It's pitifully easy to fool your primitive lizard brain. Here's proof. This is why the market is always getting the better of you. http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html
The squares marked A and B are the same shade of gray. You make a good point. We all have access to the same charts. 9 out of 10 of us just can't see it.
(I vote change the title of this thread to "It's pitifully easy to fool your primitive lizard brain" and move it to Psychology)