The bystander effect is a social psychological phenomenon that refers to cases in which individuals do not offer help to a victim. 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.
Social psychology research 
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 record 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.
Variables affect bystanders 
Emergency versus non-emergency situations 
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.
According to Latané and Darley, there are 5 characteristics of emergencies that affect bystanders 
- Emergencies involve threat of harm or actual harm
- Emergencies are unusual and rare
- The type of action required in an emergency differs from situation to situation
- Emergencies cannot be predicted/unexpected
- Emergencies require immediate action
Due to these five characteristics, bystanders go through cognitive and behavioral processes:
- Notice that something is going on
- Interpret the situation as being an emergency
- Degree of Responsibility felt
- Form of Assistance
- Implement the action choice
Notice To test the concept of "noticing," Latane and Darley (1968) staged an emergency using Columbia University students. The students were placed in a room-either alone, with two strangers or with three strangers to complete a questionnaire while they waited for the experimenter to return. While they were completing the questionnaire smoke was pumped into the room through a wall vent to simulate an emergency. When students were working alone they did noticed the smoke almost immediately (within 5 seconds). However, students that were working in groups were less likely or took longer (20 seconds) to notice the smoke. Latané and Darley claimed this phenomenon could be explained by the social norm of what is consider polite etiquette in public. In most western cultures, politeness dictates that it is inappropriate to idly look around. This may indicate that a person is nosy or rude. As a result, passers-by are more likely to be keeping their attention to themselves when around large groups than when alone. People who are alone are more likely to be conscious of their surroundings and therefore more likely to notice a person in need of assistance.
Interpret Once a situation has been noticed, in order for a bystander to intervene they must interpret the incident as an emergency. According to the of social influence, bystanders monitor the reactions of other people in an emergency situation to see if others think that it is necessary to intervene. If it is determined that others are not reacting to the situation, bystanders will interpret the situation as not an emergency and will not intervene. This is an example of pluralistic ignorance or social proof. Referring to the smoke experiment, even though students in the groups had clearly noticed the smoke which become so thick that it was obscuring their vision, irritating their eyes or causing them to cough, they were still unlikely to report it. Only one participant in the group condition reported the smoke within the first four minutes, and by the end of the experiment, no-one from five of eight groups had reported the smoke at all. In the groups that did not report the smoke, the interpretations of its cause, and the likelihood that it was genuinely threatening was also less serious, with no-one suggesting fire as a possible cause, but some preferring less serious explanations such as the air-conditioner was leaking. Similarly, interpretations of the context played an important role in people's reactions to a man and woman fighting in the street. When the woman yelled, "Get away from me; I don't know you," bystanders intervened 65 percent of the time, but only 19 percent of the time when the woman yelled "Get away from me; I don't know why I ever married you".
General bystander effect research was mainly conducted in the context of non-dangerous, non-violent emergencies. A study (2006) tested bystander effect in emergency situations to see if they would get the same results from other studies testing non-emergencies. In situations with low potential danger, significantly more help was given when the person was alone than when they were around another person. However, in situations with high potential danger, participants confronted with an emergency alone or in the presence of another person were similarly likely to help the victim. This suggests that in situations of greater seriousness it is more likely that people will interpret the situation as one in which help is needed and will be more likely to intervene.
Degree of Responsibility Darley and Latané determined that the degree of responsibility a bystander feels is dependent on three things:
- Whether or not they feel the person is deserving of help
- The competence of the bystander
- The relationship between the bystander and the victim
Forms of Assistance There are two categories of assistance as defined by Latané and Darley:
- Direct intervention: directly assisting the victim
- Detour intervention. Detour intervention refers to reporting an emergency to the authorities (i.e. the police, fire department)
Implementation After going through steps 1-4, the bystander must implement the action of choice.
In one study done by Abraham S. Ross, the effects of increased responsibility on bystander intervention were studied by increasing the presence of children. This study was based on the reaction of 36 male undergraduates presented with emergency situations. The prediction was that the intervention would be at its peak due to presence of children around those 36 male undergraduates participants. This was experimented and showed that the prediction was not supported and was concluded as "the type of study did not result in significant differences in intervention." 
A meta-analysis (2011) of the bystander effect  reported that "The bystander effect was attenuated when situations were perceived as dangerous (compared with non-dangerous), perpetrators were present (compared with non-present), and the costs of intervention were physical (compared with non-physical). This pattern of findings is consistent with the arousal-cost-reward model, which proposes that dangerous emergencies are recognized faster and more clearly as real emergencies, thereby inducing higher levels of arousal and hence more helping." They also "identified situations where bystanders provide welcome physical support for the potentially intervening individual and thus reduce the bystander effect, such as when the bystanders were exclusively male, when they were naive rather than passive confederates or only virtually present persons, and when the bystanders were not strangers."
