When a person notices a situation and defines it as requiring assistance, he or she must then decide if the responsibility to help falls on his or her shoulders. Thus, in the third step of the bystander decision-making process, diffusion of responsibility rather than social influence is the process underlying the bystander effect. Diffusion of responsibility refers to the fact that as the number of bystanders increases, the personal responsibility that an individual bystander feels decreases. As a consequence, so does his or her tendency to help. Thus, a bystander who is the only witness to an emergency will tend to conclude that he or she must bear the responsibility to help, and in such cases people typically do help. But bystanders diffuse responsibility to help when others are present. Diffusion of the responsibility is reduced, however, when a bystander believes that others are not in a position to help. For example, in one study, participants who believed that the only other witness to an emergency was in another building and could not intervene were much more likely to help a victim than were participants who believed that another witness was equally close to the victim.

Diffusion of the responsibility to help is increased when others who are viewed as more capable of helping (e.g., a doctor or police officer) are present. Research suggests that in emergency situations where a victim will suffer greatly if help is not forthcoming, bystanders relieve themselves of responsibility by asking “experts,” such as firefighters or paramedics, for assistance, thus indirectly helping. But when the costs of helping and not helping are both high, bystanders feel a strong conflict between the desire to act and the fear of helping. Bystanders often resolve this conflict by concluding that someone else will help (i.e., diffusing responsibility), thereby psychologically reducing the perceived cost of not helping the victim.

Normative social influence

A bystander’s decision regarding his or her personal responsibility to help may be affected by situational norms and expectations for behaviour. For example, in a library patrons are expected to be quiet and in a classroom students may speak up in a respectful and orderly way, but at a party people may be much less inhibited. When bystanders in an emergency situation assess their personal responsibility to act, social expectations for behaviour may influence their decision. Researchers have demonstrated the effect of situational expectations on helping behaviour by presenting people with an emergency in an area they have been told not to enter. Bystanders previously warned not to enter an area where an emergency was occurring were far less likely to help than bystanders who were told that they could enter the area. Thus, when an emergency occurs, the social context can be a powerful determinant of bystanders’ decision to intervene.