Crowds and Madness

When Groups Think Wrong

Thinking Traps Series - Lesson 4

The Wisdom - and Madness - of Crowds

In 1906, the statistician Francis Galton visited a county fair where villagers were guessing the weight of an ox. Nearly 800 people submitted guesses. Most were wildly wrong.

But when Galton averaged all 800 guesses, something remarkable happened.

1,197 lbs The crowd's average guess. The ox actually weighed 1,198 lbs. Eight hundred mostly-wrong individuals produced an almost perfect collective answer.
Source: Francis Galton, "Vox Populi," Nature (1907)

This is the "wisdom of crowds" - the idea that groups can be smarter than individuals. Markets use this. Democracies depend on it. Google's search algorithm is built on it.

But there's a dark side.

Charles Mackay, 1841: "Men, it has been well said, think in herds; it will be seen that they go mad in herds, while they only recover their senses slowly, one by one."

When individuals influence each other - when they see what others are thinking before deciding - the crowd can become spectacularly, catastrophically wrong. Stock bubbles. Mass panics. Political delusions. The same mechanism that makes crowds wise can make them insane.

75% In the famous Asch conformity experiments, 75% of participants gave an obviously wrong answer at least once - simply because everyone else did.
Source: Solomon Asch, "Opinions and Social Pressure" (1955)
Have you ever believed something mainly because everyone around you seemed to believe it? What happened when you questioned it?

The Conformity Experiment

Before we look at the research, try this quick test. Answer instinctively - don't overthink it.

The Line Test

Look at the reference line on the left. Which line on the right - A, B, or C - is the same length?

Reference
A
B
C

What Happened in the Real Experiments

Solomon Asch, 1950s

Asch put one real participant in a room with 5-7 actors who had been instructed to give obviously wrong answers. The lines were not ambiguous - the correct answer was clear.

The results were disturbing:

  • 75% of participants conformed at least once
  • 32% conformed on the majority of trials
  • Only 25% never conformed at all

When interviewed afterward, many participants said they knew the answer was wrong but felt unable to disagree publicly. Others actually began to doubt their own perception.

The critical finding: If even ONE other person gave the correct answer, conformity dropped by 80%. A single ally is enough to break the spell. But standing completely alone? Almost nobody can do it consistently.

Tulip Fever: Anatomy of a Bubble

The year is 1636. The place is Holland. The object of desire is... a flower.

1593

The Exotic Arrival

Tulips arrive in Holland from the Ottoman Empire. They're rare, beautiful, and exotic - a status symbol for the wealthy. A single bulb costs as much as a skilled worker's annual salary.

1634

The Speculation Begins

People notice that tulip prices have been rising steadily for years. Merchants begin buying bulbs not to plant, but to resell. "Everyone is making money," they say. "It would be foolish not to join."

1636

The Mania

Now everyone is trading tulips - nobles, farmers, chimney sweeps, maids. People sell their houses, their businesses, their life savings to buy bulbs. New investors see prices doubling every month. Surely this will continue forever?

1 Semper Augustus bulb = 12 acres of land
January 1637

The Peak

A single Viceroy tulip bulb sells for 2,500 florins - enough to buy a house in Amsterdam, a carriage, two horses, and have money left over. A skilled worker earns about 150 florins per year.

Peak price: 10x annual income for one bulb
February 1637

The Collapse

At an auction in Haarlem, nobody bids. Suddenly, everyone wants to sell. Within weeks, prices fall by 99%. Fortunes evaporate. Contracts become worthless. The "greater fool" stops coming.

Crash: -99% in weeks
Aftermath

The Reckoning

Courts refuse to enforce tulip contracts, calling them gambling debts. An entire generation learns that "everyone is buying" is not a reason to buy. Until the next time.

The mechanism: Each person bought because others were buying. Each person's purchase pushed prices higher, which convinced more people to buy. This is an information cascade - where people stop thinking independently and simply follow the crowd. The crowd's behaviour becomes the only information that matters.
At what point in this timeline would you have sold? Be honest - if you'd bought in 1635 and watched your investment triple, would you have sold before February 1637?

