Here’s something so dazzling it’ll have your eyes crossed and your brain reeling … Take a look at these dots and try to count them! Yup, that’s it: just count the dots! 

Are you dazzled?

How does it work?

Of course, a good magician such as David Copperfield never reveals his secrets … but luckily we’re not good magicians so here goes!

According to our amiable optical expert (read ‘friendly professor who wears glasses’), you see those black dots on your screen because your brain is trying to make up for your poor eyesight. (That’s great coming from a man in specs!)

You see (pun intended) your eyes are not nearly as good as your brain makes you think they are. (Come again?)

The ugly truth is that the only part of your eye that can see much detail is the ‘fovea’ a small area at the back of your eyeball where the light-receiving cells are very tightly packed. Inside your eyeball, light rays are directed onto your fovea, via your lens. The rest of the retina sends your brain a rather sad, fuzzy, patchy impression of whatever it is you’re looking at. 

The brain, however, is an amazing illusionist! 

Usually it does it with such flair that you’re totally fooled and never suspect that your eyes are not actually ‘seeing’ whatever it is that your brain says is in front of you.

But in the case of the spots you have just seen, the brain gets it wrong and fills in a whole load of detail that’s not actually there!

As your eyes flick from dot to dot, each dot is seen via the super-sensitive fovea, which correctly sends the signal to the brain that the centre of the dot is whitish (not black), so before your eyes, the illusory black dots … disappear.

You can check this out by tricking your brain in return. Let your eyes blur a little. With practically nothing to work with, the brain doesn’t feel the need to invent details, and the dots stay fixed and white.


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Written and project managed by Berry Billingsley for the Department of Education