It’s a bright afternoon in a bustling city. At one of the busiest intersections, a man suddenly collapses on the sidewalk. All around him, commuters hurry to work, tourists take selfies, and street vendors sell newspapers and snacks.

As the man lies there, struggling to breathe, people glance at him, concerned. Some slow their pace, watching to see what others will do, yet no one steps forward. After all, in a crowd this large, someone must have already called for an ambulance, right? Maybe it’s not as serious as it looks, and he just needs to sit down. Maybe someone else, someone more qualified, will get involved. 

Several minutes pass, yet no one steps forward to assist. Surrounded by so many others, the sense of personal responsibility to help seems to quietly diminish. Eventually, someone finally realizes help isn’t on the way and they intervene. 

While we think we would immediately react in such a situation, the bystander effect suggests that most of us will either hesitate before helping or not assist at all. So why does this happen? 

Why Does the Bystander Effect Occur?

The bystander effect is attributed to three main factors: diffusion of responsibility, social influence, and pluralistic ignorance.¹ 

Diffusion of responsibility occurs when the presence of many witnesses causes each individual to feel less personally obligated to intervene. When people are part of a group, they often assume that someone else will step in to help, relieving them of personal responsibility (as we saw in the scenario above). The more bystanders there are, the more diluted each person’s sense of duty becomes. As a result, individuals may hesitate or choose not to act at all.

Social influence, on the other hand, refers to people looking to others’ reactions to decide how they themselves should respond.² In uncertain situations, especially emergencies that are confusing or ambiguous, individuals often take their cues from those around them. If other bystanders appear calm, indifferent, or passive, people are likely to interpret the situation as non-urgent, even if they initially sensed that something was wrong. This is very similar to conformity, when we adapt our behaviors to match those of the people around us. 

Finally, pluralistic ignorance is the belief that if other people aren’t reacting, it obviously isn’t an emergency. Pluralistic ignorance occurs when everyone in a group privately feels uncertain or concerned, but because no one visibly expresses those feelings, each person assumes that others see no cause for alarm. This leads to a situation where everyone is misled by the apparent calm or indifference of those around them.³

Confederate: In psychological research, a confederate is an individual who is secretly working with the experimenters while pretending to be another participant. Confederates are used to help create specific social situations or to manipulate variables without the real participants knowing.

Field Theory: Developed by psychologist Kurt Lewin, field theory explains behavior as a function of the individual and their environment. The theory emphasizes that a person’s actions are shaped by the total psychological environment, or “life space,” at a given moment. 

Life Space: A concept from Kurt Lewin’s field theory that refers to the total psychological environment influencing an individual at a given time. This includes their needs, goals, perceptions, and the surrounding social and physical environment. 

Game Theory: The study of mathematical models that describe how individuals make decisions when their outcomes depend not only on their own choices but also on the choices of others. It is commonly used to analyze strategic interactions in economics, politics, psychology, and social behavior. 

Volunteer’s Dilemma: A situation in which someone must step forward to help or solve a problem. This action comes at a personal cost for the volunteer, but everyone else benefits. As more potential helpers are present, each individual is less likely to volunteer, hoping that someone else will take responsibility instead.

External Validity: The extent to which the results of a study can be generalized beyond the specific conditions of the experiment to other people, settings, and times. A study with high external validity produces findings that are likely to apply in real-world situations.

The murder of Kitty Genovese

The bystander effect emerged as a result of a real-life emergency. In 1964, Kitty Genovese, a 28-year-old woman living in the neighborhood of Queens, New York, was raped and stabbed to death. Early reports claimed that dozens of her neighbors either witnessed or heard parts of the assault but failed to intervene or even call the police until it was too late. Newspapers at the time even reported on the number of people who remained silent. In The New York Times, the headline ran “³⁷ who saw murder didn’t call the police,” with the byline describing the event as “apathy.”⁶

Although later investigations revealed that the number of passive witnesses may have been exaggerated, the case ignited widespread concern and curiosity about why so many people could seemingly remain inactive during an emergency. Social psychologists Bibb Latané and John Darley were intrigued by the reported behavior of Kitty’s neighbors and sought to understand the phenomenon in greater detail. Through a series of experiments, they popularized the notion that the presence of other people can discourage individuals from helping in an emergency.⁷ 

In one study, Latané and Darley asked participants to complete a questionnaire in a room under one of three conditions: alone, with two other real participants, or with two confederates who were instructed to behave as if nothing unusual was happening.²⁴ As the participants worked, smoke slowly began to fill the room through a vent. When participants were alone, approximately 75% quickly noticed the smoke and reported it to the experimenters. However, when participants were placed with two other real participants, only about 38% reported the smoke. The most striking result came from the group of confederates who ignored the smoke. In this condition, only about 10% of participants reported the potential danger. 

