Stare at the black dot in the centre of this picture for long enough and a black-and-white image will appear to be in full colour.
But before you break into a cold sweat and frantically start to dial the number of your local opticians, we should stress this strange effect doesn’t signify that anything is wrong with your eyesight.
It’s simply an optical illusion which exploits the cone cells – the cells responsible for colour vision – in your retina.
Staring at a false colour image for an extended period, as you do here, desensitises these cells so that when the black-and-white image of Dunstanburgh Castle reappears the retina needs to readjust, and in this intervening period the picture appears to be in full colour.
‘By staring at the dot in the middle of the screen, my brain, and if you do it your brain, is doing something remarkable. I find this absolutely fascinating,’ said Dr Helen Czerski of University College London.
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