[MUSIC] Today we discuss a specific way in which norms can emerge. I say emerge because I want to stress that this process is a spontaneous one, not the outcome of a plan or a conscious decision. Social norms emerge by human action, not by human design. It is important to realize that often social norm developed from conventions, or descriptive norms. This happens when the convention lends itself to purposes it did not have when it was established. When a convention comes to signal group identity, status, or power, it also becomes normative. So when is specific behavior acquires such an important meaning for a group, failing to engage in it will be seen as offensive, as a rejection of the group and its values. A negative sanction will typically follow the transgression of what is now seen as required behavior. Think of tattoos, in gangs tattoos are a crucial identity marker. A five point crown, for example, is the symbol of the Latin Kings gang, which is one of the biggest Hispanic gangs in the US based out of Chicago. It is a critical signal of membership. Here you see how a conventional sign has acquired a strong normative value. A gang member should have a specific tattoo to signal his belonging and loyalty to the group. Another example is manners. Ways of greeting people often acquire meaning that goes well beyond their conventional nature. We can imagine that greeting people we know became quite habitual. Eventually, failing to greet an acquaintance would signal indifference, displeasure, even hostility. It acquired a negative meaning because we have come to feel entitled to a courteous greeting. We are in the realm of normative expectations. Similarly, table manners and other rules of etiquette developed to become a sign of aristocratic upbringing and refinement, and were used to exclude those who did not belong to the ruling class. A 13th century peasant would be excused if he drank from the dish or blew his nose in the table cloth. No nobleman was allowed to such lack of manners. Good manners thus became a signal of status and power. A member of the ruling class was identified as such, through his courteous manners. Not respecting the rules of etiquette was met with contempt, as a threat to the established class boundaries. Foot binding in China is another example of a convention that devolved into social norm. There are many stories about its origin, but in time it spread to all but the lowest classes in the population, becoming a sign of gentility and modesty, as well as an essential condition for marriageability. Not binding one's daughter feet came to signal disregard for tradition and custom, and such family would be disparaged. Foot binding had become a social norm. In all these examples, conventional activities came to acquire an important social signaling function. Because of that, both empirical and normative expectation developed, and lent support to these practices.