An estimated 40 percent of American marriages experience at least one episode of infidelity. Studies show more men than women cheat, but they often do it for the same reasons. While infidelity is a factor in many divorces, half of American marriages survive an extramarital affair. New social science and medical research is contributing to understanding the causes of infidelity. And it's helping therapists guide couples who seek to repair a damaged marriage. A discussion on what drives people to cheat and how infidelity can affect children and the whole family.