Why do we get goosebumps?
For grown-ups: the science
Goosebumps happen when tiny muscles pull your little hairs upright.
Goosebumps, or piloerection, occur when arrector pili muscles at the base of hair follicles contract and pull hairs upright. The sympathetic nervous system can trigger this reflex in cold temperatures or during strong emotions such as fear or awe. In furry ancestors, raised hair could trap insulating air or make the animal appear larger; in modern humans, sparse body hair means the response has no significant warming or protective effect.
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Transcript
Look at the tiny hairs on your arm. Why do little bumps sometimes pop up around them?
Each little hair sits in a tiny pocket in your skin with a tiny muscle at its base. When that muscle squeezes, it pulls the hair upright.
Cold, or a strong feeling like awe, can send messages through your nerves to those tiny muscles. That is why bumps can pop up when you feel chilly or amazed.
Long ago, our furry ancestors' thicker fur could hold extra air when it stood up. Our sparse body hair means goosebumps do not warm us much now.
So, goosebumps are tiny muscles lifting your hairs. They are an old body response that people still have today.