This project supports the dissertation research of a cultural anthropologist studying the effects of growing up together on marital preferences. The project tests the "Westermarck hypothesis", that intimate interaction in early childhood ("cosocialization") leads to sexual indifference in adulthood. The study will take place in Morocco, where the custom of marriage with the father's brother's son can provide evidence to test the hypothesis. Psychological distances with regard to marital attraction will be estimated between interviewees, who will be adolescent males and females, and stimulus subjects, who will be a list of potential marriage partners. Cosocialized persons will be compared with non-cosocialized persons, holding constant the influences of other variables such as wealth, physical attractiveness and present social proximity. This research is important because understanding the nature of sexual attraction and childhood cosocialization helps to explain the function of the social life of families as well as shed light on inbreeding avoidance responses.