An alternative explanation has been proposed by Stanley Milgram, who hypothesized that the bystanders′ callous behavior was caused by the strategies they had adopted in daily life to cope with information overload. This idea has been supported to varying degrees by empirical research.
Timothy Hart and Ternace Miethe used data from the National Crime Victimization Survey (NCVS) and found that a bystander was present in 65 percent of the violent victimizations in the data. Their presence was most common in cases of physical assaults (68%), which accounted for the majority of these violent victimizations and less likely in robberies (49%) and sexual assaults (28%). The actions of bystanders were most frequently judged by victims as "neither helping nor hurting" (48%), followed by "helping" (37%), "hurting" (10%), and "both helping and hurting" (3%). Half of the attacks that a bystander was present at occurred in the evening where the victim and bystander were strangers.
Ambiguity and Consequences 
Ambiguity is one factor that affects whether or not a person assists another in need. In situations in which the bystander(s) are not sure if a person requires assistance (a high ambiguity situation), reaction time is slow (hearing a person fall but not sure if they are hurt). In low ambiguity situations (a person yelling out for help) reaction times for bystanders is quicker than high ambiguity situations. In some cases of high ambiguity, it can take a person or group up to 5 times more seconds before taking action than in cases of low ambiguity. The number of bystanders in each condition is not a significant factor. In these cases, bystanders determine their own safety in these cases before proceeding. Bystanders are more likely to intervene in low ambiguity, insignificant consequence situations than in high ambiguity, significant consequence situations.
Understanding of environment 
Whether or not a bystander intervenes may have to do with their familiarity of the environment where the emergency occurs. If the bystander is familiar with the environment, they are more likely to know where to get help, where the exits are, etc. Bystanders who are in an environment in which they are not familiar with the surroundings are less likely to give help in an emergency situation.
Priming the bystander effect 
Research done by Garcia et al. (2002) indicate that priming a social context may inhibit helping behavior. Imagining being around one other person or being around a group of people can affect a person's willingness to help.
In one study the effects of masculinity and the bystander effect were studied. Subjects participated in a simulated group discussion via headphones. One member of the group apparently had a choking fit and called for help. "Highly masculine" subjects were less likely to take action to help the victim than were other subjects. Femininity and actual gender had no effect on likelihood of helping. Results are interpreted according to past research evidence that "highly masculine" subjects fear potential embarrassment and loss of poise, so they may be reluctant to intervene in emergencies.
Cohesiveness and group membership 
Group cohesiveness is another variable that can affect the helping behavior of a bystander. As defined by Rutkowski et al,, cohesiveness refers to an established relationship (friends, acquaintances) between two or more people. Experiments have been done to test the performance of bystanders when they are in groups with people they have been acquainted with. According to Rutkowski et al., the social responsibility norm affects helping behavior. The norm of social responsibility states that "people should help others who are in need of help and who are dependent on them for it. As suggested by the research, the more cohesive a group, the more likely the group will act in accordance to the social responsibility norm. To test this hypothesis, researchers used undergraduate students and divided them into four groups: a low cohesive group with two people, a low cohesive group with four people, a high cohesive group with two people and a high cohesive group with four people. Students in the high cohesive group were then acquainted with each other by introducing themselves and discussing what they liked/disliked about school and other similar topics. The point of the experiment was to determine whether or not high cohesive groups were more willing to help a hurt "victim" than the low cohesive groups. The four member high cohesive groups were the quickest and most likely groups to respond to the victim who they believed to be hurt. The four member low cohesive groups were the slowest and least likely to respond to the victim.
Altruism research suggests that helping behaviour is more likely when there are similarities between the helper and the person being helped. Recent research has considered the role of similarity, and more specifically, shared group membership, in encouraging bystander intervention. In one experiment (2005), researchers found that bystanders were more likely to help an injured person if that person was wearing a football jersey of a team the bystander liked as opposed to a team the bystander did not like. However, when their shared identity as football fans was made salient, supporters of both teams were likely to be helped, significantly more so than a person wearing a plain shirt.
