Plainly put, a “heuristic” is a tool we use to simplify the decision-making process. For example, if you’re driving in the United Kingdom for the first time and don’t know the traffic laws, heuristics might help you correctly assume that a green light means go and a red light means stop. By applying what you already know about driving in America, you won’t have to waste hours reading up on England’s traffic laws. However, that same heuristic could prove harmful if you start driving in the right-hand lane, against traffic. Research psychologist Daniel Kahneman—Nobel Prize winner, and the subject of Michael Lewis’s article in this month’s issue, “The King of Human Error”—spent a great part of his life’s work discovering and cataloging the heuristics people use. Specifically, he concentrated on the situations where they lead us astray. By nature, heuristics are both useful and inaccurate; our minds have developed them to deal with a wide-ranging set of problems. In Kahneman’s forthcoming book, Thinking, Fast and Slow, he separates the thinking process into two types—System 1, in which efficiency comes at the cost of accuracy, and System 2, which requires a lot of focus and can sometimes prevent System 1 from making mistakes. When you’re asked what “2 + 2” equals, System 1 takes over, but when you’re asked what “17 x 24” equals, System 2 takes the reins. The questions in this quiz are designed to trigger System 1, which relies heavily on intuition to provide us with answers that we perceive to be correct. Whenever you find yourself “going with your gut,” that’s System 1—often standing in the way of rational thought. It’s no wonder that the word “heuristic” has its root in the word “eureka.” Go ahead and take this quiz, based (loosely) on Kahneman’s four decades of research; follow your gut and see just how wrong you are.

1.A town has two hospitals: one large and one small. Assuming there is an equal number of boys and girls born every year in the United States, which hospital is more likely to have close to 50 percent girls and 50 percent boys born on any given day?

A. The larger

B. The smaller

C. About the same (say, within 5 percent of each other)

2.A team of psychologists performed personality tests on 100 professionals, of which 30 were engineers and 70 were lawyers. Brief descriptions were written for each subject. The following is a sample of one of the resulting descriptions:

Jack is a 45-year-old man. He is married and has four children. He is generally conservative, careful, and ambitious. He shows no interest in political and social issues and spends most of his free time on his many hobbies, which include home carpentry, sailing, and mathematics.

What is the probability that Jack is one of the 30 engineers?

A. 10–40 percent

B. 40–60 percent

C. 60–80 percent

D. 80–100 percent

3a.How many dates did you have last month?

A. 1–3

B. 3–5

C. 0

3b.On a scale of 1 to 5, how happy are you these days (5 being the happiest)?

A. 1

B. 2

C. 3

D. 4

E. 5

4.Imagine that you decided to see a play and you paid $10 for the admission price of one ticket. As you enter the theater, you discover that you have lost the ticket. The theater keeps no record of ticket purchasers, so the ticket cannot be recovered. Would you pay $10 for another ticket to the play?

A. Yes

B. No

5a.Choose between getting $900 for sure or a 90 percent chance of getting $1,000.

A. Getting $900

B. 90 percent chance of getting $1,000

5b.Choose between losing $900 for sure or a 90 percent chance of losing $1,000.

A. Losing $900

B. 90 percent chance of losing $1,000