Do you see the word LIFT?
At first, most people just see blocks of black and white. Then suddenly they see the word lift.
Everything you see is your brain’s best guess. Once you have made sense of this image it is impossible not to see it again. This is because once your brain has interpreted this image as a word, your brain will always favour this hypothesis.
It’s impossible – as soon as you focus on the black dots, they disappear!
Your eye and brain have very special mechanisms for seeing edges clearly. This allows you to see a sharp boundary between an object (e.g. a person or a building) and the background.
Your mechanism for sharpening edges is called lateral inhibition. It works by the light-sensitive receptors in your eye switching their neighboring receptors off. This makes an edge look more pronounced.
Scientists do not understand exactly why you see the black dots, but they think it has something to do with lateral inhibition.
Most people see a triangle in front of three circles.
Your brain tries to make sense of this pattern by going for the most likely explanation. In this case it is a white triangle in front of 3 coloured circles.
Even when you know that the white triangle does not really exist, your brain still opts for it as the most likely explanation.
As seen on www.youramazingbrain.org.uk