Is what the French mean by infidelity the same as what Australians mean? Or the same as the Japanese, or the Finns? Do different countries have different rules when it comes to extramarital sex?Delving into this taboo subject, Pamela Druckerman interviewed people all over the world, from retirees in South Florida to Muslim polygamists in Indonesia; from Hasidic Jews to the men who keep their mistresses in a concubine village outside Hong Kong. She talked to psychologists, sex researchers, marriage counsellors, and, most of all, cheaters and the people they've cheated on. Russian husbands and wives don't believe that beach-resort flings violate their marital vows. Japanese businessmen declare, "If you pay, it's not cheating". And South Africans may be the masters of creative accounting – pollsters there had to create separate categories for men who cheat and men who cheat only when drunk.With all this bending of the boundaries of marriage, knowing that by international standards Australians are extremely faithful may come as comforting news. Or maybe not.