The findings of Mark Levine and Simon Crowther (2008) illustrated that increasing group size inhibited intervention in a street violence scenario when bystanders were strangers but encouraged intervention when bystanders were friends. They also found that when gender identity is salient group size encouraged intervention when bystanders and victim shared social category membership. In addition, group size interacted with context-specific norms that both inhibit and encourage helping. The bystander effect is not a generic consequence of increasing group size. When bystanders share group-level psychological relationships, group size can encourage as well as inhibit helping.
These findings can be explained in terms of self-categorization and empathy. From the perspective of self-categorization theory, a person’s own social identity, well-being is tied to their group membership so that when a group based identity is salient, the suffering of one group member can be considered to directly affect the group. Because of this shared identity, referred to as self-other merging, bystanders are able to empathize, which has been found to predict helping behaviour. For example, in a study relating to helping after eviction both social identification and empathy were found to predict helping. However, when social identification was controlled for, empathy no longer predicted helping behaviour.
Personality and background 
No significant results have been reported to suggest that a person's personality will affect whether or not they help. Research results also indicate that socioeconomic status is not an significant factor in helping behavior.
Rape myths and bystander attitudes 
More research is being done to determine how rape myths affects bystanders when they see or hear of a rape. Rape myths are defined as prejudicial, stereotyped, or false beliefs about rape, rape victims and rapists. It is also defined as attitudes and beliefs that are generally false yet widely and persistently held and that serve to deny and justify male sexual aggression against women. Significant findings indicate that males, students who plan to pledge a fraternity/sorority, athletes, students without previous education on rape and students who do not know anyone who has been sexually assaulted are more likely to believe rape myths and less likely to intervene when a person is being raped. Not enough research has been on rape myths and bystander attitudes for different ethnicities to make any generalizations based on race.
Diffusion of responsibility 
Darley and Latané (1968) conducted research on diffusion of responsibility. The findings suggest that, in the case of an emergency, when people believe that there are other people around they are less likely or slower to help a victim because they believe someone else will take responsibility. People may also fail to take responsibility for a situation depending on the context. They may assume that other bystanders are more qualified to help, such as doctors or police officers, and that their intervention would be unneeded. They may also be afraid of being superseded by a superior helper, offering unwanted assistance, or facing the legal consequences of offering inferior and possibly dangerous assistance. An example is the limitation of California's Good Samaritan Law, limiting liability for those attempting to provide medical services as opposed to non-medical (extraction from automobile) services.
Organizational Ombuds practitioners' research 
A 2009 study published by International Ombudsman Association in the Journal of the International Ombudsman Association suggests that—in reality—there are dozens of reasons why people do not act on the spot or come forward in the workplace when they see behavior they consider unacceptable.
The most important reasons cited for not acting were: the fear of loss of important relationships in and out of the workplace, and a fear of "bad consequences." There also were many reasons given by people who did act on the spot or come forward to authorities.
This practitioners' study suggests that the "bystander effect" can be studied and analyzed in a much broader fashion. The broader view includes not just a) what bystanders do in singular emergencies, b) helping strangers in need, when c) there are (or are not) other people around. The reactions of bystanders can also be analyzed a) when the bystanders perceive any of a wide variety of unacceptable behavior over time, b) they are within an organizational context, and c) with people whom they know. The practitioners' study reported many reasons why some bystanders within organizations do not act or report unacceptable behavior. The study also suggests that bystander behavior is, in fact, often helpful, in terms of acting on the spot to help,and reporting unacceptable behavior (and emergencies and people in need.) The ombuds practitioners' study suggests that what bystanders will do in real situations is actually very complex, reflecting views of the context and their managers (and relevant organizational structures if any) and also many personal reasons.
In support of the idea that some bystanders do indeed act responsibly, there is an important 2010 article about a survey of investigators funded by the US National Institutes of Health that shows that informal intervention by peers and bystanders can interrupt or remedy unacceptable scientific behavior. See Gerald Koocher and Patricia Keith-Spiegel's "Peers Nip Misconduct in the Bud" (July 22, 2010) Nature 466, 438-440 How Do Researchers Respond to Perceived Scientific Wrongdoing? Overview, Method and Survey Results.
