Zimbardo was consistent with Festinger "et al." in his suggestion that loss of individuality leads to a loss of control, causing affected persons to behave intensely and impulsively, having let go of internal restraints. However, he developed this model by specifying the "input variables" (situational factors) that lead to this loss of individuality, as well as the nature of behaviors that result (emotional, impulsive, and regressive). Zimbardo further developed existing deindividuation theory by suggesting these outcome behaviors are "self-reinforcing" and therefore difficult to cease. Moreover, Zimbardo did not restrict his application to group situations; he also applied deindividuation theory to "suicide, murder, and interpersonal hostility."