In terms of explaining reasons for which individuals join terrorist groups, motivational theories such as need for power and need for affiliation intimacy are suggested. Festinger (1954) explained that people often join groups in order to compare their own beliefs and attitudes. Joining a terrorist group could be a method to remedy individual uncertainty. Taylor and Louis (2004) explained that individuals strive for meaningful behavior. This can also be used to explain why terrorists look for such radical beliefs and demonstrations. Studies on children in northern Ireland by Field (1979) have shown that exposure to violence can lead to terrorist behavior later on. Implicating the effect of developing acceptable norms in groups. However this view has also been criticized (Taylor, 1998). Other theories suggest that goal frustration can result in aggression (Dollard, Doob. Miller, mower, and Sears, 1939) and that aggression can lead to frustration (Borum, 2004).