Famous Psychology Experiments

Throughout psychology's history, groundbreaking experiments have shaped our understanding of human behavior, cognition, and development. While some of these studies couldn't be conducted today due to ethical concerns, they provided crucial insights that continue to influence psychology. Understanding these landmark experiments helps us appreciate how psychological knowledge has evolved and why ethical guidelines are essential.

The Milgram Obedience Experiments (1961-1963)

Stanley Milgram's obedience studies remain among psychology's most famous and controversial experiments, revealing disturbing truths about human nature.

Background: Following World War II and the Holocaust, Milgram wanted to understand how ordinary people could commit atrocities under authority pressure. The Experiment: Participants believed they were in a learning study where they administered electric shocks to a "learner" (actually an actor) for wrong answers. The shock levels increased from 15 to 450 volts, labeled from "Slight Shock" to "Danger: Severe Shock." An authority figure (experimenter in a lab coat) urged participants to continue despite the learner's protests and screams. Findings: Surprisingly, 65% of participants administered the maximum 450-volt shock, even when the learner stopped responding. Many showed extreme stress but continued when the authority figure insisted. Significance: The study demonstrated that ordinary people could perform harmful acts under authority pressure, challenging assumptions about moral behavior. It showed that situational factors could override personal ethics. Ethical Concerns: Participants experienced severe emotional distress, believing they were hurting someone. The deception and potential psychological harm led to stricter ethical guidelines for research. Modern Applications: Understanding obedience to authority helps explain workplace misconduct, military atrocities, and why people follow harmful orders. It emphasizes the importance of teaching people to question authority when necessary.

The Stanford Prison Experiment (1971)

Philip Zimbardo's prison simulation revealed how quickly people adopt roles and how situations can corrupt behavior.

The Setup: Twenty-four male college students were randomly assigned as "guards" or "prisoners" in a mock prison in Stanford's psychology building basement. The study was planned for two weeks. What Happened: Within days, guards became increasingly cruel and authoritarian, while prisoners became passive and depressed. Guards forced prisoners to do pushups, refused bathroom privileges, and psychologically tormented them. Several prisoners experienced emotional breakdowns. Early Termination: Zimbardo ended the experiment after six days when graduate student Christina Maslach expressed horror at the conditions. Key Findings: The experiment showed how powerful situations and roles could override individual personalities. Good people could do evil things in toxic environments. Criticisms: Later analysis questioned whether participants were play-acting based on stereotypes rather than genuinely transformed by roles. Some argue demand characteristics influenced behavior. Impact: The study influenced prison reform discussions and understanding of abuse in institutional settings like Abu Ghraib. It highlights the importance of oversight and accountability in positions of power.

Pavlov's Classical Conditioning (1890s-1900s)

Ivan Pavlov's work with dogs established fundamental principles of learning that apply across species.

Discovery: While studying digestion, Pavlov noticed dogs salivated before food arrived, anticipating meals based on environmental cues. The Process: Pavlov systematically paired a neutral stimulus (bell) with food (unconditioned stimulus) that naturally caused salivation (unconditioned response). Eventually, the bell alone triggered salivation (conditioned response). Key Principles: - Acquisition: Learning the association - Extinction: Weakening of response when conditioning stops - Generalization: Responding to similar stimuli - Discrimination: Distinguishing between stimuli Applications: Classical conditioning explains: - Phobia development and treatment - Advertising strategies - Drug tolerance and addiction - Taste aversions - Emotional responses to music or smells Legacy: Pavlov's work launched behaviorism and scientific study of learning, influencing education, therapy, and understanding of human behavior.

The Little Albert Experiment (1920)

John Watson and Rosalie Rayner demonstrated that emotions could be classically conditioned in humans.

Procedure: Nine-month-old "Little Albert" was exposed to various stimuli including a white rat, which initially caused no fear. Researchers then made loud noises (striking a steel bar) whenever Albert touched the rat, causing fear. Eventually, Albert feared the rat without the noise. Generalization: Albert's fear generalized to similar objects: rabbits, fur coats, and even Santa Claus masks. Ethical Issues: Albert's mother removed him from the study before deconditioning could occur. The identity of "Albert" and his later life remained mysterious until recent investigations. Significance: Demonstrated that phobias could be learned through conditioning, revolutionizing understanding of anxiety disorders and leading to behavioral therapies.

Harlow's Attachment Studies (1950s-1960s)

Harry Harlow's controversial monkey experiments transformed understanding of love and attachment.

The Setup: Baby rhesus monkeys were separated from mothers and given two surrogate "mothers"—one made of wire with a feeding bottle, another covered in soft cloth without food. Findings: Monkeys spent most time with the cloth mother, visiting the wire mother only to feed. When frightened, they ran to the cloth mother for comfort. Implications: Challenged the prevailing belief that attachment was based on feeding. Showed that comfort and contact were crucial for emotional development. Long-term Effects: Isolated monkeys showed severe social and emotional problems, unable to interact normally with other monkeys or care for their own offspring. Impact: Influenced childcare practices, emphasizing the importance of physical contact and emotional warmth. Led to changes in orphanage and hospital policies allowing more parent-child contact. Ethical Legacy: The severe harm to animals sparked debate about research ethics and contributed to stricter animal welfare guidelines.

