smoke filled experiment

Bystander Effect In Psychology

Udochi Emeghara

Research Assistant at Harvard University

B.A., Neuroscience, Harvard University

Udochi Emeghara is a research assistant at the Harvard University Stress and Development Lab.

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Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

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Take-home Messages

The bystander effect is a social psychological phenomenon where individuals are less likely to help a victim when others are present. The greater the number of bystanders, the less likely any one of them is to help.
Factors include diffusion of responsibility and the need to behave in correct and socially acceptable ways.
The most frequently cited real-life example of the bystander effect regards a young woman called Kitty Genovese , who was murdered in Queens, New York, in 1964 while several of her neighbors looked on. No one intervened until it was too late.
Notice the event (or in a hurry and not notice).
Interpret the situation as an emergency (or assume that as others are not acting, it is not an emergency).
Assume responsibility (or assume that others will do this).
Know what to do (or not have the skills necessary to help).
Decide to help (or worry about danger, legislation, embarrassment, etc.).
Latané and Darley (1970) identified three different psychological processes that might prevent a bystander from helping a person in distress: (i) diffusion of responsibility; (ii) evaluation apprehension (fear of being publically judged); and (iii) pluralistic ignorance (the tendency to rely on the overt reactions of others when defining an ambiguous situation).
Diffusion of responsibility refers to the tendency to subjectively divide personal responsibility to help by the number of bystanders present. Bystanders are less likely to intervene in emergency situations as the size of the group increases, and they feel less personal responsibility.

Bystander effect concept. Wooden figurines and in the middle lies red one.

What is the bystander effect?

The term bystander effect refers to the tendency for people to be inactive in high-danger situations due to the presence of other bystanders (Darley & Latané, 1968; Latané & Darley, 1968, 1970; Latané & Nida, 1981).

Thus, people tend to help more when alone than in a group.

The implications of this theory have been widely studied by a variety of researchers, but initial interest in this phenomenon arose after the brutal murder of Catherine “Kitty” Genovese in 1964.

Through a series of experiments beginning in the 1960s and 1970s, the bystander effect phenomenon has become more widely understood.

Kitty Genovese

On the morning of March 13, 1964, Kitty Genovese returned to her apartment complex, at 3 am, after finishing her shift at a local bar.

After parking her car in a lot adjacent to her apartment building, she began walking a short distance to the entrance, which was located at the back of the building.

As she walked, she noticed a figure at the far end of the lot. She shifted directions and headed towards a different street, but the man followed and seized her.

As she yelled, neighbors from the apartment building went to the window and watched as he stabbed her. A man from the apartment building yelled down, “Let that girl alone!” (New York Times, 1964).

Following this, the assailant appeared to have left, but once the lights from the apartments turned off, the perpetrator returned and stabbed Kitty Genovese again. Once again, the lights came on, and the windows opened, driving the assaulter away from the scene.

Unfortunately, the assailant returned and stabbed Catherine Genovese for the final time. The first call to the police came in at 3:50 am, and the police arrived in two minutes.

When the neighbors were asked why they did not intervene or call the police earlier, some answers were “I didn”t want to get involved”; “Frankly, we were afraid”; “I was tired. I went back to bed.” (New York Times, 1964).

After this initial report, the case was launched to nationwide attention, with various leaders commenting on the apparent “moral decay” of the country.

In response to these claims, Darley and Latané set out to find an alternative explanation.

Decision Model of Helping

Latané & Darley (1970) formulated a five-stage model to explain why bystanders in emergencies sometimes do and sometimes do not offer help.

At each stage in the model, the answer ‘No’ results in no help being given, while the answer ‘yes’ leads the individual closer to offering help.

However, they argued that helping responses may be inhibited at any stage of the process. For example, the bystander may not notice the situation or the situation may be ambiguous and not readily interpretable as an emergency.

The five stages are:

The bystander must notice that something is amiss.
The bystander must define that situation as an emergency.
The bystander must assess how personally responsible they feel.
The bystander must decide how best to offer assistance.
The bystander must act on that decision.

Classic model by Latané and Darley (1970)

Figure 1. Decision Model of Helping by Latané and Darley (1970).

Why does the bystander effect occur?

Latane´ and Darley (1970) identified three different psychological processes that might interfere with the completion of this sequence.

Diffusion of Responsibility

The first process is a diffusion of responsibility, which refers to the tendency to subjectively divide the personal responsibility to help by the number of bystanders.

Diffusion of responsibility occurs when a duty or task is shared between a group of people instead of only one person.

