Here are five annoying things people do, and the scientific explanations for why we do them:

1. Constantly clearing your throat. It happens when the membrane of your upper respiratory tract gets inflamed. And it’s usually a sign of allergies. If it happens year round, you might be allergic to something in your house, like dust mites.

2. Over-sharing on Facebook. Researchers at Harvard used an MRI, and found that when people answered questions about themselves, the reward centers of their brain lit up. In other words, talking about yourself makes you feel good.

3. Biting your fingernails or fidgeting. Habits like that tend to be a sign of anxiety. And a recent study found you’re more likely to do it if you’re a perfectionist.

4. Loud, violent sneezing. It has to do with how strong your abdominal muscles are . . . how big your windpipe is . . . and how much air your lungs can hold. And some people also just naturally use more muscles when they sneeze.

5. Road rage. It has to do with how territorial you are. Some people subconsciously see their car as an extension of themselves.

In fact, a study at Colorado State recently found that people who put bumper stickers on their car are more likely to have road rage. Even if it’s something positive, like a sticker promoting world peace.