When Captain Cook asked the chiefs in Tahiti why they always ate (26)apart and alone, they replied, "Because it is right." If we ask Americans why they eat with knives and forks, or why their men wear pants (27)instead of skirts or why they may be married to only one person at a time, we are likely to get (28)similar and very uninformative answers: "Because it's right." "Because that's the way it's done." "Because it's the(29) custom." Or even "I don't know." The reason for these and countless other patterns of social behavior is that they are(30) controlled by social norms – shared rules or guidelines which prescribe the behavior that is appropriate in a given situation. Norms (31)define how people "ought to" behave under particular circumstances in a particular society. We conform (遵守) to norms so readily that we are hardly aware they (32)exist. In fact we are much more likely to notice (33)departures from norms than conformity to them. You would not be surprised if a stranger tried to shake hands when you were introduced, but you might be a little (34)startled if they bowed, started to stroke you or kissed you on both (35)cheeks. Yet each of these other forms of greeting is appropriate in other parts of the world. When we visit another society whose norms are different, we quickly become aware that things we do this way, they do that way.