Whenever there is an emergency situation in which more than one person is present, there is a diffusion of responsibility. There are three ideas that categorize this phenomenon:

The moral obligation to help does not fall only on one person but the whole group that is witnessing the emergency.
The blame for not helping can be shared instead of resting on only one person.
The belief that another bystander in the group will offer help.

Darley and Latané (1968) tested this hypothesis by engineering an emergency situation and measuring how long it took for participants to get help.

College students were ushered into a solitary room under the impression that a conversation centered around learning in a “high-stress, high urban environment” would ensue.

This discussion occurred with “other participants” that were in their own room as well (the other participants were just records playing). Each participant would speak one at a time into a microphone.

After a round of discussion, one of the participants would have a “seizure” in the middle of the discussion; the amount of time that it took the college student to obtain help from the research assistant that was outside of the room was measured. If the student did not get help after six minutes, the experiment was cut off.

Darley and Latané (1968) believed that the more “people” there were in the discussion, the longer it would take subjects to get help.

The results were in line with that hypothesis. The smaller the group, the more likely the “victim” was to receive timely help.

Still, those who did not get help showed signs of nervousness and concern for the victim. The researchers believed that the signs of nervousness highlight that the college student participants were most likely still deciding the best course of action; this contrasts with the leaders of the time who believed inaction was due to indifference.

This experiment showcased the effect of diffusion of responsibility on the bystander effect.

Evaluation Apprehension

The second process is evaluation apprehension, which refers to the fear of being judged by others when acting publicly.

People may also experience evaluation apprehension and fear of losing face in front of other bystanders.

Individuals may feel afraid of being superseded by a superior helper, offering unwanted assistance, or facing the legal consequences of offering inferior and possibly dangerous assistance.

Individuals may decide not to intervene in critical situations if they are afraid of being superseded by a superior helper, offering unwanted assistance, or facing the legal consequences of offering inferior and possibly dangerous assistance.

Pluralistic Ignorance

The third process is pluralistic ignorance, which results from the tendency to rely on the overt reactions of others when defining an ambiguous situation.

Pluralistic ignorance occurs when a person disagrees with a certain type of thinking but believes that everyone else adheres to it and, as a result, follows that line of thinking even though no one believes it.

Deborah A. Prentice cites an example of this. Despite being in a difficult class, students may not raise their hands in response to the lecturer asking for questions.

This is often due to the belief that everyone else understands the material, so for fear of looking inadequate, no one asks clarifying questions.

It is this type of thinking that explains the effect of pluralistic ignorance on the bystander effect. The overarching idea is uncertainty and perception. What separates pluralistic ignorance is the ambiguousness that can define a situation.

If the situation is clear (for the classroom example: someone stating they do not understand), pluralistic ignorance would not apply (since the person knows that someone else agrees with their thinking).

It is the ambiguity and uncertainty which leads to incorrect perceptions that categorize pluralistic ignorance.

Rendsvig (2014) proposes an eleven-step process to explain this phenomenon.

These steps follow the perspective of a bystander (who will be called Bystander A) amidst a group of other bystanders in an emergency situation.

Bystander A is present in a specific place. Nothing has happened.
A situation occurs that is ambiguous in nature (it is not certain what has occurred or what the ramifications of the event are), and Bystander A notices it.
Bystander A believes that this is an emergency situation but is unaware of how the rest of the bystanders perceive the situation.
A course of action is taken. This could be a few things like charging into the situation or calling the police, but in pluralistic ignorance, Bystander A chooses to understand more about the situation by looking around and taking in the reactions of others.
As observation takes place, Bystander A is not aware that the other bystanders may be doing the same thing. Thus, when surveying others’ reactions, Bystander A “misperceives” the other bystanders” observation of the situation as purposeful inaction.
As Bystander A notes the reaction of the others, Bystander A puts the reaction of the other bystanders in context.
Bystander A then believes that the inaction of others is due to their belief that an emergency situation is not occurring.
Thus, Bystander A believes that there is an accident but also believes that others do not perceive the situation as an emergency. Bystander A then changes their initial belief.
Bystander A now believes that there is no emergency.
Bystander A has another opportunity to help.
Bystander A chooses not to help because of the belief that there is no emergency.

Pluralistic ignorance operates under the assumption that all the other bystanders are also going through these eleven steps.

Thus, they all choose not to help due to the misperception of others’ reactions to the same situation.

Other Explanations

While these three are the most widely known explanations, there are other theories that could also play a role. One example is a confusion of responsibility.

