It’s goosebump season. As the nights draw in, temperatures drop, and horror movies slink onto our screens, you’ll feel the familiar prickle of raised hairs down your arms more often. But why do our bodies get goosebumps in the first place?
How goosebumps happen
Goosebumps are valuable tools for many animals. They keep mammals with thick fur warm by trapping air near their skin, or help make them look bigger when facing off against a rival. However, in humans, a wide range of emotions can also induce goosebumps. All of these different forms of goosebumps occur because of a patchwork of different cell types in our skin working together.
Goosebumps, or piloerection, to use their formal scientific name, happen when muscle cells in our skin called the arrector pili muscles (APM) contract. They do this when they receive signals from nearby nerve cells. APMs are connected to hair follicles in our skin. Contraction pulls on these follicles and causes the hairs to rise up. This movement causes our skin to form small goosebumps. In short, nerve cells instruct muscle cells to contract, causing our hair follicles to stand on end.
How your brain makes bumps
The nerve cells that kickstart the goosebump response are part of our autonomic nervous system—responsible for our fight-or-flight responses. These nerve signals shift how our body functions in response to our environment by releasing chemical messengers like epinephrine. If we encounter a predator, these signals alter the flow of blood and oxygen through our body in response. If the temperature rises, nerve cells direct our skin to start sweating and cool down the body.
Our nervous system doesn’t only direct responses to threats or changing temperatures, but also to other environmental stimuli. “We get goosebumps all the time,” says Jonathon McPhetres, an independent researcher who published several papers on piloerection while at Durham University.
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“We’re not really very good at monitoring our bodies, and we don’t notice them [goosebumps] a lot of times when they happen,” he adds. Scary movies or frightening stories also kickstart our autonomic nervous system and stimulate the release of epinephrine. To this part of your brain, being chased by a threat in real life and seeing a knife-wielding killer on screen aren’t all that different. Goosebump-linked sensations can also pop up alongside less threatening events, like beautiful music or deja vu. These responses are less well-understood, but we’ll explore that later.
Goosebumps are the same regardless of stimuli
Whether our bodies are responding to heat changes or emotional rollercoasters, the types of goosebumps our skin produces stay the same. “Your skin is really interesting and amazing. It’s not this stiff, still thing on your body that just protects your muscles. It’s moving and it’s changing all the time. It’s stretching, it’s squishing up, it’s getting thicker, getting thinner, and it is changing hairs around all to regulate your body temperature and to keep things in and out,” says McPhetres.
This dynamic wiring in our skin responds to information our senses perceive. Whether it’s a scary film or a temperature drop, says McPhetres, the message is the same: “This is something that could be damaging; something in the environment could change. You need to change how you operate.”
Goosebumps are more evident in animals with thicker body hair. However, McPhetres suggests that we shouldn’t view goosebumps in humans as a purely vestigial remnant from when we were hairier hominids.
Goosebumps are “associated with changes in your skin temperature,” says McPhetres. These changes aren’t major, but McPhetres says that goosebumps elicited by cold in one region of the body tend to occur across the entire body.
“If I put an ice pack on your thigh,” he says, “I’ve changed the temperature of your thigh and I can see different areas of your skin and your body change temperature a little bit as a response.” Goosebumps elicited by tickling, on the other hand, are a much more localized response.
Even though we’re in no real danger when we watch horror movies, they can still trigger our nervous system to create goosebumps as a fear response. Image: DepositPhotos
Goosebumps and “the chills”
Goosebumps aren’t the simplest thing to study, partly because they often occur without us noticing. Another challenge is that researchers often muddle together physiological responses, like goosebumps, with more subjective emotional reactions, like “cold chills.”
Separate from feelings of coldness during a fever, these chills, also called frissons, are tingling waves of pleasurable emotion, often elicited by art, such as powerful songs or symphonies. McPhetres notes that scientists associate chills with goosebumps, but while goosebumps are a physical reaction we can see and feel, chills are a more subjective experience.
McPhetres says that recordings of skin and the nervous system show that there are effectively no measurements that capture any differences at all during frissons. Roughly half of the time that people report feeling chills, they have no goosebumps in response. “The relation between chills and goosebumps is nothing,” he states.
Whether your goosebumps pop up alongside a soaring chorus, a freezing wind, or during the on-screen revenge of a cursed, bloodthirsty member of the undead, just know that they are your brain’s way of telling your body that something noteworthy is happening nearby. Our autonomic nervous system helped us survive prehistoric predators, and it will get us through the next Saw film, too.
This story is part of Popular Science’s Ask Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you’ve always wanted to know? Ask us.
The post Why you get goosebumps when you’re scared—or inspired appeared first on Popular Science.
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