Job interviews: the shortest intelligence test ever

When you are hiring new people, you want to select the best available. There are all kinds of tests and services that can screen people. But if you want a really short IQ test, here is one.

CONTENTS: The test | Why is this important? | PS

Read the lines below and answer the question. Write it down. The correct answer is at the end of this article.

A bat and a ball cost 1,10 $.
The bat costs one dollar more than the ball.
How much does the ball cost?

This puzzle comes from a really interesting book: ‘Thinking, Fast and Slow’, by Daniel Kahneman, a psychologist who is known for his research on the psychology of judgement and decision-making as well as ‘behavioral economics’. And he got a Nobel Prize for that, in 2002. ‘Thinking, Fast and Slow’ is one of the best books I read in my adult life.

The book describes the two parts of our brain: the fast one and the slow one. System 1 (located in the amygdala, sometimes called the ‘lizard brain’) reacts superfast and automatically, system 2 is slower but it can make more complex computations. System 1 was/is necessary for our survival. It needs to react really fast: “lion = danger = run away”. System 2 takes more time, which makes it more accurate: “the lion is chained, no need to run”.

And this is what is happening in the riddle: your first response will be the one given by System 1. And then System 2 takes over, to give you the right answer… How long it will take somebody to give the right answer (so to suppress the answer by System 1), is an indication of his/her intelligence.

I did put this in practice a few times. And let’s say it was ‘interesting’…

So what is the answer? System 1 will say it’s 0,10 $. But then System 2 will take over and say it is 0,05 $. The bat then cost 1,05 $, which totals to 1,10$… How fast were you to get to the right answer?

Why is this important?
Our brain is something tricky. There is a big difference between System 1 and System 2. For some jobs System 1 might be very important (think security), for others a faster System 2 might be a plus (think innovation, complex business decisions). With this simple puzzle you can check how fast System 2 is.

PS: if you want a more extensive test, you might want to check NeuroColor. The latest issue of Harvard Business Review has an article on it. Based on scientific research, including brain research to test the theory, it looks for different personality traits that are linked to biological systems: the presence of dopamine/norepinephrine, serotonin, testosterone and estrogen/exytocin. Dopamine e.g. is linked to being curious, creative, mentally flexible. People with a lot of dopamine, are risk-takers, they seek novelty. Also the other biological systems are linked to personality traits. If you know which systems are present in a person, in his/her genes, and to what extent, you know how he/she will react in certain conditions. And you can put people in the position where they fit best. It sounds like it is a really good test.