2, 4, 8


A few weeks ago I ran across a very simple puzzle. It is a rule based on a sequence of three numbers. Some sequences obey the rule – and some do not. The challenge is to guess what the rule is. According to the opening paragraph of the article accompanying the test, the test sheds light on government policy, corporate America and why no one likes to be wrong.

The puzzle starts with the following:

2, 4, 8 – obey the rule.

Then it is up to you to provide other sequences and guess the rule.

Here is the link:


Go ahead.

Give it a try.

I won’t spoil it for you.

Once you’ve given it a try, return here.

I’ll wait.

(Jeopardy music.)

What did you think? Did you guess correctly?

The test explores confirmation bias. Were you willing to search for a “No” answer, or did your couch your guesses to give “Yes” answers? In my case, I started with a specific sequence that gave “Yes’s”: A x B = C, and tried a few others that all led to “Yes” as well.

I wondered: are there any sequences that give “No?”  So, I took a stab until I got a “No.”

The first “No” answer taught me more than all the “Yes’s” I got before. I kept trying to get “No’s.” In the end, I got 5 “Yes’s” and 7 “No’s”, at which time I decided upon an answer: each number in the sequence is greater than the number before it.

The first lesson I took away is that this test applies to more problems than those dealing with numbers.   The basic principle is applicable to many situations we face every day. In the weeks following the test, when I faced a situation and thought I knew the answer, I said to myself, “2, 4, 8.” It’s my self-cue to ask another question.

Another key takeaway: the best questions are those in which I get the opposite of what I was expecting. Such an answer shakes up confirmation bias and tells me something new.

2, 4, 8 – a simple yet powerful test to challenge confirmation bias.

2, 4, 8