The term bystander effect refers to the phenomenon in which the greater the number of people present, the less likely people are to help a person in distress. When an emergency situation occurs, observers are more likely to take action if there are few or no other witnesses.
In a series of classic studies, researchers Bibb Latane and John Darley (1) found that the amount of time it takes the participant to take action and seek help varies depending on how many other observers are in the room. In one experiment, subjects were placed in one of three treatment conditions: alone in a room, with two other participants or with two confederates who pretended to be normal participants.
As the participants sat filling out questionnaires, smoke began to fill the room. When participants were alone, 75% reported the smoke to the experimenters. In contrast, just 38% of participants in a room with two other people reported the smoke. In the final group, the two confederates in the experiment noted the smoke and then ignored it, which resulted in only 10% of the participants reporting the smoke.
Read More: What is the Bystander Effect?