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This is more or less on the BBC World Service.

And this week we'll be devoting the entire program to an interview with the

Nobel Prize winner in economics, Daniel Kahneman.

I will tell you about a study in which two taxi companies operate.

And one of the companies has operates green cars and the other operates blue cars.

This is more or less, I'm Tim Halford and you're listening to Daniel Kahneman,

a psychologist who won the Nobel Prize for Economics.

85% of the cars are green and 15% are blue.

Another was a hidden run accident at night, clearly involved a taxi.

And there was a witness who thought that the car was blue belong to the minority company.

And they tested the accuracy of the witness and they found that under similar

conditions when you show the witness an equal number of cabs,

the witness was accurate 80% of the time.

Now what is your probability that the cab in question was blue?

As the witness said, when blue is the minority company.

Now most people say 80% this is the common answer.

Well, here is a slight variation on this.

And you will see how different it is.

There are two taxi companies in the city, a green and the blue,

...