the hair straight up. The reflex is started by the sympathetic nervous system, which is responsible for many fight-or-flight responses, and is known as piloerection or the pilomotor reflex, or, more traditionally, horripilation. It occurs in many mammals; a prominent example is porcupines, which raise their quills when threatened.
In humans, the formation of goose bumps is considered to be a vestigial reflex, i.e. a response that has lost its original function ; indeed, its original function in other apes is to raise the body’s hair to appear larger to scare off predators or to increase the amount of air trapped in the fur to make it more insulating. Now, humans’ goose bumps can extend to piloerection as a reaction to:
In the presence of flash-cold temperatures, for example being in a cold environment, and the skin being able to re-balance its surface temperature quickly. The stimulus of cold surroundings causes the tiny muscles attached to each hair follicle to contract. This contraction causes the hair strands to stand straight, the purpose of which is to aid in quicker drying via evaporation of water clinging to the hair which is moved upward and away from the skin.
When frightened or in awe. In an extremely stressful situation, the body can employ the “fight or flight” response. As the body prepares itself for either fighting or running, the sympathetic nervous system floods the blood with adrenaline (epinephrine), a hormone that speeds up heart rate, metabolism, and body temperature in the presence of extreme stress. Then the sympathetic nervous system also causes the piloerection reflex, which makes the muscles attached to the base of each hair follicle contract and force the hair up.
When moved by music. The pleasure experience is driven by the chemical dopamine, which produces physical effects known as “chills” that cause changes in heart rate, breathing, temperature and the skin’s electrical conductance. The responses correlate with the degree to which people rate the “pleasurability” of music. Dopamine release is greatest when listeners have a strong emotional response to music.
Medications and herbal supplements that affect body temperature and blood flow may cause piloerection too, for example the intake of yohimbine.
Piloerection is one of the signs of opioid withdrawal. The term “cold turkey” meaning abrupt withdrawal from a drug, may derive from the goose bumps that occur during abrupt withdrawal from opioids; this resembles the skin of a refrigerated plucked turkey.
Primate heritage hypothesis
People often experience goosebumps as a reaction to the sound of fingernails being dragged across a chalkboard. In 2006 American psychologist Randolph Blake, from Vanderbilt University in Nashville, Tennessee, conducted a study to find out why people react that way to the sound and discovered that the core sound causing the reaction was acoustically similar to that of a primate distress call.
An unknown proportion of people may also consciously initiate the sensation and physiological signs of piloerection. The phenomenon is discovered spontaneously, appearing to be innate, and is not known to be possible to learn or acquire.