IMO, one of the most unbelievable optical illusions....

[Logical]

The Squares marked A and B are the exact same color! The shadows make them look very different!

Most people have seen this, but for those who have not, enjoy!

[ZombieHorde]

1. I used this illusion for one of my speeches in school. nt

[sakabatou]

2. What was it about?

[ZombieHorde]

3. It was a two-part speech.

Part one was about paradoxes and the nature of organizations. Part two was about the usefulness of absurd thought.

[TrogL]

4. I didn't believe it so I took a screen shot

Dumped it into paint and dragged part of area A into B where it promptly disappeared. Did the same thing B to A.

That's just spooky.

[Logical]

6. LOL, that is the same thing I did the first time! Could not believe it! nt

[canoeist52]

5. A great brain excercise in color mixing for artists too.

Many shades of grey.

[kentauros]

7. While I have seen this before, and read the reason for why it is what it is,

my response is always: I don't get it.

So, it's just one of those mysteries of the brain's perception of the world around it that for some of us has to remain a mystery. I am in awe of how our perceptions can make it seem like two different shades. And I'll get eyestrain trying to stare it into visually equal shades

[Logical]

8. I agree with you...

Every couple of years I see this again and still don't believe it.

[Locut0s]

9. A good part of the explanation is that our senses actually suck :P...

Our eyes are FAR worse sensors than you might think or than we can now build in the lab out of silicon. The same goes for our other senses. So to make up for the rather poor quality provided by our eyes, ears and nose our brain has to play some very clever tricks to fill in the gaps and intelligently guess at what is going on out there. Most of the time these guesses are VERY good, but sometimes they can run afoul of a well designed illusion or other oddity.

[kentauros]

10. That's a good explanation.

It's when the brain experts get into it and start explaining why the brain makes these judgments (and seemingly exactly the same judgments from one person to the next) that my mind goes: I don't get it

[Locut0s]

12. Well I think the reason in this specific example is...

I think the explanation here is that the eye can't see this whole picture at the same time. The eye actually only sees small sections of anything at one time and it's the brain that builds up the image from lots and lots of little tinny pieces that the eyes "scan" over. In this case the brain says "there is a checker board with white and dark patches and there is a cylinder on it casting a shadow". The eyes also give you the relative colours of all these objects, their sized, relations to each other and more.

But it doesn't see everything in exacting detail, the brain is actually constructing a lot of this image. So when it sees the checker board it says to itself OK I know that the lighter coloured squares in the image SHOULD be of such and such a shade because they are in the shadow of the cylinder... But remember it's the brain that's constructing the image here, not the eyes really. So when you go and trick the brain and place a shade that is close to the right one but not quite right, the brain skips over this and just constructs the image as it thinks it SHOULD look, not the way it actually does. 99 times out of a 100 in the real world this would be accurate and you wouldn't have anything to worry about. In this specific case the brain has been tricked.

[olddots]

11. I have a few books about optical illusions

fascinating stuff about brain short circuits .

[hunter]

22. They are not "short circuits" they are software shortcuts.

Most of the time the shortcut works, the organism finds food, mates, and avoids early death, but sometimes these shortcuts fail.

[JimDandy]

13. Very cool! Had to turn it upside down and squint

to see that A, B and two other squares were the same color.

[Scuba]

14. That's NOT an optical illusion.

But it sure looks like one!

[magical thyme]

15. do you mean the squares themselves, or the letters in them?

Because other than the greenish round block, all I see are dark and light grey squares, and a grey A and B, which look like slightly different shades of grey but, as you commented, are the same shade but with different background shades and one in shadow. And when I squint at them, the A and B look more of a bluish gray...

[Logical]

16. The squares themselves are the exact same color. n-t

[hunter]

17. I like this one:

[Logical]

18. Yes, asking people to 'count the white dots' is fun!

[eShirl]

21. hurts to look at!

ow!

[Ron Obvious]

19. Yep...

My avatar

[Logical]

20. Nice!! n-t