When we experience relational hurts (whether through actions, words, or lack of encouragement), we often use phrases like "She broke my heart," or "He hurt my feelings," or it was like getting "punched in the gut." Researcher and neuroscientist Matthew D. Lieberman thought this was just too coincidental, so he set out to study the pain of social rejection. One of his studies involved putting people in a brain scanner while they played an Internet video game called Cyberball where three "people" (a subject and two computerized "players") toss a ball around to each other. The point of Cyberball is to make the research subject feel rejected. At first, all three players toss the ball to each other in turn. But at a certain point, the other two players cut the poor research participant out of the game. They toss the ball just to each other. Even though this is a silly game in a research study and has no bearing on real life, the research subjects were really hurt. They started feeling distress. They felt rejected. When they came out of the scanner, they kept talking to the researchers about how upset they were.

The most interesting part of the study is how their brains processed the social rejection. To the brain, social pain feels a lot like physical pain—a broken heart can feel like a broken leg, as Lieberman puts it. In his book Social, Lieberman writes, "Looking at the [brain scans], side by side, without knowing which was an analysis of physical pain and which was an analysis of social pain, you wouldn't have been able to tell the difference." In other words, "When human beings experience threats or damage to their social bonds, the brain responds in much the same way it responds to physical pain."