Spot the Bubble

Here's the uncomfortable truth: bubbles are only obvious in hindsight. At the time, they look exactly like legitimate growth.

The Challenge

Below are four price charts. Three show real, sustainable growth. One is a bubble that crashed. Can you identify the bubble?

Chart A
Chart B
Chart C
Chart D

The Trick Question

All four charts are bubbles.

  • Chart A: Bitcoin, 2017 (crashed 84%)
  • Chart B: Nasdaq, 1999 (crashed 78%)
  • Chart C: Japanese stocks, 1989 (crashed 80%)
  • Chart D: US housing, 2006 (crashed 33%)

The point isn't that you should have spotted them - it's that you can't spot them from the chart alone. Every bubble looks like growth until it doesn't. The people buying at the peak had the same charts you just saw.

The lesson: If you can't tell a bubble from legitimate growth by looking at the chart, what CAN you look for? Warning signs include: everyone talking about it, people borrowing to invest, "this time is different" explanations, and prices disconnected from underlying value.

The Mechanics: How Crowds Go Wrong

Individual thinking errors (Lesson 1) become amplified when groups interact. Here's how.

Information Cascades

When following others becomes "rational"

Imagine you're deciding between two restaurants. You have a slight preference for Restaurant A based on reviews you read.

You arrive and see 50 people queuing outside Restaurant B. Zero outside A.

What do you do?

Most people join the queue at B. And here's the thing - this is rational. Those 50 people probably know something you don't. Their collective choice is information.

The problem: what if the first few people in that queue also ignored their own information and followed earlier people? The cascade builds on nothing. Everyone is following everyone else, and nobody is using their own judgment.

The danger: Cascades can be started by random early choices. Once started, they're self-reinforcing. And they can be completely wrong - everyone following a trail that leads off a cliff.

Groupthink

When agreement becomes the goal

In 1961, President Kennedy approved the Bay of Pigs invasion - a plan so flawed that it's now a textbook example of strategic failure. Afterward, Kennedy asked: "How could we have been so stupid?"

The answer: groupthink. His advisors - brilliant individuals - had stopped challenging each other. Warning signs were ignored. Dissent felt disloyal. The pressure to agree overwhelmed the pressure to be right.

Symptoms of groupthink:

  • Illusion of invulnerability ("We can't fail")
  • Self-censorship ("I'll keep my doubts to myself")
  • Pressure on dissenters ("Are you not a team player?")
  • Illusion of unanimity (silence = agreement)
The cure: Kennedy later appointed a "devil's advocate" for every major decision - someone whose job was to argue against the consensus. Healthy groups need structured disagreement.

The Bystander Effect

When everyone waits for someone else

In 1964, Kitty Genovese was attacked outside her New York apartment. According to reports, 38 neighbours heard her screams. Nobody called the police.

The original story was exaggerated, but the phenomenon is real. When others are present, individuals feel less responsible to act. "Someone else will do it."

Why it happens:

  • Diffusion of responsibility: "It's not specifically MY problem"
  • Social proof: "Nobody else is reacting, so maybe it's not serious"
  • Fear of embarrassment: "What if I'm wrong and overreact?"
The solution: Point at a specific person. "You in the blue shirt - call an ambulance." Direct responsibility works; diffuse responsibility paralyzes.

