Apter (1982, 1997) has pinpointed a number of major differences between the reversal theory approach to understanding aggressive and violent behaviour and the approach offered by other theories in the social sciences. First, reversal theory does not equate aggression and anger, unlike some other approaches (e.g. Isberg, 2000), but argues that aggression can occur both in the presence and in the absence of anger. Second, reversal theory is concerned with the immediate background of why aggression and violence occur, rather than taking the longer term perspective that other theories, dealing with evolution, genetics, subculture or upbringing, offer (e.g. Lorenz, 1966). Third, reversal theory can provide an understanding of a wide range of different types of aggressive and violent behaviour, where other theories have tended to concentrate on only one form of violent behaviour (e.g. aggression in children as a result of observation and imitation, Bandura, 1973). Fourth, reversal theory seeks multiple causes for aggressive and violent behaviour, where other theories have largely proposed single causes (e.g. drive theory, Dollard et al., 1939).