 And this was a study we were really excited about. We didn't particularly expect it to get a lot of attention, but many people came calling, and one minute I'm lecturing in introductory social psychology about the psychology of love, and the next minute I'm in a studio across campus doing an interview for the CBS Evening News. So when we're alone, we experience physical pain, and that's a cue to say it's time to get things back on track.