Travis Hirschi was an American criminologist known for his social-control perspective on juvenile delinquency and his self-control perspective on crime. Hirschi argued that delinquency can be explained by the absence of social bonds. According to Hirschi, social attachments (e.g., to parents, teachers, and peers), involvement in conventional activities, acceptance of social norms (such as the norm that criminal acts should be avoided), and recognition of the moral validity of law are most likely to prevent delinquency. Control theories assume that delinquent acts result when an individual's bond to society is weak or broken. Since these theories embrace two highly complex concepts, the bond of the individual to society, it is not surprising that they have at one time or another formed the basis of explanations of most forms of aberrant or unusual behavior. It is also not surprising that control theories have described the elements of the bond to society in many ways, and that they have focused on a variety of units as the point of control.