Diffusion of responsibility
Diffusion of responsibility is a sociopsychological phenomenon whereby a person is less likely to take responsibility for action or inaction when others are present. Considered a form of attribution, the individual assumes that others either are responsible for taking action or have already done so. The phenomenon tends to occur in groups of people above a certain critical size and when responsibility is not explicitly assigned. It rarely occurs when the person is alone and diffusion increases with groups of three or more.
Diffusion of responsibility occurs in large group settings and under both prosocial and antisocial conditions. In prosocial situations, individuals' willingness to intervene or assist someone in need is inhibited by the presence of other people. The individual is under the belief that other people present will or should intervene. Thus, the individual does not perceive it as his or her responsibility to take action. The Murder of Kitty Genovese is the classic case study for diffusion of responsibility in a prosocial situation. It has been demonstrated that the likelihood of a person offering help decreases as the number of observers present increases. This is known as the bystander effect. In addition, diffusion of responsibility is more likely to occur under conditions of anonymity. In prosocial situations, individuals are less likely to intervene when they do not know the victim personally. Instead, they believe that someone who has a relationship with the victim will assist. In antisocial situations, negative behaviors are more likely to be carried out when the person is in a group of similarly motivated individuals. The behavior is driven by the deindividuating effects of group membership and the diffusion of feelings of personal responsibility for the consequences. As part of this process, individuals become less self-aware and feel an increased sense of anonymity. As a result, they are less likely to feel responsible for any antisocial behavior performed by their group. Diffusion of responsibility is also a causal factor governing much crowd behavior, as well as risk-taking in groups.
Diffusion of responsibility can manifest itself:
- In a group of people who, through action or inaction, allow events to occur which they would never allow if they were alone. This is referred to as groupthink and groupshift.
- In a group of people working on a task who lose motivation, feel less responsibility for achievement of group goals, and hide their lack of effort in the group (social loafing).
- In hierarchical organizations, when subordinates claim to simply be following orders and supervisors claim that they merely issue directives and do not perform the actions under question. The difficulty of identifying the culpable party is often seen in trials regarding crimes against humanity.
Helping behavior 
Social psychological experiments have demonstrated that individuals' failure to assist others in emergencies is not due to apathy or indifference, but rather to the presence of other people. This is explained by both bystander effect and diffusion of responsibility. In 1968 and a series of experiments that followed, John Darley and Bibb Latané demonstrated that an individual's choice to help or intervene in an emergency situation depends on the number of bystanders. Group size significantly influenced the likelihood of helping behavior in a staged emergency: 85% of participants responded with intervention when alone, 62% of participants took action when with one other person, and only 31% did when there were four other bystanders. Other studies have replicated the phenomenon including reports from real emergency situations such as calling an ambulance for overdose patients and offering CPR after cardiac arrest.
In ambiguous situations, the individual's appraisal of the situation and subsequent action or inaction largely depends on the reactions of other people. Other bystanders' interpretation of an emergency situation influences perception of the incident and helping behavior. In one study, diffusion of responsibility does not occur if another bystander is perceived as being unable to help.
Group psychology can also influence behavior positively; in the event that one bystander takes responsibility for the situation and takes specific action, other bystanders are more likely to follow course. This is a positive example of the usually-pejorative herd mentality. Thus, the presence of bystanders affects individual helping behavior by processes of social influence and diffusion of responsibility.
Decision-making process 
- Noticing – realizing that there is a situation that may be an emergency
- Defining an emergency – interpreting cues as signals of an emergency
- Taking responsibility – personally assuming responsibility to act. People who have the necessary skills to help are more likely to do so. Single bystanders are more likely to help than groups.
- Planning a course of action – deciding how to help and what skills might be needed
- Taking action – initiating assistance. The cost of helping (e.g., danger to self) must not outweigh the rewards of helping, but a variety of complex and often altruistic factors influence this judgment.
- Observing smoke in a room (noticing)
- Recognizing that smoke is associated with fire, and therefore that people may be in danger (defining an emergency)
- Realizing that help is needed and that one has the capacity to assist (taking responsibility)
- Weighing responses (e.g., calling the fire department or attempting to put out the fire) and deciding on the most appropriate action for the situation (planning a course of action)
- Implementing the chosen action (taking action)
Risk-taking behavior 
In risk-taking literature, diffusion of responsibility occurs when individual members of a group feel less personal responsibility for potential failure in the pursuit of risky options than if acting alone. Such risky shift is a stable phenomenon that has been shown in experiments involving group discussion and consensus. For example, a study using risks and payoffs based on monetary gain and loss for problem-solving performance found a greater percentage of shift—hence, increased risk taking in group decision making.
Other research suggests that risky shifts can also be attributed to group polarization, majority rules, interpersonal comparisons, informational influence, and familiarization. Like diffusion of responsibility in emergency situations, the larger the size of the group during conditions of discussion and information exchange, the greater the risky shift.
Real-World Examples 
- In 1964, Kitty Genovese, a New York woman, was raped and stabbed to death near her apartment in the presence of several witnesses (reports vary wildly as to the actual number of witnesses). Reports of witnesses' inaction prompted research into possible explanations, which helped develop the concepts of diffusion of responsibility and the bystander effect.
The diffusion of responsibility for alleged war crimes during World War II was famously used as a legal defense by many of the Nazis being tried at Nuremberg. A similar defense was mounted by the defendants accused in the My Lai massacre.
See also 
- Collective responsibility
- Milgram experiment
- Design by committee
- Somebody Else's Problem
- Tragedy of the commons
- Nuremberg Defense
- Political gridlock under the presidential system
- Banality of evil
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