Chapter 12: Social Psychology: Groups, Prejudice, and Aggression¶

Summary¶

This chapter scales up from individual social influence to group dynamics and intergroup relations. Students examine social loafing, deindividuation, groupthink, and group polarization, then study the Milgram obedience experiment in depth. Prejudice and discrimination are explored through implicit attitudes, in-group bias, out-group homogeneity bias, the just-world phenomenon, confirmation bias, belief perseverance, and self-fulfilling prophecy. The chapter closes with prosocial behavior — altruism and the bystander effect / diffusion of responsibility — alongside locus of control and the mere exposure effect.

Concepts Covered¶

This chapter covers the following 18 concepts from the learning graph:

Group Polarization
Diffusion of Responsibility
Deindividuation
Milgram Obedience Study
Mere Exposure Effect
Prejudice and Discrimination
Belief Perseverance
Groupthink
Social Loafing
Bystander Effect
Self-Fulfilling Prophecy
Implicit Attitudes
In-Group Bias
Confirmation Bias
Altruism
Locus of Control
Just-World Phenomenon
Out-Group Homogeneity Bias

Prerequisites¶

This chapter builds on concepts from:

Chapter 11: Social Psychology: Attitudes, Attribution, and Influence

12.1 Group Dynamics¶

Mascot-welcome

Psy the Owl welcoming you to Chapter 12 Welcome to Chapter 12 — the darker side of social psychology!

Chapter 11 showed you how individual people influence each other. Now we zoom out: what happens when people act as part of a group? The answer, often, is that behavior becomes more extreme, more risky, more hostile, or more passive than any individual would be alone. Groups produce phenomena that their members would deny in isolation.

This chapter includes the Milgram study — possibly the most disturbing and most important experiment in the history of psychology. It ends with the question of why people sometimes don't help when help is desperately needed. Both topics will change how you see human nature.

Let's think about that! 🦉

Social loafing is the tendency for individuals to exert less effort when working in a group than when working alone. Ringelmann's original rope-pulling experiments found that individuals pulled less hard as group size increased. The pattern is consistent: people work harder when their individual contribution is identifiable and harder when they are working alone.

Social loafing occurs because: - Diffused responsibility: Each person's contribution is less identifiable, reducing accountability. - Reduced evaluation apprehension: If no one can tell how hard you worked, the social pressure to perform is lower. - Free riding: If others will do the work, the individual benefit of personal effort decreases.

Social loafing is reduced when: individual contributions are identifiable, the task is meaningful or personally involving, the group is small, or cohesion is high (members feel strongly connected to each other's goals).

Deindividuation¶

Deindividuation is the loss of self-awareness and self-restraint that occurs in group situations characterized by anonymity, arousal, and diffused responsibility. When people feel less individually identifiable, they are more likely to engage in behaviors — aggression, impulsive action, norm violation — they would suppress when personally accountable.

Classic demonstrations include the increased aggression of people in Halloween costumes (Philip Zimbardo's research), the behavior of online users behind anonymous handles, and the behavior of crowds and mobs. The classic explanation is that group membership and anonymity shift attention away from internal standards and toward immediate group norms and situational cues.

Groupthink¶

Groupthink is the tendency of cohesive groups under pressure to prioritize consensus over critical thinking, producing poor decisions. Irving Janis developed the concept after studying major U.S. foreign policy failures, including the Bay of Pigs invasion of Cuba and the decision to cross the 38th parallel in Korea.

Symptoms of groupthink include:

Illusion of invulnerability: Excessive optimism about group decisions.
Collective rationalization: Discounting warning signs or contrary evidence.
Belief in the group's inherent morality: Ignoring ethical considerations.
Stereotyped views of out-groups: Dismissing opponents as weak or evil.
Pressure on dissenters: Silencing members who raise concerns.
Self-censorship: Members don't voice doubts.
Illusion of unanimity: Silence is interpreted as agreement.
Self-appointed mindguards: Members shield the group from contrary information.

Groupthink is most likely in highly cohesive groups with directive leadership, under time pressure, in isolated settings. It can be reduced by assigning a "devil's advocate" role, seeking outside opinions, and separating idea generation from evaluation.

Group Polarization¶

Group polarization is the tendency for group discussion to make members' existing attitudes more extreme in the direction they were already leaning. If a group of mildly prejudiced individuals discusses a topic, post-discussion attitudes are typically more prejudiced. If a group of mildly risk-tolerant individuals deliberates together, they typically become more risk-tolerant.

Two mechanisms drive group polarization: - Persuasive arguments: During discussion, people hear more arguments supporting the prevailing view (since most members share it), strengthening those positions. - Social comparison: People learn the group's norm and shift toward or past it to appear appropriately aligned with group values.

Group polarization helps explain radicalization in online communities, jury deliberation outcomes, and organizational decision-making.

12.2 The Milgram Obedience Study¶

Stanley Milgram's obedience research (1961–1963) is arguably the most ethically complex and behaviorally revealing study in the history of psychology. Milgram designed it partly in response to the Holocaust — to understand how ordinary people could participate in extraordinary atrocities.

