The World’s Shortest IQ Test: Can You Answer These 3 Questions Correctly?

Curious about your intelligence? The Cognitive Reflection Test (CRT), developed by psychologist Shane Frederick in 2005, is often hailed as the shortest IQ test in the world. Comprising just three deceptively simple questions, this test has a fascinating history and a surprising level of difficulty. Let's explore the details, dive into the answers, and understand what this test reveals about our thinking.

What Is the Cognitive Reflection Test?

The Cognitive Reflection Test was designed to measure an individual’s ability to override their initial intuitive responses and think critically. Despite its brevity, the test has tripped up many people, including students from prestigious universities like Yale, Harvard, and MIT. In fact, only 17% of test-takers manage to answer all three questions correctly.

This test is not about how quickly you respond but rather about the analytical depth you apply to solving problems. Each question hides a subtle trap that lures you toward an intuitive—but incorrect—answer.

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The Questions

Below are the three questions from the CRT. Take a moment to answer them before we proceed to the explanations and answers.

1. A bat and a ball cost $1.10 together. The bat costs $1 more than the ball. How much does the ball cost?
2. If 5 machines take 5 minutes to produce 5 items, how long would it take 100 machines to produce 100 items?
3. In a lake, a patch of water lilies doubles in size every day. If it takes 48 days for the patch to cover the entire lake, how long does it take to cover half the lake?

Got your answers? Let's see how you did.

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Why Do So Many People Get It Wrong?

The CRT is designed to test our ability to resist instinctive, intuitive answers and engage in reflective thinking. Many people instinctively answer:

• 10 cents for the first question.
• 100 minutes for the second question.
• 24 days for the third question.

These answers are incorrect but feel intuitively right at first glance. This demonstrates how quickly our brains jump to conclusions without fully analyzing the problem.

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The Science Behind the Test

Frederick’s study involved over 3,000 participants across 35 experiments conducted over 26 months. He found that even highly educated individuals struggled with the CRT:

• Only 48% of MIT students answered all three questions correctly.
• Many participants got just one or none correct.

The CRT highlights the importance of analytical thinking and the difficulty of suppressing automatic responses.

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The Correct Answers

1. How Much Does the Ball Cost?

Correct Answer: 5 cents.
Explanation:
If the ball costs x and the bat costs $1 more, then the bat costs x + $1. Together, they total $1.10:

$$x+(x+1)=1.10$$Simplifying:

$$2x+1=1.10$$ $$2x=0.10$$ $$x=0.05$$Thus, the ball costs 5 cents, and the bat costs $1.05, totaling $1.10.

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2. How Long for 100 Machines to Produce 100 Items?

Correct Answer: 5 minutes.
Explanation:
If 5 machines take 5 minutes to produce 5 items, then each machine produces 1 item in 5 minutes. With 100 machines working simultaneously, each machine still takes 5 minutes to produce 1 item. Therefore, all 100 machines produce 100 items in 5 minutes.

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3. How Long to Cover Half the Lake?

Correct Answer: 47 days.
Explanation:
If the patch doubles in size daily and covers the entire lake on day 48, it must have covered half the lake on day 47. This exponential growth means the size of the patch is halved each preceding day.

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How Can You Improve Your Analytical Thinking?

1. Pause Before Responding

Take a moment to reflect on whether your initial answer makes logical sense.

2. Break Down Problems

Simplify each problem into smaller parts to analyze it more thoroughly.

3. Practice Critical Thinking

Engage in puzzles, brainteasers, and other logic-based activities to strengthen your cognitive skills.

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Diagram: Exponential Growth of the Lily Patch

Here's a visual representation of how the lily patch grows over time:

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Final Thoughts

The Cognitive Reflection Test may be short, but it packs a punch in assessing our thinking abilities. It reveals how often we rely on intuition over analysis, offering valuable insights into how we approach problem-solving. Whether you aced it or not, the CRT serves as a reminder to slow down, think critically, and embrace the challenge of deeper thought.

Are you ready to test your friends? Share this test and see how they fare!