The Bobo Doll Experiment (1961)

Albert Bandura's study demonstrated observational learning and challenged pure behaviorism.

Method: Children watched adults interact with an inflatable Bobo doll. Some saw aggressive behavior (hitting, kicking), others saw non-aggressive play, and a control group saw no model. Results: Children who observed aggression were much more likely to act aggressively toward the doll, often imitating specific behaviors they'd seen. They even created new aggressive acts. Gender Effects: Boys showed more physical aggression overall, but both genders imitated same-sex models more closely. Significance: Proved that learning could occur without direct reinforcement, simply through observation. This social learning theory explained how children acquire behaviors, language, and social norms. Modern Relevance: Informs debates about media violence, role models, and how children learn from their environment.

Asch's Conformity Experiments (1951)

Solomon Asch revealed the powerful pressure to conform to group opinions.

The Task: Participants judged which of three lines matched a reference line—an obviously easy task. The Twist: Participants were placed with confederates who gave clearly wrong answers. The real participant answered after hearing others' responses. Results: About 75% of participants conformed at least once, giving obviously wrong answers to match the group. Overall, participants conformed on about one-third of critical trials. Factors Affecting Conformity: - Group size (peaked at 3-4 confederates) - Unanimity (one dissenter dramatically reduced conformity) - Task difficulty - Cultural background Implications: Demonstrated the power of social pressure and the difficulty of maintaining independence against group consensus. Relevant to jury decisions, peer pressure, and social media behavior.

The Marshmallow Test (1960s-1970s)

Walter Mischel's delay of gratification studies explored self-control in children.

Procedure: Children chose between one marshmallow immediately or two if they waited 15 minutes while the researcher left the room. Hidden cameras recorded their strategies. Strategies: Successful children distracted themselves by covering eyes, singing, or pretending the marshmallow was a cloud. Follow-up Studies: Children who waited longer showed better outcomes years later: - Higher SAT scores - Better social skills - Lower substance abuse - Better stress management Controversy: Recent replications suggest socioeconomic factors play a larger role than originally thought. Trust in adults and previous experiences with delayed rewards affect performance. Applications: Insights about self-control inform education, parenting, and understanding of decision-making across the lifespan.

Rosenhan's "On Being Sane in Insane Places" (1973)

David Rosenhan's study questioned psychiatric diagnosis reliability.

The Experiment: Eight mentally healthy "pseudopatients" presented themselves at psychiatric hospitals claiming to hear voices saying "empty," "hollow," and "thud." After admission, they acted normally and reported no more symptoms. Results: All were admitted (seven with schizophrenia diagnosis), and none were detected as imposters by staff. Average stay was 19 days. Real patients sometimes recognized them as fakes. Second Study: Rosenhan told a hospital that pseudopatients would attempt admission. Of 193 new patients, staff identified 41 as likely fakes—but Rosenhan had sent none. Impact: Exposed problems with psychiatric diagnosis and institutional dehumanization. Contributed to diagnostic manual reforms and deinstitutionalization movement. Criticisms: Some argue the deception was unfair and that diagnosis has improved significantly since then.

The Bystander Effect Studies (1968)

Following Kitty Genovese's murder, Darley and Latané studied why people don't help in emergencies.

Experiments: Participants experienced staged emergencies (seizures, smoke-filled rooms) either alone or with others present. Key Finding: The more people present, the less likely individuals were to help—contrary to intuition. Explanations: - Diffusion of responsibility: Assuming others will help - Pluralistic ignorance: Looking to others for cues - Evaluation apprehension: Fear of embarrassing oneself Applications: Understanding bystander behavior has improved emergency training, encouraging specific individuals to take action and teaching people to overcome bystander paralysis.

Cognitive Dissonance Experiments (1959)

Leon Festinger's studies revealed how we rationalize conflicting beliefs and behaviors.

The Boring Task Study: Participants did incredibly boring tasks, then were paid either $1 or $20 to tell the next participant it was interesting. Surprising Result: Those paid $1 rated the task as more enjoyable than those paid $20. With insufficient external justification ($1), people changed their internal attitudes to reduce dissonance. Implications: Explains why people defend bad decisions, why hazing increases group loyalty, and how attitudes change after behavior changes.

Modern Ethical Standards

These famous experiments led to crucial ethical guidelines:

Institutional Review Boards: All research must be approved Informed Consent: Participants must understand risks Right to Withdraw: Participants can quit anytime Debriefing: Full explanation after participation Minimal Harm: Benefits must outweigh risks Special Protections: For vulnerable populations

Lessons Learned

These experiments teach us: 1. The power of situations over personality 2. The importance of ethical research practices 3. How scientific knowledge builds over time 4. The value of replication and questioning findings 5. The complexity of human behavior

Reflection Questions

1. Which experiment surprised you most and why? 2. How do these findings apply to modern situations like social media behavior or workplace dynamics? 3. What ethical boundaries should never be crossed in the pursuit of knowledge?