Hey, hello, and welcome to The Rest is Science. I am Michael Stevens. And I'm Hannah Fry.

And today, I really, really want to talk about a task, a test that basically everyone fails.

I have a hunch that you won't fail this test, Hannah.

Not so sure. We'll see. We'll see. Let me give you... have a hunch that you won't fail this test, Hannah.

Not so sure.

We'll see. We'll see.

Let me give you some context first, which I shouldn't normally do because in actual

experiments where this task is given, people are just there to get their 10 bucks and go.

And I think that if you hype it up and you tell people, oh, you got to

really think about it. Oh, it's so difficult. Oh, it's such a tricky one. Then people will probably

spend more time and get it right. Okay. We could talk about all of that later, but let's just dive

right into it. This is a reasoning test, a very simple single question that involves four cards that was devised in

1966 by Peter Cathcart-Wassen. And it is basically the test when it comes to studying

the psychology of reason. If you look into the history of our scientific study of human reasoning, you basically only find this test.

The test is called the Wasson selection task, and it was developed in 1966 by Peter Cathcart-Wasson.

Now, today it has been called the most intensely researched single problem in the history of reasoning.

And my two favorite philosophers, researchers of reason, Mercier and Sperber, they call it, actually, they don't know what to call it.

This is what they say.

Is this selection task to psychology of reasoning what

the microscope has been to biology? Or is it rather, as the Rubik's Cube has been to biology?

Just kind of baffling and fun. Not adding anything really of any merit. So in Wasson's original test, only 10% of people got it

right. If you look across all the studies that have replicated that sense, you get a number

...