Robert Agnew's general strain theory proposes that strain or stressors experienced on an individual level can lead to criminal or delinquent behavior. The theory identifies three main types of strain or negative stimuli that can cause this: the failure to achieve positively valued goals, the removal of positive stimuli, and the presence of negative stimuli. Agnew suggests that strain resulting from the disjunction between goals and expectations or between expectations and achievements is more likely to produce negative emotions like anger and frustration which could then justify criminal behavior for the individual. The theory also posits that repetitive strain may overload coping mechanisms and increase hostility over time.