Setting a rational basis for discussing illusions

I have thought about posting on illusions for a long time and I have recently come up with something. I was watching a lecture by Doug Crockford about JavaScript and he put the picture you see below up on the projector. The picture is Edward H. Adelson’s checker shadow illusion. Crockford said square “A” is exactly the same color as square “B”. I was doubtful.

Adelson Picture

So, I downloaded the picture and checked the pixel color of each square with Microsoft Paint. Easy to do, and that confirmed it. Crockford was right: my brain is definitely interpreting what it sees in light of my experience; my experience being that checker boards always have alternating colors.

This really affected me because the illusion is so persistent. Usually I can focus on an optical illusion and overcome it.

I have mulled this over a while now basically asking the question: if my mind is interpreting this picture incorrectly, what else is it interpreting incorrectly?

I would like to know how others see this picture because I have a hunch some can see it accurately depending on their level of training.

More coming up.