Speed Traps Ahead!

The Art of Thinking Clearly - Rolf Dobelli 2014

Speed Traps Ahead!

Simple Logic

Three easy questions. Grab a pen quickly and jot down your answers in the margin. First question: In a department store, a Ping-Pong paddle and a plastic ball cost $1.10. If the paddle costs $1 more, how much is the ball? Second question: In a textile factory, five machines take exactly five minutes to make five shirts. How many minutes will it take one hundred machines to produce one hundred shirts? And, the third question: A pond has water lilies growing in it. The flowers multiply quickly, each day doubling the area they take up. If it takes forty-eight days for the pond to be completely covered with water lilies, how many days will it take for it to be half covered? Don’t read on until you have written down the answers.

For each of these questions, there is an intuitive answer—and a right one. The quick, intuitive answers come to mind first: ten cents, one hundred minutes, and twenty-four days. But these are all wrong. The solutions are: five cents, five minutes, and forty-seven days. How many did you answer correctly?

Thousands of people have taken this Cognitive Reflection Test (CRT), which professor Shane Frederick developed. So far, students at the Massachusetts Institute of Technology (MIT) in Boston have fared best. On average, they got 2.18 correct answers. Students at Princeton University came in second with an average of 1.63. Far below were students of the University of Michigan who scored an average of 0.83. However, despite these neat rankings, averages are not interesting in this case. More interesting is how those who scored highly differ from the rest.

Here’s a hint: Would you prefer a bird in the hand or two in the bush? Frederick discovered that people with low CRT results tend to prefer a bird in the hand. They play it safe. After all, something is better than nothing. Those who score at least 2 or higher usually opt for the riskier option. They prefer the gamble. This is especially true for men.

One factor that separates the groups is their ability to control their impulses. In chapter 51 on hyperbolic discounting, we covered the seductive power of “now.” Frederick put the following question to the participants: “Would you rather have $3,400 now or $3,800 in a month?” In general, people with low CRT scores favor getting the smaller amount sooner. For them, waiting poses a challenge because they are more impulsive. This also applies to purchasing decisions. In contrast, people with high CRT results usually decide to wait the extra few weeks. They muster the willpower to turn down instant gratification—and are rewarded for it later on.

Thinking is more exhausting than sensing: Rational consideration requires more willpower than simply giving in to intuition. In other words, intuitive people tend to scrutinize less. This led Harvard psychologist Amitai Shenhav and his research colleagues to investigate whether people’s CRT results correlate with their faith. Americans with a high CRT score (the study was conducted only in the United States) are often atheists, and their convictions have been reinforced over the years. Participants with low CRT results, however, tend to believe in God and “the immortality of the soul,” and often have had divine experiences. This makes sense: The more intuitively people make decisions, the less rationally they query religious beliefs.

If you are less than pleased with your CRT score and want to improve it, start by greeting even the simplest logical questions with incredulity. Not everything that seems plausible is true. Reject the easy answers that pop into your head. So, one more try: You are traveling from A to B. On the way there you drive at 100 mph and on the way back, at 50 mph. What was your average speed? 75 mph? Slow down, slow down!