Science of Everything: Goosebumps

You’re watching a scary movie. All of a sudden, you notice the eerie, tense silence that can only precede a jump scare. Every muscle is taut, you cover your eyes (to varying degrees of success), and then you feel the hairs on the back of your neck and all over your body raise in anticipation.

R.L. Stein, you’ve done it again.

Piloerection, more commonly known as goosebumps, is a phenomenon that accompanies intense emotions or acts as a response to various stimuli. Named for its similar appearance to the skin of a plucked goose (gross), goosebumps may feel unnecessary, but they’re actually rooted in evolution.

“Goosebumps is a physiological response to our environment via our skin. And actually, this is a response that all mammals have,” explained Dr. Eric Gorscak, associate professor of anatomy at Midwestern University.

Because we experience goosebumps in a variety of situations, their function is just as varied. Take, for instance, the goosebumps that you get when you feel a chilly breeze. Our much hairier ancestors got goosebumps as a means of trapping air between the hair follicles, which created a barrier against the cold. 

“It’s good insulation to keep you warm in a cold environment,” Dr. Gorscak said. “Now, the problem is we’re humans. We don’t have as much hair, so when our hairs stick up, it’s not really capturing anything. So this is what’s known as a vestigial reflex from a more hairy ancestry.”

Vestigial reflexes refer to anatomical functions that our bodies still perform, despite having evolved beyond the need for them. While we no longer have enough hair to be kept warm by goosebumps, our body is still wired to perform the response. Goosebumps caused by fear served a very different function but also evolved into a vestigial reflex. To describe this, Dr. Gorscak points to the concept of a “scaredy cat.”

“If you think of a cat getting scared, it puffs up. It has all the hairs sticking out, staying erect, and makes it look bigger to at least try to scare off what’s scaring it,” Dr. Gorscak said. These goosebumps are supposed to help us ward off predators, but our evolved lack of hair once again neutralizes the effectiveness of this response. Unless, that is, our horror movie villains have a fear of plucked poultry.

Cold and fear are probably the first two things you think of when you think of goosebumps. But if you’ve ever heard a moving symphony or felt your emotions swell at the climax of a play, you know that goosebumps can come as a result of positive stimuli, too.

“When you feel fear, you become more alert, [and] any kind of art or music or what have you is arousing you and causing you to feel more alert, and so it’s creating that same response,” Dr. Gorscak said. Our nervous system feels the intense emotions brought on by a piece of art and uses a response from a feeling it deems to be similar. This means you may be just as likely to experience goosebumps from horrifying phantom movie effects as you are from a beautiful melody in The Phantom of the Opera.

Hairier mammals may still reap the survival benefits of goosebumps, but humans have long since evolved beyond the need for them. If anything, seeing goosebumps on your friend’s arm during a scary movie marathon might prove they’re just as scared as you are, but you’ll have to peek out from behind your fingers to see it.