We all know people on either side of the empathy spectrum—the friend who rushes over when you’re sad; the boss who keeps you late the night your kid is in the school play. Empathy stems from the actions of “mirror neurons” in your brain, which fire in response to other people’s actions, urging you to do the same thing. They are what make yawns contagious and cause you to subconsciously adopt a Southern accent while visiting New Orleans. These neurons also fire in response to emotions, which is why you feel sad when you watch a movie character cry, or wince when you see someone in pain. Since everyone is wired differently, emotional responses like empathy can vary widely from one person to the next.

MORE: How to Be Happy: Feeling Empathy