Confusion of responsibility occurs when a bystander fears that helping could lead others to believe that they are the perpetrator. This fear can cause people to not act in dire situations.

Another example is priming. Priming occurs when a person is given cues that will influence future actions. For example, if a person is given a list of words that are associated with home decor and furniture and then is asked to give a five-letter word, answers like chair or table would be more likely than pasta.

In social situations, Garcia et al. found that simply thinking of being in a group could lead to lower rates of helping in emergency situations. This occurs because groups are often associated with “being lost in a crowd, being deindividuated, and having a lowered sense of personal accountability” (Garcia et al., 2002, p. 845).

Thus, the authors argue that the way a person was primed could also influence their ability to help. These alternate theories highlight the fact that the bystander effect is a complex phenomenon that encompasses a variety of ideologies.

Bystander Experiments

In one of the first experiments of this type, Latané & Darley (1968) asked participants to sit on their own in a room and complete a questionnaire on the pressures of urban life.

Smoke (actually steam) began pouring into the room through a small wall vent. Within two minutes, 50 percent had taken action, and 75 percent had acted within six minutes when the experiment ended.

In groups of three participants, 62 percent carried on working for the entire duration of the experiment.

In interviews afterward, participants reported feeling hesitant about showing anxiety, so they looked to others for signs of anxiety. But since everyone was trying to appear calm, these signs were not evident, and therefore they believed that they must have misinterpreted the situation and redefined it as ‘safe.’

This is a clear example of pluralistic ignorance, which can affect the answer at step 2 of the Latané and Darley decision model above.

Genuine ambiguity can also affect the decision-making process. Shotland and Straw (1976) conducted an interesting experiment that illustrated this.

They hypothesized that people would be less willing to intervene in a situation of domestic violence (where a relationship exists between the two people) than in a situation involving violence involving two strangers. Male participants were shown a staged fight between a man and a woman.

In one condition, the woman screamed, ‘I don’t even know you,’ while in another, she screamed, ‘I don’t even know why I married you.’

Three times as many men intervened in the first condition as in the second condition. Such findings again provide support for the decision model in terms of the decisions made at step 3 in the process.

People are less likely to intervene if they believe that the incident does not require their personal responsibility.

Critical Evaluation

While the bystander effect has become a cemented theory in social psychology, the original account of the murder of Catherine Genovese has been called into question. By casting doubt on the original case, the implications of the Darley and Latané research are also questioned.

Manning et al. (2007) did this through their article “The Kitty Genovese murder and the social psychology of helping, The parable of the 38 witnesses”. By examining the court documents and legal proceedings from the case, the authors found three points that deviate from the traditional story told.

While it was originally claimed that thirty-eight people witnessed this crime, in actuality, only a few people physically saw Kitty Genovese and her attacker; the others just heard the screams from Kitty Genovese.

In addition, of those who could see, none actually witnessed the stabbing take place (although one of the people who testified did see a violent action on behalf of the attacker.)

This contrasts with the widely held notion that all 38 people witnessed the initial stabbing.

Lastly, the second stabbing that resulted in the death of Catherine Genovese occurred in a stairwell which was not in the view of most of the initial witnesses; this deviates from the original article that stated that the murder took place on Austin Street in New York City in full view of at least 38 people.

This means that they would not have been able to physically see the murder take place. The potential inaccurate reporting of the initial case has not negated the bystander effect completely, but it has called into question its applicability and the incomplete nature of research concerning it.

Limitations of the Decision-Helping Model

Schroeder et al. (1995) believe that the decision-helping model provides a valuable framework for understanding bystander intervention.

Although primarily developed to explain emergency situations, it has been applied to other situations, such as preventing someone from drinking and driving, to deciding to donate a kidney to a relative.

However, the decision model does not provide a complete picture. It fails to explain why ‘no’ decisions are made at each stage of the decision tree. This is particularly true after people have originally interpreted the event as an emergency.

The decision model doesn’t take into account emotional factors such as anxiety or fear, nor does it focus on why people do help; it mainly concentrates on why people don’t help.

Piliavin et al. (1969, 1981) put forward the cost–reward arousal model as a major alternative to the decision model and involves evaluating the consequences of helping or not helping.

Whether one helps or not depends on the outcome of weighing up both the costs and rewards of helping. The costs of helping include effort, time, loss of resources, risk of harm, and negative emotional response.

