Really Weird Optical Illusion

! Warning: this post hasn't been updated in over three years and so may contain out of date information.

David Arno's Facebook profileAs you may know – assuming you use facebook yourself – there are various fun and amusing little applications available on facebook that, amongst other things, test you in various ways. I recently stumbled across one such application that tested one’s ability to see through optical illusions. Most of the illusions were fairly standard ones, but the last one really caught my attention. I’ve reproduced it below:

Optical illusion


Question: Which square is darker?

(1) Square A (2) Square B (3) Neither

The correct answer is (3) Neither. Apparently your brain compensates for the shadow and so square B appears brighter. I answered (1) as square A looks so much darker, I assumed it a trick question (a number of previous questions’ correct answers were that they were the same). So I loaded it up into a graphics program and checked the RGB values of the squares. What amazed me was that not only were they the same, the effect of the brain recolouring square B is so strong, that the square itself looked a completely different colour to that shown by the dropper tool as shown below:

Which all leads to a rather obvious conclusion: do not trust your eyes or brain to show you what is really there!