What’s happening? Tiny little muscles at the base of the hairs pull them to attention, which raises the skin around the follicles into little bumps. “The doctor term for it is ‘pilomotor erection,’ which is a fancy term for making hair follicles stand up,” says Cain. But the condition’s nonclinical name is spot-on: Goose bumps make us resemble a defeathered fowl.
Why is your body doing it? In cold weather, puffed-up hair creates a barrier of insulation to keep heat inside. And though this natural response still works for animals that are covered in fur, with the loss of hair we’ve experienced over the course of evolution, it’s not really doing much for us anymore. This function can also be triggered by the fight-or-flight response we experience when we sense danger: The goal here is to make us look bigger and scarier (think of a porcupine with its needles in full effect or a cat whose fur is raised). But, once again, our modern-day baldness renders the effect less than impressive. Pleasure, sexual arousal, or even hearing a favorite song can net the same primitive response, though experts aren’t exactly sure why.
What should you do? Nothing: Goose bumps are a harmless evolutionary holdover. And, hey, if they feel good, like when you hear a haunting melody or your better half tickles your back, then just enjoy them.