Mind Games 4: Answers

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.

Back to Mind Games



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).

Back to Mind Games


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.

Back to Mind Games

Do you have a great brain teaser? Please send it to us; we choose the best ones to feature on Mind Games.

More Mind Games

We live in a world where facts and fiction get blurred
In times of uncertainty you need journalism you can trust. For 14 free days, you can have access to a world of in-depth analyses, investigative journalism, top opinions and a range of features. Journalism strengthens democracy. Invest in the future today. Thereafter you will be billed R75 per month. You can cancel anytime and if you cancel within 14 days you won't be billed. 
Subscribe to News24
Voting Booth
Have you entered our Health of the Nation survey?
Please select an option Oops! Something went wrong, please try again later.
27% - 9950 votes
73% - 26271 votes