Benham’s top, named after the English toymaker Charles Benham, is a phenomenon that’s not entirely understood but pretty cool all the same.
After concentrating on the revolving image below, every person will see a different colour.
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The best theory put forward is from scientists at Washington university:
“It is possible that the colours seen in spinning Benham disks are the result of changes that occur in the retina and other parts of the visual system. For example, the spinning disks may activate neighbouring areas of the retina differently. In other words, the black and white areas of the disk stimulate different parts of the retina.”
What colour do you see?