Implications of research 
South African murder trials 
In an effort to make South African courts more just in their convictions, the concept of extenuating circumstances came into fruition. However, no concrete definition of extenuating circumstances was ever made. The South African courts began using the testimony of expert social psychologists to define what extenuating circumstances would mean in the justice system. Examples include: deindividuation, bystander apathy, and conformity. In the case of S. vs. Sibisi and Others (1989) eight members of the South African Railways and Harbours Workers' Union were involved in the murder of five workers who chose not to join in the SARHWU strike. Psychologists Scott Fraser and Andrew Colman presented evidence for the defense using research from social psychology. Social anthropologist, Boet Kotzé provided evidence for the defense as well. He testified that African cultures are characterized by a collective consciousness. Kotzé testified that the collective conscious contributed to the defendants' willingness to act with the group rather than act as individuals. Fraser and Colman that bystander apathy, deindividuation, conformity and group polarization were extenuating factors in the killing of the four strike breakers. They explained that Deindividuation may affect group members' ability to realize that they are still accountable for their individual actions even when with a group. They also used research on bystander apathy by Latané and Darley to illustrate why four of the eight defendants watched as the other four defendants killed four men. The testimonies of Fraser and Colman did help four of the defendants escape the death penalty.
Some parts of the world have included laws keep bystanders responsible when they witness an emergency.
- The Charter of human rights and freedoms of Quebec makes it mandatory to "come to the aid of anyone whose life is in peril, either personally or calling for aid, unless it involves danger to himself or a third person, or he has another valid reason". It is therefore a legal obligation to assist people in Quebec.
- Likewise, the Brazilian Penal Code states that it is a crime not to rescue (or call emergency services when appropriate) injured or disabled people including those found under grave and imminent danger as long as it safe to do so. This also includes abandoned children.
In the USA, Good Samaritan laws have been implemented to protect bystanders who acted in good faith. For more information on Good Samaritan laws by state, refer to: HeartSafe America Many organizations are including bystander training. For example, the United States Department of the Army is doing bystander training with respect to sexual assault. Some organizations routinely do bystander training with respect to safety issues. Others have been doing bystander training with respect to diversity issues. Organizations such as American universities are also using bystander research to improve bystander attitudes in cases of rape. Examples include the InterAct Sexual Assault Prevention program  and the Green Dot program.
Many institutions have worked to provide options for bystanders who see behavior they find unacceptable. These options are usually provided through complaint systems - so bystanders have choices about where to go. One option that is particularly helpful is that of an organizational ombudsman, who keeps no records for the employer and is near-absolutely confidential.
What Would you Do? 
John Quiñones' primetime show, What Would You Do? on ABC, tests the bystander effect. Actors are used to act out non-emergency situations while the cameras capture the reactions and actions of innocent bystanders. Topics include cheating on a millionaire test, an elderly person shoplifting, racism and homophobia.
Non-computer versus computers: computer mediated intervention 
Research suggests that the bystander effect may be present in computer-mediated communication situations. Evidence demonstrates that people can be bystanders even when they cannot see the person in distress. In the experiment, 400 online chat groups were observed. One of two confederates were used as victims in each chat room: either a male victim whose screen name was Jake Harmen or a female victim whose screen name was Suzy Harmen. The purpose of the experiment was to determine whether or not the gender of the victim mattered, if the size of each chat group had any effect and if asking for a person's help by directly using their screen name would have any effect. Results indicated that the gender of the victim had no effect on whether or not a bystander assisted the victim. Consistent with findings of Latané and Darley, the number of people present in the chat room did have an effect. The response time for smaller chat groups was quicker than in the larger chat groups. However, this effect was nonexistent when the victim (Suzy or Jake) asked for help from a specific person in the chat group. The mean response time for groups in which a specific person was called out was 36.38 seconds. The mean response time for groups in which no screen name was pointed out was 51.53 seconds. A significant finding of the research is that intervention depends on whether or not a victim asked for help by specifying a screen name. The group size effect was inhibited when the victim specifically asked a specific person for help. The group size effect was not inhibited if the victim did not ask a specific person for help.
Children as bystanders 
Although most research has been conducted on adults, children can be bystanders too. A study conducted by Robert Thornberg in 2007 came up with seven reasons why children do not help when another classmate is in distress. These include: trivialisation, dissociation, embarrassment association, busy working priority, compliance with a competitive norm, audience modelling, and responsibility transfer. In a further study, Thornberg concluded that there are seven stages of moral deliberation as a bystander in bystander situations among the Swedish schoolchildren he observed and interviewed: (a) noticing that something is wrong, i.e., children pay selective attention to their environment, and sometimes they don't tune in on a distressed peer if they're in a hurry or their view is obstructed, (b) interpreting a need for help - sometimes children think others are just playing rather than actually in distress or they display pluralistic ignorance, (c) feeling empathy, i.e., having tuned in on a situation and concluded that help is needed, children might feel sorry for an injured peer, or angry about unwarranted aggression (empathic anger), (d) processing the school's moral frames - Thornberg identified five contextual ingredients influencing children's behavior in bystander situations (the definition of a good student, tribe caring, gender stereotypes, and social-hierarchy-dependent morality), (e) scanning for social status and relations, i.e., students were less likely to intervene if they didn't define themselves as friends of the victim or belonging to the same significant social category as the victim, or if there were high-status students present or involved as aggressors - conversely, lower-status children were more likely to intervene if only a few other low-status children were around, (f) condensing motives for action, such as considering a number of factors such as possible benefits and costs, and (g) acting, i.e., all of the above coalesced into a decision to intervene or not. It is striking how this was less an individual decision than the product of a set of interpersonal and institutional processes.
