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19 September 2011

Mind Games 4: Answers

Answers 14-16

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14. Switching on

 

First, turn on switch one, and wait a few minutes. Then switch it off. Next, turn on switch two, and leave it on. Now go into the sealed room. Obviously, the bulb that is burning is connected to switch two. Now feel the other light bulbs with your hand. The one that's still warm is connected to switch one.

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15. A most unusual paragraph

The paragraph does not contain the letter ‘e’! This is indeed extremely unusual: ‘e’ is the most common letter in English and many other languages. It’s really hard to compose sentences without using ‘e’ – give it a try.

A ‘lipogram’ is a piece of text that’s been written, as a word game, without a certain letter. Amazingly, full-length lipogrammatic novels exist. In 1939, Ernest Vincent Wright wrote Gadsby: A Story of Over 50,000 Words Without Using the Letter “E”, and La Disparition is an ‘e’-less French novel written in 1969 by Georges Perec (translated as A Void).

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16. Checkershadow illusion:

 

The square marked A is in fact exactly the same shade of grey as the square marked B! (If you can't see it, try covering up the checkerboard to either side of A and B.)

How it works: To make sense of our environment, the brain needs to work out the colour of objects. Shade tends to dim colours, so our visual system compensates for this.

In this image, we apparently “see” a three-dimensional cylinder casting a soft -edged shadow over the checkerboard. So the brain assumes that square B is a lighter square that is dimmed by shade. In fact, it’s not lighter at all.

The illusion is aided by the checkerboard pattern. The brain notices how an object contrasts with the things around it. If a square is lighter than the surrounding squares, the brain reads it as an unusually light-coloured object; the same for a dark square surrounded by light ones.

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