OPTICAL ILLUSIONS use colour , light , and patterns to create images that can be deceptive or misleading to our brains . The information gathered by the eye is processed by the brain , creating a perception that in reality , does not match the true image . There are many types of “ colour illusions ”.
Colour Memory : when looking at an image that is consistent with a past experience of “ reality ”, your brain sees the images and colours in the same way .
The desert scenes change colour because your brain incorporated its recent history of redness on the left and greenness on the right and applied it to the desert scenes when you looked at them for the second time ... at least for a while .
Colour Relativity : Although colour is absolute , it is experienced differently depending on which colours are interacting with one another .
Here is a way of demonstrating this spectral phenomenon :
» First notice that the two desert scenes have exactly the same colour composition . The skies are both blue-white and the deserts are both yellowish .
» Now , focus on the dot between the red and green squares for 60
seconds , and then look back at the dot between the two desert scenes .
»
Above , the red squares appear pink when adjacent to the white squares . Similarly , the green squares appear darker when adjacent to the red squares . In reality , the red and green squares are exactly the same .
Above , the same shade of grey looks almost black on a bright background but almost white on a dark one .