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The Bystander Effect

Updated: Jul 25, 2021

The bystander effect is a simple concept: when in an emergency situation, observers are more likely to take action if there are few or no other witnesses [2]

Author: Kaz Shuji

A homeless man passes out on the street while people walk by.  What is happening here and why does it seem to happen often? [1]

We are less likely to offer help to someone when there are other people present [2]. Social psychologists Bibb Latané and John Darley called this phenomenon the bystander effect [3]. The concept stemmed from the infamous murder of Kitty Genovese in 1964, where the 28-year-old woman was sexually assaulted and stabbed to death outside her apartment with dozens of witnesses present [4]. Shockingly, it was reported that not a single person intervened or called the police until after the attacker fled the scene [4]. Although the specifics of the incident have been highly debated, one thing is for certain: there was a lack of action taken by the witnesses to stop the attacker or save Kitty’s life [4]. We naturally ask ourselves, why? Why didn’t anyone do anything to stop the attacker? If you witnessed an emergency happening right before your eyes, you would take action to help in some way, right? While this may be what we think we would do, psychologists believe that, in reality, whether or not we help at the moment depends on the number of other witnesses present [2].

The bystander effect is a simple concept: when in an emergency situation, observers are more likely to take action if there are few or no other witnesses [2]. In other words, the greater the number of bystanders, the less likely individuals will take action [2]. Bibb Latané and Judith Rodin conducted an experiment in 1969 to demonstrate this effect [2]. They staged a scene around a woman in distress, and subjects were either alone or paired with strangers [2]. They found that 70% of subjects would help a woman in distress when they were the only witness, while only 40% of subjects offered assistance when other strangers were around [2]. Naturally, we wonder why more witnesses inhibit individuals from offering help. Latané and Darley believed that this is attributed to two main factors. The first is a diffusion of responsibility, where the more bystanders there are, the less personal responsibility individuals will feel to take action [3]. The second is social influence, where individuals observe the behaviour of those around them to determine how to act [3].

When delving deeper into Latané and Darley’s ideas, they define an emergency situation as a threat or harm that requires immediate action [5]. They cannot be expected and are unusual or rare situations in everyday life, and the type of action required in an emergency differs from situation to situation [5]. To simulate an emergency situation with these criteria in mind, Latané and Darley (1968) placed students in a room either alone or in groups to complete a questionnaire. While the students were working, the room was purposely filled with smoke [2]. In such emergencies, Latané and Darley believed that bystanders go through a series of five cognitive and behavioural processes [6].

First, bystanders will notice and interpret the emergency situation [6]. In the experiment with students, Latané and Darley found that students working alone noticed the fire almost immediately (within 5 seconds), while students working in groups took longer to notice (up to 20 seconds) [6]. Furthermore, they noticed that students interpreted the emergency based on the interpretation of their peers, which follows the principles of social influence [6]. In essence, students alone in the room have no other students to base their behaviour on, resulting in a greater likelihood of reporting the smoke due to their own intuition and decision [6]. On the contrary, students working in groups were likely to form their interpretations and behaviours based on other students [6]. This resulted in ignoring emergency situations simply because other students were not reacting to it and this becomes interpreted as the norm [6]. This is an example of pluralistic ignorance, in which individuals of a group reject a norm, but go along with it anyway because they assume, incorrectly, that most others accept it [6]. Therefore, people may experience an emergency situation and think to themselves that it is an emergency, but because they observe that the people around them are not reacting to it, they falsely assume that it is not serious and incorrectly interpret it as a non-emergency situation [6]. When there are more people who think the same way, the greater the bystander effect becomes [6].

Once an emergency situation has been noticed and interpreted, Latané and Darley determined that the degree of responsibility a bystander feels is dependent on whether the situation or person is worth helping according to the bystander’s opinion, the competence of the bystanders, and the relationship between the bystander and the situation or person needing help [6]. Of course, the greater the sense of responsibility one feels and the closer the bystander feels personally to the situation or person, the less likely the bystander effect occurs and the more willing the bystanders will be to help [6].

Following this, Latané and Darley believed that there are essentially two forms of assistance that bystanders can partake in: direct intervention, where bystanders will directly help the situation or person; or detour intervention, where bystanders will report the emergency to the authorities [6].

Once bystanders have noticed, interpreted, determined their degree of responsibility, and decided on the form of assistance, bystanders will implement their action of choice, which essentially results in either performing the assistance chosen or ignoring the situation and creating the bystander effect, which is amplified by the number of bystanders in the vicinity [6].

Although Latané and Darley’s work have been the foundation of the bystander effect and the further understanding of social psychology, recent research has been focused on real-world situations that have been shown to refute Latané and Darley’s hypotheses. For instance, Philpot et al. (2019) examined real-life surveillance videos from various countries around the world to determine whether actual public victims will be helped by others in emergencies. They found that intervention was frequent despite large numbers of bystanders [7]. They concluded that increased bystander presence can increase the likelihood that someone would intervene, even if the chances of each individual bystander responding becomes reduced [7]. Further research on real-life events such as these, rather than experimentally derived situations, can be more useful in understanding the bystander effect.

In summary, the bystander effect suggests that the likelihood of intervening in an emergency situation is inversely related to the number of bystanders present [6]. Thus, the more witnesses there are, the less likely the emergency situation will be dealt with immediately [6]. This is mostly due to diffused responsibility and pluralistic ignorance, along with a series of cognitive processes that occur in each bystander’s mind during the situation [6].

So, what can we do to overcome and prevent the bystander effect? Many psychologists believe that simply understanding and being aware of the bystander effect may be all that is needed to prevent it from occurring [2,3]. Once we become aware of the consequences of the bystander effect as individuals, we can take action in emergencies to prevent others from creating the bystander effect [2,3]. It is natural for people to be stressed or go into a state of shock when witnessing extreme situations, resulting in the bystander effect simply due to fear [3]. If you can process the situation calmly, a recommended tactic is to take the lead, single out certain people in the crowd, and ask them for help [2,3]. Such a tactic can prevent excessive bystander effect by providing tasks for various individuals to accomplish [3]. Your understanding of the bystander effect and how to deal with it as a group in emergency situations can go a long way and may even result in collectively saving someone’s life.


Alison MacPhee. Jasmine Kokkat, Rhea Verma


Web design by Majd Al-Aarg

Additional Credits

Cover photo provided by LuAnn Hunt on Unsplash


  1. Olsson A. Homeless man [Internet image]. 2011 [cited 2020 Nov 16]. Available from:

  2. Cherry, K. [Internet]. New York (NY): Verywell Mind. How psychology explains the bystander effect; 2020 [cited 2020 Nov 16]. Available:

  3. History [Internet]. New York (NY): A&E Television Networks. Kitty Genovese; 2018 [cited 2020 Nov 16]. Available:

  4. Psychology Today [Internet]. New York (NY): Psychology Today. Bystander effect [cited 2020 Nov 16]. Available:

  5. Babson College Faculty Web Server [Internet]. Wellesley (MA): Babson College. Latane and Darley: Bystander apathy [cited 2020 Nov 16]. Available:

  6. The Albert Team [Internet]. Chicago (IL): Who were Latane and Darley? AP Psychology bystander effect review; 2020 [cited 2020 Nov 16]. Available:

  7. Philpot R, Liebst L, Levine M, Bernasco W, Lindegaard M. Would I be helped? Cross-national CCTV footage shows that intervention is the norm in public conflicts. American Psychologist Association [Internet]. 2020 [cited 2020 Nov 16]; 75(1):66-75. Available from: doi:10.1037/amp0000469

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