The procedure: Participants ("teachers") believed they were administering electric shocks to a "learner" (actually a confederate) each time the learner answered incorrectly on a memory task. The shock generator had switches labeled from 15 volts ("Slight Shock") to 450 volts ("XXX — Danger: Severe Shock"). The learner's protests (pre-recorded) escalated from grunts to screams to complete silence.

An authority figure (a researcher in a gray lab coat) gave commands to continue: "Please continue," "The experiment requires that you continue," "You have no other choice, you must go on."

The findings: Milgram expected perhaps 1–2% of participants to deliver the maximum shock. In his basic condition, approximately 65% of participants (26 of 40) delivered the full 450-volt shock, despite the learner's apparent suffering. All participants went to at least 300 volts.

Diagram: Milgram's Variables and Their Effects¶

Explore: What factors changed obedience rates in Milgram's variations?

Milgram ran over 20 variations of his experiment to identify the conditions that increase or decrease obedience:

Variables that INCREASED obedience: - Proximity of authority figure: When the experimenter was in the room (vs. giving instructions by phone), obedience was higher. - Physical distance from victim: When the teacher and learner were in separate rooms (teacher couldn't see or hear victim directly), obedience was higher. - Legitimacy of setting: Prestigious Yale University setting produced higher obedience than an anonymous office building. - Foot-in-the-door progression: Shock levels started small and escalated incrementally — each step seemed small.

Variables that DECREASED obedience: - Presence of peers who rebelled: When confederate "teachers" refused to continue, obedience rates dropped dramatically to ~10%. - Proximity to victim: When the victim was in the same room (or the teacher had to hold their hand on a shock plate), obedience dropped significantly. - Conflicting authority: When two experimenters disagreed about continuing, most participants stopped. - Moving setting away from legitimate institution: Non-institutional settings reduced obedience.

Key lesson: Obedience was not primarily a function of individual character (sadism, authoritarianism) but of situational factors — the legitimacy of authority, physical proximity, escalating commitment, and absence of alternative social models.

Milgram's interpretation emphasized the agentic state: when people subordinate themselves to an authority figure, they shift from acting as autonomous moral agents to acting as instruments of someone else's will. In the agentic state, people experience themselves as responsible for carrying out orders, not for the outcomes of those orders.

Mascot-thinking

Psy the Owl thinking Psy's Note: Milgram's study raised severe ethical concerns — participants were deceived, were exposed to genuine distress, and some showed lasting psychological effects. The study would not be permitted under modern ethical guidelines (APA, IRB). Yet it remains one of psychology's most important findings, because the situational determinism it revealed has been replicated in many forms and has profound implications for understanding atrocities, military behavior, organizational misconduct, and everyday compliance.

12.3 Prejudice and Discrimination¶

Prejudice is a negative attitude (affective, cognitive, and behavioral) toward members of a group based solely on their group membership. Discrimination is prejudice in action — differential treatment of individuals based on group membership.

In-Group Bias and Out-Group Homogeneity¶

In-group bias is the tendency to favor members of one's own group over members of out-groups. Henri Tajfel's minimal group paradigm showed that even arbitrary, meaningless group assignments (who overestimates dots) produce in-group favoritism. People identify with groups they belong to (religion, ethnicity, school, nation, sports team), and this identification generates positive feelings toward in-group members and comparative derogation of out-groups.

Out-group homogeneity bias is the tendency to see members of out-groups as more similar to each other than members of one's own in-group. "They're all alike; we're all individuals." This perceptual distortion reduces moral engagement with out-group members (it's easier to harm "them" when they're interchangeable) and supports stereotyping.

Implicit Attitudes¶

Implicit attitudes are evaluative associations that operate automatically and outside of conscious awareness. Unlike explicitly stated attitudes (which can be controlled), implicit attitudes are measured through reaction-time tests like the Implicit Association Test (IAT), which infers associations based on how quickly people pair concepts.

Implicit racial, gender, and age biases are widespread even among people who sincerely endorse egalitarian values. The relationship between implicit attitudes and behavior is modest and contextual — implicit attitudes predict behavior better in low-control situations (under cognitive load, time pressure) than in deliberate, reflective situations.

Confirmation Bias and Belief Perseverance¶

Confirmation bias is the tendency to seek, interpret, and remember information in ways that confirm one's existing beliefs. In the context of prejudice, confirmation bias means that encounters with out-group members that confirm the stereotype are noticed and remembered, while disconfirming encounters are explained away or forgotten.

Belief perseverance is the tendency to maintain beliefs even after the evidence for them has been discredited. In Lee Ross's classic debriefing experiments, participants shown that the basis for a belief was fabricated continued to hold modified versions of the belief. In prejudice contexts, belief perseverance means that even compelling counter-evidence may not immediately update stereotypic beliefs — the original association persists.

The Just-World Phenomenon¶

The just-world phenomenon is the belief that the world is fair — that people get what they deserve and deserve what they get. Melvin Lerner proposed this as a psychological need: because the alternative (that misfortune is random and can happen to anyone) is too threatening, people maintain a belief in cosmic fairness.

