Situational explanations for institutional aggression, within the context of prisons, focus on aggression stemming from factors within the social situation. One example is the deprivation model, which suggests that the aggression shown by many prison inmates is caused by the deprivations they experience on a daily basis. Sykes (1958) outlined five deprivations that he believed were caused by the indignities and degradations suffered by inmates: deprivation of liberty; deprivation of autonomy; deprivation of goods and services; deprivation of heterosexual relationships; and deprivation of security.