The Bias Lab

An interactive exploration of Thinking, Fast and Slow by Daniel Kahneman. You are the test subject.

⚠️ Warning: This exhibit will trick you. Your own brain will betray you. That's the point.

Exhibit 01

Your Eyes Are Liars

"Not all illusions are visual. There are illusions of thought, which we call cognitive illusions."

Look at these two horizontal lines. Which one is longer?

Line A

Line B

🧠 They're identical.

This is the Müller-Lyer illusion. Both lines are exactly 150px. Even now that you know, Line B still looks longer. This is the key insight: you cannot unsee it.

Kahneman writes: "You have chosen to believe the measurement, but you cannot prevent System 1 from doing its thing."

This is the difference between System 1 (fast, automatic — what you see) and System 2 (slow, deliberate — what you know). Your brain has two operating modes, and they often disagree.

Exhibit 02

The Lazy Controller

"The bat-and-ball problem is the simplest puzzle in the world. Most people get it wrong."

A bat and a ball together cost $1.10.
The bat costs $1.00 more than the ball.
How much does the ball cost?

Exhibit 03

The Anchor Trap

"People who are exposed to a random number will be influenced by it when they estimate an uncertain quantity."

First, a quick warm-up. Here's a random number:

Now answer this: What percentage of countries in the United Nations are in Africa?

50%

Exhibit 04

Linda the Bank Teller

"The most coherent stories are not necessarily the most probable, but they are plausible."

Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and participated in anti-nuclear demonstrations.

Which is more probable?

Exhibit 05

The Frame Game

"Our preferences are about framed problems, and our moral intuitions are about descriptions, not about substance."

An unusual disease is expected to kill 600 people. Two programs have been proposed:

Exhibit 06

Losses Loom Larger

"The response to losses is stronger than the response to corresponding gains. This is loss aversion."

You're offered a coin flip. Tails, you lose $100. How much would you need to win on heads to accept this bet?

Win $150

Exhibit 07

The Planning Fallacy

"The prevalent tendency to underweight or ignore distributional information is perhaps the major source of error in forecasting."

Quick estimation challenge. Without calculating, estimate this in 5 seconds:

Your Results

The Bias Scorecard

"We can be blind to the obvious, and we are also blind to our blindness."

Here's how your System 1 performed across the exhibits:

Kahneman's core lesson: "The best we can do is a compromise: learn to recognize situations in which mistakes are likely and try harder to avoid significant mistakes when the stakes are high."

You can't turn off System 1. But now you know it's there.