Stop me if you’ve heard this one before…

New Scientist is running an article about intelligence where they claim that a high IQ doesn’t mean you’re smart. I agree in general, but one example they give is just silly. They cite:

Test your thinking

When researchers put the following three problems to 3400 students in the US, only 17 per cent got all three right. Can you do any better?

1) A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?

2) If it takes five machines 5 minutes to make five widgets, how long would it take 100 machines to make 100 widgets?

3) In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of it?

I can believe that only a small percentage of students got all three right, but I wonder what the researchers thought they proved. The above three questions are the puzzle equivalent of knock-knock jokes: if you are at all interested in word puzzles, you learned these somewhere around the fifth grade.

This reminds me of a job interview I once had, where the interviewer decided to ask me an interview puzzle. I think he started with the doorway choice: you have two doors to choose from, one leading to certain death, and two robots (or brothers, or villagers…) to help you, one of which always tells the truth, one of which always lies. What one question can you ask to make the decision. I told him I already knew the puzzle. So he asked me another, about timing 45 minutes with two ropes that will each burn in an hour. I knew that one as well. So he asked me another. And another. And another. He wouldn’t give up, but he apparently didn’t know any puzzles that I didn’t know. Eventually I asked him if it was alright for me to bring up a puzzle I had recently been working on and describe how I had solved it. He agreed and we moved on. (I got the job)

The problem in both cases is that to anyone who has an interest, the problems aren’t problems at all, and they do nothing to test the individual’s actual ability, but only their level of interest in the field of puzzles and ability to recall old chestnuts; while to anyone who has no interest, obviously they will underperform because they have no interest. If the researchers thought they were testing for intelligence by asking those three tired puzzles, they were sorely mistaken. They were really testing for a general interest in puzzles.

But perhaps an interest in puzzles correlates with intelligence. I’d certainly like to think so 😉

I’m curious how many people reading this were familiar with the above three puzzles.


2 thoughts on “Stop me if you’ve heard this one before…

  1. Katrina

    I’ve thought about this particular subject quite a bit, and enjoyed the NewScientist article, and am now thinking of subscribing. Tenatively, I think the recipe for “good thinking” as opposed to raw intelligence includes: curiosity, (which develops into interest), focus and tenacity. Many people are capable of thinking well, but have not developed it as a skill. I think every High School student should be taught about cognitive biases, etc.


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