text: One site where gender is performed and socialized is in sport. Violent sports such as football are fundamental in naturalizing the equation of maleness with violence. Displays of strength and violence, through sports like football, help to naturalize elements of competition and hierarchy as inherently male behaviour. There is considerable evidence that males are hormonally predisposed to higher levels of aggression on average than females, due to the effects of testosterone. However, the violent and competitive nature of sports like football can only be an exclusively masculine domain if girls and women are excluded from participating altogether. The only means through which women are permitted to participate in football is as the passive spectator or cheerleader, although women do sometimes participate in other violent contact sports, such as boxing.
  When a child engages in behaviour or uses something that is more often associated with the opposite sex, this is referred to as crossing gender borders. When gender borders are crossed in adolescence, the children are policed by themselves. Conflicts and disagreements between boys are resolved by name-calling and teasing, physical aggression, and exclusion from the group. This brings confusion to the natural order of building their individualism, and stifles their creativity and freeplay, critical to developing lifelong skills in problem solving and decision making. Another notion which further confuses youth is "multiple masculinities" is introduced where variables such as social class, race, ethnicity, generation, and family status determines how these young men must perform their masculinity. Boys who fail to fit the social norm are forced to enter adolescence having experienced alienation from their social group and marginalized from the social order they strive to achieve in this stage of life.