Jealousy is one of the most basic human experiences; it's even been observed in infants as young as five months old. Find out what jealousy is, what causes it, and why the green-eyed monster can be both destructive and productive. Dr. Maria Legerstee is Professor of Psychology at York University; Dr. Gordon Clanton is Sociology Professor at San Diego State University.

Weigh in: Tell us about your most intense experience with jealousy, and how it affected your life.