The lines that weren't hard to judge
In the early 1950s at Swarthmore College, Solomon Asch showed groups of students a card with one line and asked which of three comparison lines matched it. The task was easy: alone, people almost never made mistakes. But only one person in each group was a real participant. The others were actors who, on certain rounds, all confidently gave the same wrong answer.
Across those critical rounds, real participants went along with the obviously incorrect majority about a third of the time, and roughly three in four conformed at least once. Yet a quarter never conformed at all, and when even one actor broke ranks and gave the correct answer, conformity dropped sharply. A single ally makes it far easier to trust your own eyes.
Obedience in a Yale basement
In 1963 Stanley Milgram published results from Yale University in which volunteers were told to deliver increasingly strong "electric shocks" to a learner (an actor who received no real shocks) whenever he made mistakes. In the best-known version, 65% of participants continued to the maximum 450-volt level when an experimenter calmly insisted.
The study remains powerful, but it has been re-examined. Psychologist Gina Perry's 2012 book Behind the Shock Machine drew on Milgram's archives and found that experimenters sometimes departed from the script and that many participants doubted the shocks were real. Obedience rates also varied widely across Milgram's own variations, dropping when the experimenter gave orders by phone or when the participant had to touch the learner.
A timeline of classic studies
- 1951 · Asch conformity experiments
Group pressure leads people to deny the evidence of their own eyes on simple line judgments. - 1954 · Robbers Cave
Muzafer Sherif's summer-camp study shows rivalry between boys' groups and how shared goals reduced it. - 1957 · Cognitive dissonance
Leon Festinger describes the discomfort of holding conflicting beliefs, tested in his 1959 "$1 vs $20" study with James Carlsmith. - 1963 · Milgram obedience studies
Ordinary people follow an authority's instructions further than anyone predicted. - 1968 · Bystander effect
John Darley and Bibb Latané show that people are slower to help when they believe others are also present. - 1971 · Stanford Prison Experiment
Philip Zimbardo's role-play study, later heavily criticised for coaching guards and lacking controls. - 1984 · Influence
Robert Cialdini's book outlines principles of persuasion including reciprocity, social proof and scarcity.
Why crowds help less
The bystander research was sparked by the 1964 murder of Kitty Genovese in New York, reported at the time as having been ignored by 38 witnesses. Later investigations showed that account was badly exaggerated: fewer people saw the attack, and some did call for help. But the lab findings held. In Darley and Latané's 1968 study, participants who believed they were the only one hearing someone have a seizure over an intercom helped quickly; those who believed four others could hear were much slower. Responsibility gets diluted across a crowd.
The encouraging twist: a 2019 analysis of real CCTV footage from public conflicts in Lancaster, Amsterdam and Cape Town, led by Richard Philpot, found that someone intervened in about nine out of ten incidents. Crowds diffuse responsibility, but they also contain more potential helpers.
Research check: Thibault Le Texier's 2018 archival work and later interviews revealed that Stanford Prison "guards" were encouraged to be tough. Most psychologists now treat the study as a demonstration, not solid evidence about human nature.
Social proof in daily life
Robert Cialdini called it social proof: when unsure, we look at what others are doing. It is why restaurants with queues attract more queues and why hotels that told guests "most people staying in this room reuse their towels" saw higher reuse than those that simply asked guests to help the environment, as Noah Goldstein, Cialdini and Vladas Griskevicius reported in 2008. The same mechanism can spread good habits as easily as bad ones. Knowing about it lets you choose your crowd more deliberately.
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