Can You Solve This? | Facing History & Ourselves

Can You Solve This?

In this video illustrating the Wason Rule Discovery Test, people are asked to determine the rule governing a sequence of three numbers.

Video Length



  • Social Studies


English — US


Can You Solve This?

I'm going to give you guys three numbers, a three-number sequence. And I have a rule in mind that these three numbers obey. And I want you to try to figure out what that rule is. But the way that you can get information is by proposing your own set of three numbers to which I will say yes, that follows my rule, or no, it doesn't follow my rule. And then you can propose what you think the rule is. Is that fair?


Yeah. OK. So here are the three numbers. 2, 4, 8.

2, 4, 8.

You don't need to continue the sequence. You can propose a totally different sequence, whatever you want to propose. And I will simply say yes or no, that follows my rule.

2, 4, 8. 16, 32--

16, 32, and--


Yeah. Those also follow my rule.


What's the rule? What do you think?

Multiplied by 2.

That is not my rule.


That's not my rule. But you're allowed-- if you want, propose three other numbers.

3, 6, 12.

3, 6, 12.


3, 6, 12?


Follows my rule.

10, 20, 40.

10, 20, 40.

That follows the rule.

Yeah. So multiplying by 2.

I know. I know what you're doing. And yes, it follows my rule. But no, it's not my rule.

5, 10--

10 and 20.

Follows my rule.


200, 400.

Follows my rule.

500, 1,000, 2,000.

Follows my rule.

Want me to keep going?

But do I? Just keep going. You going to tell me your rule?


Am I doing it the wrong way? Am I approaching this the wrong way?

You're totally fine.


But you're approaching it in the way most people approach it. Think strategically about this. You want information.


I have information. The point of the three numbers is to allow you to figure out what the rule is.



OK. I'm going to give you the numbers that I don't think fits a sequence and then see what you say. So I'll say 2, 4, 7.

Fits my rule.

So whatever I propose is right?

So is your rule like, you can propose any number?

So the rule is anything we say is yes?


Damn it.


But you were on the right track now. Hit me with three numbers.

3, 6, 9.

Follows my rule.

Oh, that didn't follow my rule. This is good, right?

5, 10, 15.

That follows my rule.

What-- oh. Really?


I don't believe this.

1, 2, 3.

1, 2, 3.

Follows the rule.

What about 7, 8, 9?



Yes, that follows the rule.

8, 16, 39.

Fits the rule.


But you're no closer to the rule.


I want you to get to the rule.

How about 1, 7, 13?

Follows the rule.

Why is it?

11, 12, 13.

How does this make sense?

Follows the rule.

10, 9, 8.

I don't know how to do this.

Does not follow the rule.

10, 9, 8 does not.

Oh. So is it all in ascending order?

Oh, yeah.


Up top. Yes. First ones to get it. You guys nailed it. That's the rule. That's the rule-- increasing numbers and increasing order.

Numbers in ascending order. 1, 2, 3, 4, 5, 6, 10, 15, 25, it doesn't matter.

Any numbers in ascending order.

I was inspired to make this video by the book the Black Swan by Nassim Taleb. Now, the Black Swan is a metaphor for the unknown and the unexpected. I mean in the old world, the theory was that all swans were white. So each instance of a white swan would make you think yeah, that theory is pretty good.

But the point is you can never prove a theory true. And in fact, when people found Australia, they realized that there were black swans. What was interesting for me was that everyone I spoke to came up with a rule very early on and then only proposed numbers that fit with that rule they were thinking. I was looking for you guys to propose a set of numbers that didn't follow your rule--


--and didn't follow my rule. I was looking for you guys not to try to confirm what you believe. You're always asking something where you expect the answer to be yes, right?


You're trying to get at it.


But instead, you want to get the no.

You want to get the no because that's much more informational for you than the yes. If everything is giving you a yes.

No, that is true. That is really true once you say that.

That is what's so important about the scientific method. We set out to disprove our theories. And it's when we can't disprove them that we say this must be getting at something really true about our reality.

So I think we should do that in all aspects of our lives. If you think that something is true, you should try as hard as you can to disprove it. Only then can you really get at the truth and not fool yourself.



Can You Solve This?


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Most teachers are willing to tackle the difficult topics, but we need the tools.
— Gabriela Calderon-Espinal, Bay Shore, NY