We've all been there: watching a movie when suddenly your eyes well up, or hearing a song that sends tears streaming down your face. Maybe it's a wedding, a funeral, or just an overwhelming Tuesday.

Prologue -- The structure of this book -- Six paradigms -- 1. Introduction -- Some premises -- Some history -- Evolution and modification of behavior -- Evolution of ontogeny in the human animal -- ...

Who hasn't had the experience of asking someone whether anything is wrong—for it's blatantly obvious from their expression or tone of voice that they're upset—only to have them respond, "No, I'm fine" ...