This experiment demonstrated how the presence and behavior of others can significantly inhibit an individual’s likelihood of acting in an emergency scenario. Latané and Darley concluded that both diffusion of responsibility and social influence played critical roles: individuals were less likely to respond when they saw others remaining passive, and responsibility for taking action was perceived as shared among the group, reducing the sense of personal obligation.

Psychology goes social

However, the history of the bystander effect goes back further than the murder of Kitty Genovese. In 1936, the Society for the Psychological Study of Social Issues (SPSSI) was founded, marking a significant shift in psychology toward addressing social problems scientifically.⁸ Before the SPSSI’s formation, many psychologists believed that engaging with social issues might compromise the scientific integrity of their discipline. However, the hardships of the Great Depression in the 1930s sparked a shift in the public and academic mindset, as more people began to see psychology as a tool for addressing widespread societal conflicts. 

Central to this movement was Kurt Lewin, a German psychologist who fled the Nazi regime in 1933 and became a leading figure in American social psychology. Lewin stressed that understanding group dynamics was essential for solving social problems.⁹ In the 1940s, Lewin introduced field theory, which argued that human behavior is largely shaped by the situational contexts individuals find themselves in. He called this external psychological environment a person’s “life space,” which encompasses all the personal experiences, social forces, and psychological factors influencing the individual at a particular moment in time. In an emergency situation, a person’s “life space” can significantly impact their behavior. 

During the time of Lewin’s work on field theory, a broader cognitive revolution was occurring in psychology. As part of this shift, psychologists became more interested in how people think about and interpret their social environments. Lewin’s research into motivation and prosocial behavior fit into this new focus, as he explored what drives people to help others. However, by the 1960s, attention began to shift from why people help to why they sometimes fail to act.¹⁰ 

The evolution of the bystander effect

Since Latané and Darley’s initial research, the bystander effect has been revisited many times by researchers, each one offering nuance and new insights to the phenomenon. For instance, some studies show that the clarity of the emergency and the perceived danger to the helper heavily influence intervention. In ambiguous situations, people are still less likely to act, but when the emergency is clear and the risk to the helper is low, people are more likely to step in, even when others are present.¹⁷ 

Likewise, cognitive neuroscientists Ruud Hortensius and Beatrice de Gelder argue that helping behavior is shaped not just by situational factors like the presence of others, but also by neural and dispositional influences.¹² They conducted a review of studies that used brain scans and reaction tasks to assess people’s reactions to a variety of emergency situations and found that ​​brain regions involved in emotional and social processing, such as the amygdala and prefrontal cortex, play a role in determining responses to emergencies. More specifically, when participants thought other people were available to help, they were slower to react. This reaction happened automatically before participants could think about their response consciously. So, rather than a person not wanting to help in a situation, the bystander effect occurs partly because their brain hesitates when others are around. 

The researchers also stress that personal traits, including levels of empathy, personal distress, and moral reasoning, significantly affect whether an individual intervenes or remains passive. Empathy, for example,  can encourage someone to step in and help, but personal distress—feeling overwhelmed or anxious in a crisis—can actually make someone less likely to intervene.

The bystander effect has also been explored in digital contexts. In one study, students at Palermo University received an email from another ‘student’ requesting assistance with their thesis.²⁷ The students were randomly assigned to one of four conditions based on the presence or absence of other recipients (bystanders) and the presence or absence of a prosocial prime. In the priming condition, the request for help was included in a message that contained subtle reminders of helping and kindness. An image was also placed at the top of the page that encouraged the idea of being helpful to others. 

The findings revealed that participants were significantly less likely to respond when they believed the help request was sent to multiple recipients, suggesting that the bystander effect also occurs in online settings. However, the study also found that when the request for help was preceded by a prosocial prime, the likelihood of participants responding increased, even in the presence of multiple bystanders.

Kurt Lewin

A German-American psychologist of the early-mid 20th century, often regarded as the “father” of modern social psychology. He is best known for developing field theory, which emphasized the importance of situational and environmental factors in shaping behavior. Lewin’s work on group dynamics, leadership styles, and social change laid the foundation for later research in social, organizational, and developmental psychology.

