The Magic of Logic (5)

How to keep the interest of bright young kids

Last Wednesday I finished my second logic course, held for especially talented students at the local school. This time I had fourteen kids attending, between the ages of ten and thirteen. I was a little apprehensive, since the first course had 15 and 16-year-olds. But the younger kids were, if anything, somewhat sharper! Some had been warned by students of the first course.

It was a lot of fun doing logical puzzles with the youngsters — and they were most appreciative. In the post-course questionnaire they confirmed that my puzzles and problems were (1) not too hard; (2) they had understood everything; (3) it was a lot of fun; (4) they wanted more (i.e. they urgently want me to do a continuation next year). Also: they had, as I had instructed, given siblings, parents and friends the problems. Plus they had worked with them on the “homework” they got from me. That gave them additional enjoyment. They came back with stories on who was able to solve which puzzle, and how quickly. That is important: it added to their motivation.

One problem though is that pre-teen kids are usually not used taxing their minds for a protracted period of time. I noticed this in the first period. So I started using toys and tricks to give them breaks and keep them interested the whole time. Here are a couple I used. It worked beautifully.

This is a toy I have had for many years. It is called “Top Secret” and can be bought for around $10. The way I used it was designed to confuse the students of my logic course (and many others I have done it to): first I gave them the little metal top to do some trial spins on the table. The top will spin for a minute or two. After this I pulled out the base and said: “Now spin it on this. But you must be very careful not to touch the surface with your fingers. It is made of very special material, developed by NASA, which is ruined if the fat on your fingers gets onto it.”

A suitably nervous student then spun the top on the black base — and earned praise for doing it properly. After that I moved on to other logic problems, while watching how long it took for the first pupil in the class to suddenly say: “Hey, wait a minute. Why is it still spinning??” Indeed the top was spinning as vigorously as when it started. “Well,” I said, “you tell me.” Some of the kids started talking about the super-slick space-age surface; others thought the little nub on the centre must somehow be responsible; and after many minutes of spinning they started talking about “magnets”. What I was waiting for was the first utterance of a key word: “Battery”. And in both courses someone eventually said it.

After this I picked up the base, touching the surface with abandon. I pried off the bottom and show the students that there is indeed a battery driving the top. The toy is very cleverly constructed: just a nine-volt battery, connected to an spool through a single transistor. And I told them how the transistor keeps making the electromagnetic coil generate a magnet field each time one pole of the magnet in the top passes over it. This magnetic field drives the top. (One of the students in the latest course, a 12-year-old, could explain the physics better than me!)

It was all interesting and a lot of fun, but is it logic? That came in the next section: What exactly had I done? I had spoken about a super-smooth surface developed by NASA, for the sole purpose of leading the students down a false path. And finding that the top contained a magnet, which they did on their own, had also led them astray. The key to explaining the spinning had to be: where is the energy coming from? There is no such thing as a Perpetuum Mobile, free energy from a perpetual motion machine. There have been hundreds of attempts to demonstrate examples, but in every case it is just a clever trick.

After the top secret scam I like to confront people with another trick: I show them this picture:

Image for post
Image for post

The centre of the picture is clearly moving. Bafflement. This time I have to explain: nothing is moving — your brain is doing it. It is an optical illusion. The way your brain is wired, the heart in the middle of the picture only appears to be moving. I wrote about this my articles Tricking the Brain and The Café Wall Illusion, which explains some if this.

Before I sign off today I need to tell you the about the genesis of this moving optical illusion trick. I used to show a simple printout on paper to people, who found the illusion amazing — but were not fooled or anything. One day I showed it to my younger grandson, Hennes, five years old at the time. Hennes examined the paper carefully and said: “Can they make such thin batteries?” Which led me to construct the above illusion. You can do so as well: print out the image — the square with the heart in the middle — on high-quality glossy paper, and insert it in a solid wooden frame with a glass front. One additional piece of deception (to lead people astray): put some matches or toothpicks behind the printout to prop it up a little. That will lead people to believe that there is some mechanism behind the image causing the heart to move. Believe me: they always fall for it.

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Written by

Frederic Alois Friedel, born in 1945, science journalist, co-founder of ChessBase, studied Philosophy and Linguistics at the University of Hamburg and Oxford.

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