Goosebumps, also called the pilomotor reflex, are an involuntary response, meaning they happen without your thinking about it. Such diverse experiences as feeling chilled, being frightened, feeling strong emotions or hearing music can bring on the sensation of goosebumps. The same response can be observed in many animals as part of their "flight or fight" reaction to stress or danger.
What people call "goosebumps" is a temporary physiological response in which the tiny muscles attached to each hair contract, making a shallow depression around the hair. This causes the skin around each hair to stand out, resembling the skin of a plucked bird, hence the name "goosebumps." Exposure to cold temperatures also can cause hair to stand straight up. Although the pilomotor reflex serves a purpose in the animal world, goosebumps are of little use to humans.
Pilomotor Response in Animals
For animals with a thick coat of hair, the pilomotor response increases the layer of air between the hair and the skin, helping to conserve warmth. Many animals also demonstrate this response when they are being threatened, according to "Scientific American." A frightened cat's hair stands straight up, making it look larger and more fierce to its aggressor.
The physiological response of goosebumps is caused by your body's release of adrenaline. Adrenaline is a hormone regulated by the adrenal glands, which lie just above the kidneys. Besides causing goosebumps, adrenaline also can cause you to become teary or develop sweaty or trembling hands. Adrenaline increases blood pressure and makes the heart beat faster, and is behind the uneasy feeling of "butterflies" in the stomach.
Goosebumps are a common reaction when you are suddenly chilled by a change in air temperature. Strong emotions of love, grief, excitement, danger or patriotism also can bring on goosebumps. Often a person gets goosebumps years after the actual event, simply by recalling occasions when they felt such emotions.
Goosebumps and Music
Jaak Panksepp, a Bowling Green State neurobiologist, discovered that people who developed goosebumps from listening to music were more likely to experience them due to the recall of sad, rather than happy emotions, according to the Exploratorium website. He theorizes that goosebumps induced by music are connected to the human brain's chemical response to social loss. The cry of a lost child or relative might have triggered the pilomotor response in long-ago human ancestors, serving as a survival strategy by warning of danger and allowing tribal people to stay together.