Bystander effect

The bystander effect, or bystander apathy, is a social psychological phenomenon that refers to cases in which individuals do not offer any means of help to a victim when other people are present. The probability of help is inversely related to the number of bystanders. In other words, the greater the number of bystanders, the less likely it is that any one of them will help. Several variables help to explain why the bystander effect occurs. These variables include: ambiguity, cohesiveness and diffusion of responsibility.

The bystander effect was first demonstrated in the laboratory by John Darley and Bibb Latané in 1968 after they became interested in the topic following the murder of Kitty Genovese in 1964. These researchers launched a series of experiments that resulted in one of the strongest and most replicable effects in social psychology. In a typical experiment, the participant is either alone or among a group of other participants or confederates. An emergency situation is staged and researchers measure how long it takes the participants to intervene, if they intervene. These experiments have found that the presence of others inhibits helping, often by a large margin. For example, Bibb Latané and Judith Rodin (1969) staged an experiment around a woman in distress. 70 percent of the people alone called out or went to help the woman after they believed she had fallen and was hurt, but when there were other people in the room only 40 percent offered help.

Latané and Darley performed three experiments to test bystander behavior in non-emergency situations Their results indicated that the way in which the subjects were asked for help mattered. In one condition, subjects asked a bystander for his or her name. More people gave an answer when the students gave a name first. In another condition, the students asked bystanders for a dime. When the student gave an explanation (i.e."My wallet has been stolen"), the percentage of people giving assistance was higher (72%) than when the student just asked for a dime (34%). Essentially, when asking for assistance, the more information given to a bystander, the more likely they will help. Additional research by Faul, Mark, et al., using data collected by EMS officials when responding to an emergency, indicated that the response of bystanders was correlated with the health severity of the situation.

...
Wikipedia