

If you had a hard time with this, you're not alone. This is a classic left brain-right brain conflict. The right part of the brain is trying to say the colour, but the left part of the brain is trying to say the word. How do you think this affects the creation of street signs and the layout of publications like books? Are there animals in the wild that take advantage of something like this?
Take a look at the picture of the Queen below. It’s the Queen, but black and white have been switched. Stare at one point in the center of the picture of the Queen for about one minute, then look at the blank white square just to her right. In the blank square you now see a picture of the Queen, but with black and white they way they should be. When we look at the black and white picture of the Queen, the black parts don’t wear out the light receptors in our eyes, because they’re not very bright, but the white parts of the picture do start to wear out the light detectors in our eyes. Then, when we look away, we see black where our light receptors have been worn out, and the white background where the light receptors were not worn out. But don’t forget, we have black and white light receptors, as well as colour light receptors, too, so this optical illusion should work just as well with colours.

The most obvious weakness that our eyes have is that the light detectors in our eyes get tired if we use them too much. This happens when we look at something too bright, or stare at something for too long. If you’ve ever looked at something bright and then looked away, you might have noticed that you see a black spot floating in front of you that disappears after a while. This happens because the bright light really wears out our light detectors, so when we look away, those light detectors that got hit with the really bright light aren’t working as well any more, so that part of our vision is darker. We can see a similar effect if we look at something not very bright, but for a long time.