Consequences of just-world beliefs: - Victim blaming: If bad things happen to good people, the world would be unjust — so the victim must have done something to deserve it. ("She must have been drinking." "He shouldn't have been in that neighborhood.") - Reduced empathy: Believing victims are responsible reduces the perceived need to help. - Discrimination justification: If a group is economically disadvantaged, just-world beliefs can support attributing this to the group's own characteristics rather than structural factors.

Self-Fulfilling Prophecy¶

A self-fulfilling prophecy occurs when an expectation about a person or group causes behaviors that make the expectation come true. If a teacher believes a child is less capable and interacts with them accordingly (less time, less challenge, lower expectations), the child may in fact learn less — confirming the teacher's original (incorrect) expectation. Robert Rosenthal and Lenore Jacobson's "Pygmalion in the Classroom" demonstrated that teachers' randomly assigned expectations about students' "intellectual blooming potential" influenced students' actual intellectual gains.

12.4 Prosocial Behavior: The Bystander Effect and Altruism¶

Bystander Effect and Diffusion of Responsibility¶

The murder of Kitty Genovese in 1964 — in which witnesses reportedly failed to intervene or call police — prompted John Darley and Bibb Latané to study why people fail to help in emergencies when others are present.

The bystander effect is the finding that individuals are less likely to offer help in an emergency when other people are present. In a series of classic experiments, Darley and Latané found that the larger the group witnessing an emergency, the less likely (and more slowly) any individual would respond.

Diffusion of responsibility is the mechanism: when others are present, each person feels less personally responsible to act because responsibility is shared (or assumed to be shared) across the group. In a group of ten, each person may assume "someone else will call 911" — and no one does.

Additional mechanisms include pluralistic ignorance (each bystander looks at others' calm reactions and concludes "maybe this isn't an emergency") and evaluation apprehension (fear of looking foolish if you overreact to a non-emergency).

Practical implication: to maximize help in an emergency, specify a particular person ("You in the red jacket — call 911"), removing the anonymity that enables diffusion.

Mascot-neutral

Psy the Owl in neutral pose Psy's Note: The Kitty Genovese story was substantially inaccurate in its original reporting — fewer witnesses were present than reported, and some did call police. But the core experimental finding — that bystander presence reduces helping — has been robustly replicated in dozens of studies. The Genovese narrative should be treated as a cautionary tale about media framing, while the experimental evidence on the bystander effect remains solid.

Altruism¶

Altruism is behavior intended to benefit another at a cost to oneself. Genuinely altruistic behavior is an enduring puzzle for purely self-interest models of human behavior. Evolutionary explanations include:

Kin selection: Helping genetic relatives (who share genes) increases inclusive fitness.
Reciprocal altruism: Helping non-relatives who are likely to reciprocate in the future.
Group selection: Groups with altruistic members may outcompete less cooperative groups.

Psychological explanations note that helping often produces empathy-induced altruism (helping to relieve another's distress) or prosocial emotion (warm glow, gratitude, elevation). Whether "true" altruism exists — or whether all helping serves some form of self-interest (even psychological self-interest) — remains a philosophical and empirical debate.

12.5 Locus of Control and the Mere Exposure Effect¶

Locus of Control¶

Locus of control (Julian Rotter) is the degree to which people believe they control outcomes in their lives. People with an internal locus of control believe that outcomes depend on their own efforts and abilities — they are agents of their own fate. People with an external locus of control believe outcomes are determined by luck, fate, powerful others, or circumstances beyond their control.

Internal locus of control is associated with better physical health, higher academic achievement, greater persistence in the face of obstacles, and lower susceptibility to learned helplessness. External locus of control is associated with passivity, anxiety, and (in extreme form) the helplessness that can accompany depression.

Locus of control is not fixed — it is a learned orientation that can shift with experience. Importantly, it should match reality: an internal locus of control is adaptive when one genuinely can influence outcomes; in genuinely uncontrollable situations, accepting external control may actually be healthier (a concept related to "serenity to accept the things I cannot change").

Mere Exposure Effect¶

The mere exposure effect (Robert Zajonc) is the finding that simply being repeatedly exposed to a stimulus increases liking for it. The effect does not require conscious awareness of the prior exposure — subliminal presentations also produce increased liking. It applies to people, faces, products, words, and even nonsense syllables.

The mere exposure effect has practical implications for advertising, political campaigns, and social integration: simply being around people from another group more often can increase liking (though this is most effective when the contact is equal-status and cooperative, as Gordon Allport's contact hypothesis stipulates).

12.6 Chapter Review¶

Mascot-celebration

Psy the Owl celebrating Phenomenal work completing Chapter 12!

These two social psychology chapters have given you a powerful and sometimes unsettling lens. You now understand why ordinary people sometimes do terrible things in groups (Milgram, deindividuation, groupthink), why prejudice persists despite good intentions (implicit attitudes, confirmation bias, the just-world phenomenon), and why people sometimes fail to help (bystander effect, diffusion of responsibility). But you also understand the conditions that can reverse these effects — social allies, identifiability, and direct responsibility.

Chapter 13 turns inward to personality and motivation — what drives individual differences in how people think, feel, and pursue goals.