Try this quick brain-teaser to test your critical thinking skills – and learn about a pernicious cognitive bias.
Let's play a game! All you need to start are these three numbers:
These numbers aren't random: they follow a secret rule. Our rule isn't constrained to just these three numbers: some number sequences - but not all - also obey it. Think you can figure out what our rule is?
You may have a hypothesis already, but (like any good scientist) you should gather some data first. Use the boxes below to try out other number sequences that you think also follow our rule. Test as many sequences as you'd like.
Are you confident that you figured it out? Tell us what you think the rule is in the box below. But be careful - you only get one guess at the rule, so be smart and try a few sequences to be sure that you've thoroughly tested your hypothesis!
Our rule was simple: each number is bigger than the one before it. That's it!
But most people come up with a more complicated (and wrong!) rule, like "the numbers must increase in intervals of 2" or "they're even numbers." Why do they get it wrong, especially since they were allowed to test their hypothesis thoroughly?
The answer is the mother of all biases: confirmation bias.
Confirmation bias emerges from our tendency to seek evidence that confirms what we already know, believe, or feel rather than equally looking for evidence that can prove us wrong. If you think the rule is that numbers must increase by 2, you'll try sequences that prove your rule (like 8, 10, 12), while ignoring those that might disprove it (like 1, 2, 3 or 14, 25, 113).
The English psychologist Peter Wason first described confirmation bias in 1960 by giving undergraduate students the same number sequence we gave you. Almost 80% of the students got the rule wrong on their first guess. But Wason was nicer than we were and let the students keep testing and guessing possible rules rather than demanding a single rule. The students who took the most guesses were the ones who only tested sequences that confirmed what they already thought the rule was. Their error was gathering confirming evidence and not searching for disproving evidence.
Why does the confirmation bias matter? After all, there are very few times you’ll be asked to give a rule for a number sequence! But think about all the times we make decisions where relying on confirming evidence may lead to costly, suboptimal outcomes:
- When debating an important topic, we look for data that backs up our view while ignoring information that goes against our beliefs.
- If we see a coworker as lazy, we tend to focus on all the times they’ve slacked off and ignore the times they’ve been an overachiever.
- When deciding the next step for a company or project, we may focus on everything that has gone right in the past and ignore evidence suggesting that our plan might fail.
Once we know that confirmation bias exists, we can consider strategies to outsmart it.
- When looking for data, try actively searching for disproving information.
- When someone presents data that contradicts your ideas, don’t reject it out of hand.
- Get in the habit of engaging with evidence that goes against your point of view. When something rubs you the wrong way, try responding with, “Interesting. I hadn’t thought that was possible!”
- When the evidence truly isn’t on your side, there's no shame in admitting it and announcing that your mind has been changed. It can be liberating to engage with new, opposing ideas. You may even get excited when a core belief is proven wrong!
Remember: success depends on making the best decision based on data, not just the decision that, because of confirmation, feels right.