Notable examples 
Kitty Genovese 
The case of Kitty Genovese is often cited as an example of the "bystander effect". It is also the case that originally stimulated social psychological research in this area. On March 13, 1964 Genovese, 28 years old, was on her way back to her Queens, New York, apartment from work at 3am when she was stabbed to death by a serial rapist and murderer. According to newspaper accounts, the attack lasted for at least a half an hour during which time Genovese screamed and pleaded for help. The murderer attacked Genovese and stabbed her, then fled the scene after attracting the attention of a neighbor. The killer then returned ten minutes later and finished the assault. Newspaper reports after Genovese's death claimed that 38 witnesses watched the stabbings and failed to intervene or even contact the police until after the attacker fled and Genovese had died. This led to widespread public attention, and many editorials.
According to an article published in American Psychologist in 2007, the original story of Genovese's murder was exaggerated by the media. Specifically, there were not 38 eyewitnesses, the police were contacted at least once during the attack, and many of the bystanders who overheard the attack could not actually see the event. The authors of the article suggest that the story continues to be misrepresented in social psychology textbooks because it functions as a parable and serves as a dramatic example for students.
Axel Casian 
On June 16, 2008, on a country road outside Turlock, California, friends, family and strangers, including a volunteer fire chief, stood by as Sergio Aguiar methodically stomped his two-year-old son Axel Casian to death, explaining in a calm voice that he "had to get the demons out" of the boy. He stopped at one point to turn on the hazard lights on his truck. No one moved to take the child or attack Aguiar. Witnesses said they were all afraid to intervene because Aguiar "might have something in his pocket", although some people looked for rocks or boards hoping to find something to subdue him. The fire chief's fiancee called 911. Police officer Jerry Ramar arrived by helicopter and told Aguiar to stop. Aguiar gave Ramar the finger and Ramar shot him in the head. Police officers and psychologists later explained that the inaction of the crowd was justified in that "ordinary people aren't going to tackle a psychotic," that they were not "psychologically prepared" to intervene, and that being frozen in indecision and fear is a normal reaction.
Larry Froistad (1998) 
On Monday March 22, 1998, Larry Froistad posted a message in a chat room used as a support group for people battling alcoholism. In his message, he confessed to purposely getting drunk and setting his house on fire thus killing his daughter. Over 200 people were online to see the message. Many were outraged but some came to Froistad's defense and claimed that he was "experiencing a fantasy driven by guilt over his divorce." After a debate, three people out of 200+ reported the murder to the authorities. Mr. Froistad confessed to the murder on March 27, 1998.
Esmin Green, Kings County Hospital 
In June 2008 49-year-old Esmin Green collapsed in the waiting room of Kings County Hospital Center in Brooklyn after waiting nearly 24 hours for treatment. She was ignored by other people present in the room and two security guards. She was helped after an hour passed but died. The hospital staff falsified their records to minimize the time she had lain on the floor unaided. Kings County Hospital had been previously cited for unsanitary conditions and patient neglect.
Hugo Alfredo Tale-Yax 
In April 2010 Hugo Alfredo Tale-Yax was stabbed to death in New York City after coming to the aid of a woman who was being attacked by a robber. Yax was on the sidewalk for more than an hour before firefighters arrived. Almost twenty-five people walked by while he lay dying on a sidewalk in Queens, several stared at Yax; one of them took pictures, however none of them helped or called emergency services.