Kitty Genovese

A young American woman living in Queens, New York, who worked as a bar manager. She became widely known after her murder in 1964, which was initially reported as having been witnessed by dozens of neighbors who failed to intervene. Her case sparked major public outrage and inspired research in psychology on the bystander effect.

Bibb Latané

American social psychologist best known for his pioneering research on the bystander effect and social influence. Along with John Darley, he conducted key experiments in the late 1960s that helped explain why people sometimes fail to help in emergencies when others are present. Latané has also made major contributions to understanding group behavior and the dynamics of crowd psychology.

John Darley

Along with Bibb Latané, American social psychologist John Darley conducted influential experiments that revealed how the presence of others can inhibit individuals from intervening in emergencies. Over his career, Darley also made important contributions to the study of morality, justice, and the psychology of decision-making. 

The bystander effect has serious consequences, both in everyday emergencies and in broader societal contexts. In most situations, the bystander effect has a negative impact. 

Delayed or absent emergency assistance

Going back to the murder of Kitty Genovese, official reports suggest that the crime went on for almost an hour before the emergency services eventually arrived.¹³ As studies tell us, people hesitate during situations of emergency, either because their brain is delaying their reaction or because they assume someone else has, or will, take action. This hesitation can cost critical minutes and worsen outcomes for victims. As Latané and Darley’s experiments show, even when emergencies are obvious (such as smoke billowing into a room), the presence of others reduces the likelihood that a single individual will step forward. 

Other research, however, suggests that when a person’s life is clearly in danger, bystander intervention becomes more likely. Researchers from the University of North Georgia analyzed databases of real-world emergencies involving bystander responses and found that the severity of the medical emergency and the victim’s condition strongly influenced whether help was given. In other words, bystanders were more likely to step in when the situation appeared life-threatening and the risk of death was higher.¹⁴

Increased tolerance for harmful behavior

Beyond emergencies, the bystander effect contributes to greater tolerance of harmful or unethical behavior in social groups, workplaces, and online communities. For instance, bullying, harassment, and discrimination can flourish when witnesses fail to intervene. There are three processes driving this inaction. First, the diffusion of responsibility means individuals may rationalize their inaction by thinking “it’s not my place” or “someone else will step in.” Second, social influence, particularly in school or workplace settings, can make people reluctant to speak out, especially when they don’t see anyone else reacting. And third, pluralistic ignorance may make people think that the harmful behavior is not that bad because others aren’t responding. Over time, this inaction can create environments where harmful behavior is normalized and victims feel abandoned, reinforcing cycles of abuse and injustice.

Changing bystander responses is extremely important for disrupting harmful behaviors such as sexual violence or bullying. Research shows that sexual violence often persists because of community and cultural norms that discourage intervention, reflecting a broader pattern related to the bystander effect.^25,26 Just as individuals may hesitate to act in emergencies when others are present, community members may fail to challenge harmful behaviors when they believe it is someone else’s responsibility. However, as a group of psychologists at the University of Hampshire argues, by mobilizing prosocial behavior among bystanders, a larger shift in community responses can be achieved.¹⁵

Volunteer’s Dilemma

The bystander effect can be understood using a concept from game theory called the volunteer’s dilemma.⁴ In this dilemma, everyone benefits if someone helps, but helping usually comes at a personal cost, such as time, effort, or risk. Because of this cost, each individual hopes that someone else will step in so they don’t have to. As more people are present, each person feels less pressure to act, thinking, “someone else will do it.” Consequently, when there are many potential helpers, the chance that any one individual will help drops closer to zero, because everyone is relying on someone else to volunteer.

The bystander effect has stood the test of time and is still regarded as a solid theory for understanding how people react in emergency or unsettling situations. However, since the 1960s, further research has uncovered a more complex and nuanced understanding of the phenomenon. As discussed so far, newer research suggests that the bystander effect is more complex than the earlier belief that groups are less likely to help someone in trouble than a lone individual. Other factors, such as the severity of a person’s medical situation,  our neurological processes, and social priming, also play a role in this effect. 

Was the bystander effect present at Kitty’s murder?

The main event on which most bystander effect research rests may not have been an example of the bystander effect at all. Critics of early bystander research argue that the original narrative framed the public as cold and indifferent, when in fact newer evidence suggests that the truth was more complex and less damning.¹⁶ The story of Kitty’s uncaring neighbors started to emerge two weeks after her murder, calling into question the validity of the claims.¹⁷ In addition, testimonies from the trial suggest that people did call the police or that some people simply didn’t know what was happening. Some have even shown that there is no evidence for the presence of 38 witnesses, or that witnesses observed the murder, or that witnesses remained inactive.¹⁸ As such, what has become a classic example of the bystander effect is now perceived by some to be overdramatized, leading to misconceptions about how often and how severely it happens.

