On the other hand, gender is a social classification based on one’s identity, self-expression, behavior, and interaction with others. Sociologists regard gender as the identity of learning behavior and culture, so it is a social category. When people compare how men and women behave in different cultures, and how other genders exist in certain cultures and societies, gender is a social structure that becomes more apparent. In Western industrialized countries like the United States, people tend to look at masculinity and femininity by dichotomy, treating men and women as distinct and opposing people. However, other cultures have challenged this assumption, and the perceptions of masculinity and femininity are less obvious. For example, historically there was a class of people in the Navajo culture called berdaches, who were anatomically normal males but were defined as being considered to be the third gender between men and women. Berdaches marries other ordinary people (not Berdaches), although they are not considered homosexuals like Western culture today.