The Cognitive Reflection Test

Here’s a brain teaser for you.

Did the answer 10 cents immediately spring to mind? It certainly did for me when I first tried to solve this puzzle, and I confidently predict that 10 cents will be the answer offered by most people. However, it’s the wrong answer.

Once you realise that the difference between $1.00 and 10 cents is only 90 cents, it becomes obvious that it can’t possibly be the right answer, which is actually 5 cents.

The bat costs: $1.05

The ball costs: $0.05

The bat costs $1.00 more than the ball.

This simple but ingenious puzzle was devised by Shane Frederick as part of a 3-item Cognitive Reflection Test (CRT), which he developed as part of his research into cognitive ability.

According to Frederick, what’s needed to solve each puzzle correctly within the CRT is:

The suppression of an intuitive yet erroneous answer that springs impulsively to mind.

The reason for this instinctive but often misguided train of thought was addressed by the late, great Nobel Prize-winning psychologist Daniel Kahneman in his bestselling book Thinking, Fast and Slow. The book is divided into two parts, which correspond to the two systems of thought that Kahneman identified as System 1 and System 2.

System 1 is the fast, automatic, and unconscious system of thought that is responsible for our gut reactions and intuitive judgments. It’s quick and efficient, but it’s also prone to biases and errors.

System 2 is the slower, more deliberate, and conscious system of thought that is responsible for logical and analytical thinking. It’s more effortful and less prone to errors, but it’s also slower and less efficient.

With this in mind, have a go at solving the other two puzzles in the Cognitive Reflection Test:

If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?

In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?

Imagine you’re scrolling through Facebook or Instagram and see a dramatic headline that pretty much confirms something you believe. You’re not sure of the source of the claim in the headline, but it sounds plausible and has been shared and commented on lots of times.

Do you think you would bother to check whether it’s true?

Research conducted by Gordon Pennycook and David Rand found that people who performed better on the Cognitive Reflection Test were also better at distinguishing between genuine and false news headlines. This was the case even when the headlines supported their existing beliefs.

“Our findings therefore suggest that susceptibility to fake news is driven more by lazy thinking than it is by partisan bias per se – a finding that opens potential avenues for fighting fake news.”

This doesn’t mean that System 1 thinking serves no useful purpose. Without it, we would be subject to exhausting amounts of conscious thought each and every day. The problem arises when we allow system 1 thinking to go unchallenged in situations where details and accuracy matter.

A useful rule of thumb is to simply slow down whenever a decision is important, an answer comes to mind suspiciously quickly, or the thing you’re thinking about provokes a strong emotional reaction.

Before immediately accepting your initial response, ask yourself:

Does this answer make sense?

What evidence supports it?

What evidence might prove it wrong or offer a broader perspective?

A simple reminder to yourself to consider accuracy is often worth giving.

Because it provides a brilliant way of highlighting the tension between the first answer that springs to mind and the slower, more deliberate thinking needed to check whether that answer is actually correct.

System 1 thinking helps us make quick and efficient judgments, but those judgments are not always reliable. System 2 thinking gives us the opportunity to pause, question our assumptions, and take a closer look.

The key lesson isn’t that we should distrust every instinctive response.

It’s that some situations deserve more thought than we initially give them.

How did you do? Let me know in the comments.

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