The Language of Collective Thinking

Vocabulary for discussing how groups influence individuals - for better and worse.

herd mentality / herd behaviour
The tendency to follow the crowd without independent analysis - doing something because others are doing it.
The sell-off was pure herd mentality - once a few big investors panicked, everyone followed.
an information cascade
When people ignore their own information and follow others' actions, creating a chain reaction that can be based on very little actual knowledge.
The positive reviews triggered an information cascade - everyone assumed the restaurant must be good because others said so.
groupthink
When the desire for harmony or conformity in a group results in irrational or dysfunctional decision-making - dissent is suppressed.
The board suffered from groupthink - nobody wanted to be the one to challenge the CEO's plan.
social proof
Using others' behaviour as evidence for what is correct or desirable - "if everyone is doing it, it must be right."
The "bestseller" label is pure social proof - we assume popular books are good books.
to conform / conformity
To adjust your behaviour or opinions to match those of a group, often against your own judgment.
She conformed to the team's consensus even though she privately disagreed with the strategy.
an echo chamber
An environment where you only encounter opinions similar to your own - beliefs are amplified and alternatives excluded.
Social media algorithms create echo chambers - you only see content that confirms what you already believe.
a bubble (economic/social)
A situation where prices or beliefs become inflated far beyond reality, sustained only by collective belief - until they suddenly collapse.
Everyone could see it was a bubble in hindsight, but at the time, the growth seemed justified.
the greater fool theory
The belief that you can profit from an overpriced asset by selling it to someone even more foolish - the basis of all bubbles.
He knew the stock was overvalued but bought anyway, relying on the greater fool theory. Eventually, he was the fool.

Your Turn

Choose 2-3 topics for discussion. Try to use the vocabulary naturally.

1

Your Conformity Moments

Think of a time when you went along with a group even though you privately disagreed. What stopped you from speaking up? Would you do the same thing today?

2

Echo Chambers Online

How do social media algorithms create echo chambers? Is this dangerous for democracy and society? What, if anything, should be done about it?

3

When Following Is Smart

Herd behaviour isn't always wrong - sometimes the crowd really does know best. How do you tell the difference between wise crowds and mad ones? What are the warning signs?

4

Workplace Groupthink

Have you ever experienced groupthink in a professional setting - where disagreement was discouraged and bad decisions resulted? How could it have been prevented?

5

Modern Bubbles

What do you think might be a "bubble" today - something widely believed or valued that will look obviously wrong in ten years? Why do you think so?

6

The Courage to Dissent

In the Asch experiments, one ally was enough to break conformity. Who plays this role in your life - the person who gives you courage to disagree? Do you play this role for others?

Deep Dive: Extended Speaking

Choose one challenge. Speak for the full time, developing your argument with examples.

Challenge A: The Historian

Choose a historical event where crowd psychology played a major role (a financial bubble, a political movement, a mass panic). Analyse what happened using concepts from this lesson.

Challenge B: The Defender

Argue that following the crowd is usually the RIGHT strategy. When should we trust collective wisdom over our own judgment? Build the strongest case you can.

Challenge C: The Reformer

Design a system to prevent groupthink in an organisation (a company, a government, a school). What specific mechanisms would you put in place? Why would they work?

Challenge D: The Prophet

Identify something that "everyone believes" today that you suspect may be a form of collective delusion. Make your case - be ready to defend your position against every counter-argument.

3:00

Wrap-Up

Surviving Crowd Psychology

  • 1 Ask: "What do I actually know?" - Separate your information from theirs
  • 2 Beware "everyone knows" - The most dangerous beliefs are the ones nobody questions
  • 3 Find your ally - One dissenting voice breaks the spell
  • 4 Question unanimity - Real agreement involves debate; fake agreement is silent
  • 5 Be the ally for others - Your dissent might be the permission someone else needs

The Paradox

Crowds are sometimes wise and sometimes mad - and it's hard to tell which until afterward. The skill isn't avoiding crowds entirely, but knowing when to trust them and when to think for yourself.

Useful Phrases

Questioning consensus: "Is this an information cascade?" / "What's the actual evidence, separate from what others believe?"

Breaking conformity: "I see it differently..." / "Let me play devil's advocate..."

Identifying bubbles: "This feels like greater fool territory..." / "Everyone seems to assume this will continue forever..."

This week: Notice one moment where you're tempted to follow the crowd without independent thought. Pause and ask: "What do I actually know here?"