Raymond Zack 
On Memorial Day, 2011, 53-year-old Raymond Zack, of Alameda, California, walked into the waters off Robert Crown Memorial Beach and stood neck deep in water roughly 150 yards offshore for almost an hour. His foster mother, Dolores Berry, called 9-1-1 and said that he was trying to drown himself. (There are conflicting reports about Zack's intentions.) Firefighters and police responded but did not enter the water. The firefighters called for a United States Coast Guard boat to respond to the scene. According to police reports, Alameda police expected the firefighters to enter the water. Firefighters later said that they did not have current training and certifications to perform land-based water rescue. Dozens of civilians on the beach, and watching from their homes across from the beach, did not enter the water, apparently expecting public safety officers to conduct a rescue. Eventually, Zack collapsed in the water, apparently from hypothermia. Even then, nobody entered the water for several minutes. Finally, a good samaritan entered the water and pulled Zack to shore, after which he died.
Wang Yue 
In October 2011, a two-year-old girl, Wang Yue, was hit by a small, white van in the city of Foshan, China, then run over by a large truck when she was not moved by bystanders. A total of 18 people ignored her, some going so far as to walk around the blood. The girl was left for 7 minutes before a recycler, Chen Xianmei, picked up the toddler and called for help. The child died eight days later.
See also 
- Collective action
- Diffusion of responsibility
- Duty to rescue
- Empathy-altruism hypothesis
- Good Samaritan law
- Herd behavior
- Hive mind
- Moral hazard
- Norm (sociology)
- Not in my backyard
- Social alienation
- Social influence
- Somebody Else's Problem
- What Would You Do?
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- Charter of human rights and freedoms Section 2
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- See also http://www.clemson.edu/olweus/ for an overview of a use of the Olweus Bullying Prevention Program.
- Ahrens, C. E., Rich, M. D., & Ullman, J. B. (2011). Rehearsing for real life: The impact of the InterACT sexual assault prevention program on self-reported likelihood of engaging in bystander interventions. Violence Against Women, 17(6), 760-776. doi:http://dx.doi.org/10.1177/1077801211410212
- Coker, A. L., Cook-Craig, P., Williams, C. M., Fisher, B. S., Clear, E. R., Garcia, L. S., & Hegge, L. M. (2011). Evaluation of green dot: An active bystander intervention to reduce sexual violence on college campuses. Violence Against Women, 17(6), 777-796. doi:http://dx.doi.org/10.1177/1077801211410264
- Markey, P.M. (2000). Bystander intervention in computer-mediated communication. Computers in Human Behavior, 16(2), 183-188. doi: 10.1016/S0747-5632(99)00056-4
- Thornberg, R (2007). "A classmate in distress: schoolchildren as bystanders and their reasons for how they act.". Social Psychology of Education 10: 5–28.
- Thornberg, Robert (2010). "A student in distress: Moral frames and bystander behavior in school". Elementary School Journal 110 (4): 585–608.
- 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 (6): 555–562. doi:10.1037/0003-066X.62.6.555. PMID 17874896.
- "Sergio Axel Casian". findagrave.com, Retrieved on 2012-01-09
- "Inaction in boy's killing called justified". SFGate, 2008-06-18. Retrieved on 2011-08-04.
- "Authorities Baffled over Toddler Killing". CBS News, 2008-06-16. Retrieved on 2011-07-04.
- Harmon, A. (1998, April 30). On-line trail to an off-line killing. The New York Times. Retrieved from http://www.nytimes.com/1998/04/30/us/on-line-trail-to-an-off-line-killing.html?pagewanted=all&src=pm
- "Video Shows Woman Ignored While Dying in New York Mental Hospital - Local News | News Articles | National News | US News". FOXNews.com. 2008-07-01. Retrieved 2011-10-27.
- Woman who died on hospital floor called 'beautiful person' CNN News, page found 2012-07-22.
- Livingston, Ikimulisa (2010-04-24). "A homeless man dies and nearly 25 people in Queens keep walking by". NYPOST.com. Retrieved 2011-10-27.
- "More Than 20 People Passed As Homeless New York Man Bled To Death". Gawker. Retrieved 30 November 2010.
- Many issues about this incident are disputed. Roughly one year after the incident, Raymond Zack's family filed a "Failure of Duty" lawsuit against the City of Alameda and the County of Alameda.
- Alameda police released redacted police reports to the media after the event that confirm this.
- "Alameda Police Release Memorial Day Drowning 911 Calls". San Francisco. 2011-06-08.
- "The Death of Raymond Zack: No Heroes, Only Bystanders". 2011-06-01.
- "Such callous disregard for life". Orange County. 2011-06-10.
- "Chinese toddler run over twice after being left on street". London: Telegraph. 2011-10-17. Retrieved 2011-10-27.
- Posted: Oct 22, 2011 5:03 PM ET (2011-10-22). "The bystander effect - Canada - CBC News". Cbc.ca. Retrieved 2011-10-27.