It happens when your sympathetic nervous system kicks, but can also be caused by stress, fear, or booze and drugs. If theyve got dilated pupils every time they see you, arent running screaming or obviously under the influence, they might be crushing.

How do you develop a crush?

Crushes come from your limbic brain, which is the part we share with animals. Its responsible for basic functions, like your heart beating and breathing in and out, but over the years humans developed a middle brain and a cortex on top, explains Dr Blumberg. Our limbic brain just wants dopamine.

What happens to your body when you have a crush?

When you have a crush on someone, the levels of dopamine in your body are elevated, causing feelings of both exhilaration and anxiety. See, you can thank dopamine for the way that your heart beats out of your chest and your hand trembles when you try to talk to her.