Some factors:
People are more likely to lie or cheat if others are lying or cheating, or if a member of another social group (such as a student wearing a sweatshirt from a rival university) visibly flouts the rules. They are more likely to lie and cheat if they are in a foreign country rather than at home. Or if they are using digital rather than real money. Or even if they are knowingly wearing fake rather than real Gucci sunglasses.
The Dish 