People need people. We have a fundamental motivation for positive and lasting relationships. This need to belong is deeply rooted in our evoluationary history and has consequences for modern psychological processes. I study what happens when relationships flourish and when they go awry. Some of my research has examined the pain of rejection. When people experience rejection, their body and mind process it as if it is actual pain. Giving people physical painkillers can reduce the pain of rejection. Other research has studied factors that can protect people against relationship conflict, such as commitment.