Overgeneralized findings

Apart from the questionable evidence from Kitty’s murder, the early research into the bystander effect was largely conducted in laboratory settings. External validity, or the extent to which a study’s findings can be generalized to other contexts or groups, is an important factor to take into account when considering these early experiments. While lab studies provided valuable initial insights into helping behavior, they often involved low-stakes, clearly structured scenarios, such as smoke filling a room or hearing a staged accident. In contrast, Rachel Manning, Mark Levine, and Alan Collins highlight that real emergencies are more complex and involve emotional, social, and contextual factors that the early lab experiments failed to capture.¹⁶

Does the bystander effect even exist at all?

Recent research now calls into question the existence of the bystander effect entirely. Richard Philpot and his colleagues at Lancaster University analyzed surveillance footage of violent incidents in the UK, South Africa, and the Netherlands.¹⁹ Contrary to the traditional view of the bystander effect, they found that in 90 percent of cases, at least one bystander—and often several—stepped in to help. Moreover, their findings showed that the likelihood of intervention actually increased with the number of bystanders, directly challenging the original bystander effect theory. Interestingly, the researchers also found consistent intervention rates across all three countries, even though South Africa has lower perceived public safety and higher rates of violence. Philpot argues that this points to a strong natural tendency for people to help others in distress, regardless of cultural or societal differences.

The bystander effect across racial lines

Data from the United States’ National Emergency Management Information Systems (NEMIS) database shows that only 1 in 39 people in medical emergency situations receive bystander help.²⁰ However, according to that statistic, the color of a person’s skin and background also influence the support they get. 

Unfortunately, the bystander effect is subject to the same racial inequalities found across modern society. A study by sociologists at Cornell University found that Black patients are less than half as likely as White patients to receive help from bystanders during medical emergencies.²¹ The authors claim that this gap isn’t explained by differences in wealth or income in the areas where the incidents happen. However, they do believe that it may be partly due to residential segregation, which can leave Black patients living in neighborhoods with fewer services and support systems. They suggest that racial bias may play a role, affecting how Black individuals are viewed and treated in public spaces.

In the wake of George Floyd’s murder by a police officer in 2020, researchers have been looking at the relationship between racial bias and people’s failure to intervene in critical situations. Audrey Murrell, from the University of Pittsburgh, looked at the bystander effect and how it relates to aversive racism.²² Murrell highlights that even individuals who believe they hold no racist attitudes can unconsciously contribute to racial injustice through inaction during events such as George Floyd’s murder. Aversive racism refers to this disconnect, where people consciously support equality but still harbor unconscious biases that affect their behavior. In the context of the bystander effect, these hidden biases can make witnesses less likely to intervene when they see racial discrimination or violence. 

The bystander effect in children

The bystander effect is most often talked about in relation to adults, but research suggests that the phenomenon may develop at an early age. Many studies have shown that children are naturally helpful and willing to assist others.²³ But does this altruism remain when others are present? 

Maria Plötner et al. designed an experiment to test whether the presence of passive bystanders would reduce children’s helping behavior.²⁸ Children were placed in three conditions: alone, with bystanders who could help, and with bystanders who were present but unable to help (behind a barrier). The researchers found that children helped significantly less often when other potential helpers were present and available, compared to when they were alone or when the bystanders were unable to help. 

The results suggest that young children experience a diffusion of responsibility similar to that seen in adults. Importantly, helping rates were high when children were either alone or when bystanders were physically unable to intervene, indicating that shyness or social referencing were not the main reasons for the reduced helping. Instead, it was the sense that “someone else can help” that reduced children's willingness to act. The researchers confirmed this interpretation through follow-up interviews, where children in the bystander condition were much less likely to say it was their personal responsibility to help, compared to those in the other conditions.

Why are we more likely to offer help to a specific individual than a vague group? 

In this article, we explore why people are more likely to feel empathy and take action when they hear about a single, specific individual rather than a large, anonymous group. Emotional responses are typically stronger when a victim is identifiable, even if the broader problem affects far more people. This bias has important implications for how appeals for help are framed, especially in media, charity campaigns, and emergency situations. 

Social Loafing

Being in a group not only impacts our willingness to respond in an emergency—we also tend to put in less effort on any given assignment when they are working in a group. In this article, we look at the phenomenon of social loafing, where being part of a group makes us… well, lazy. 

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