Most violent behavior is learned behavior. Early exposure to violence in the family may involve witnessing either violence or physical abuse. Research suggests that these forms of exposure to violence during childhood increase the risk of violent behavior during adolescence by as much as 40 percent. Even if violence is not modeled in the home, research suggests that the absence of effective social bonds and controls, together with a failure of parents to teach (and children to internalize) conventional norms and values, puts children at risk of later violence. Some neighborhoods also provide opportunities for learning and engaging in violence. The presence of gangs and illegal markets, particularly drug distribution networks, not only provides high levels of exposure to violence, but violent role models and positive rewards for serious violent activity. Although patterns of behavior learned in early childhood carry over into the school environment, the school also has its own potential for generating conflict, frustration, and violent responses to these situations. There is evidence that school dropouts, drug dealers, and those with a prior record of violent behavior are more likely to own a gun than are other adolescents. Research findings suggest that growing up in poor, minority families and disorganized neighborhoods has two major effects directly related to violent behavior. First, when it comes time to make the transition into adulthood, there are limited opportunities for employment, which reduces the chances of marriage. Secondly, there is evidence that growing up in poor, disorganized neighborhoods inhibits the normal course of adolescent development.