The rewards of helping include fame, gratitude from the victim and relatives, and self-satisfaction derived from the act of helping. It is recognized that costs may be different for different people and may even differ from one occasion to another for the same person.

Accountability Cues

According to Bommel et al. (2012), the negative account of the consequences of the bystander effect undermines the potential positives. The article “Be aware to care: Public self-awareness leads to a reversal of the bystander effect” details how crowds can actually increase the amount of aid given to a victim under certain circumstances.

One of the problems with bystanders in emergency situations is the ability to split the responsibility (diffusion of responsibility).

Yet, when there are “accountability cues,” people tend to help more. Accountability cues are specific markers that let the bystander know that their actions are being watched or highlighted, like a camera. In a series of experiments, the researchers tested if the bystander effect could be reversed using these cues.

An online forum that was centered around aiding those with “severe emotional distress” (Bommel et al., 2012) was created.

The participants in the study responded to specific messages from visitors of the forum and then rated how visible they felt on the forum.

The researchers postulated that when there were no accountability cues, people would not give as much help and would not rate themselves as being very visible on the forum; when there are accountability cues (using a webcam and highlighting the name of the forum visitor), not only would more people help but they would also rate themselves as having a higher presence on the forum.

As expected, the results fell in line with these theories. Thus, targeting one’s reputation through accountability cues could increase the likelihood of helping. This shows that there are potential positives to the bystander effect.

Neuroimaging Evidence

Researchers looked at the regions of the brain that were active when a participant witnessed emergencies. They noticed that less activity occurred in the regions that facilitate helping: the pre- and postcentral gyrus and the medial prefrontal cortex (Hortensius et al., 2018).

Thus, one’s initial biological response to an emergency situation is inaction due to personal fear. After that initial fear, sympathy arises, which prompts someone to go to the aid of the victim. These two systems work in opposition; whichever overrides the other determines the action that will be taken.

If there is more sympathy than personal distress, the participant will help. Thus, these researchers argue that the decision to help is not “reflective” but “reflexive” (Hortensius et al., 2018).

With this in mind, the researchers argue for a more personalized view that takes into account one’s personality and disposition to be more sympathetic rather than utilize a one-size-fits-all overgeneralization.

Darley, J. M., & Latané´, B. (1968). Bystander intervention in emergencies: Diffusion of responsibility . Journal of Personality and Social Psychology, 8 , 377–383.

Garcia, Stephen M, Weaver, Kim, Moskowitz, Gordon B, & Darley, John M. (2002). Crowded Minds. Journal of Personality and Social Psychology, 83 (4), 843-853.

Hortensius, Ruud, & De Gelder, Beatrice. (2018). From Empathy to Apathy: The Bystander Effect Revisited. Current Directions in Psychological Science, 27 (4), 249-256.

Latané´, B., & Darley, J. M. (1968). Group inhibition of bystander intervention in emergencies . Journal of Personality and Social Psychology, 10 , 215–221.

Latané´, B., & Darley, J. M. (1970). The unresponsive bystander: Why doesn’t he help? New York, NY: Appleton-Century-Croft.

Latané´, B., & Darley, J. M. (1976). Help in a crisis: Bystander response to an emergency . Morristown, NJ: General Learning Press.

Latané´, B., & Nida, S. (1981). Ten years of research on group size and helping . Psychological Bulletin, 89 , 308 –324.

Manning, R., Levine, M., & Collins, A. (2007). The Kitty Genovese murder and the social psychology of helping: The parable of the 38 witnesses. American Psychologist, 62 , 555-562.

Prentice, D. (2007). Pluralistic ignorance. In R. F. Baumeister & K. D. Vohs (Eds.), Encyclopedia of social psychology (Vol. 1, pp. 674-674) . Thousand Oaks, CA: SAGE Publications, Inc.

Rendsvig, R. K. (2014). Pluralistic ignorance in the bystander effect: Informational dynamics of unresponsive witnesses in situations calling for intervention. Synthese (Dordrecht), 191 (11), 2471-2498.

Shotland, R. L., & Straw, M. K. (1976). Bystander response to an assault: When a man attacks a woman. Journal of Personality and Social Psychology, 34 (5), 990.

Siegal, H. A. (1972). The Unresponsive Bystander: Why Doesn’t He Help? 1(3) , 226-227.

Van Bommel, Marco, Van Prooijen, Jan-Willem, Elffers, Henk, & Van Lange, Paul A.M. (2012). Be aware to care: Public self-awareness leads to a reversal of the bystander effect. Journal of Experimental Social Psychology, 48 (4), 926-930.