Brain Bulletin #65 - An Amazing Optical Illusion

in Brain Bulletin

Why do optical illusions work?

They work because your brain is wired to see what is essential; not what is real.

Here is an amazing optical illusion to present to your brain. I am always astounded when I see it. Look at the picture below. Which square is darker....A or B?

If you are like me then the answer seems simple and obvious. Square A. But not so fast. In reality both squares are exactly the same shade! Don't believe it? Neither did I. Take a look at the next picture.

checkershadow_illusion-1 (1).jpg

What you are viewing is Adelson's checker shadow illusion. It is an optical illusion published by Edward H. Adelson, Professor of Vision Science at MIT in 1995.

What is especially astonishing about this illusion is that even after your brain knows the squares are the same shade it still experiences them as being different!!

So what's going on here?

I always tell people in my live seminars the best definition of learning they will ever hear is that "learning is connecting new information to what you already know". That's how your brain works. It connects new information and stimuli to what you have already stored in your brain. Memories, experiences, emotions, etc.

In the illusion above we have a prior stored memory of how checker boards are "supposed to look". The are "supposed" to alternate light and dark. This checker board is different though.....but your brain can't see it because there is nothing like it in your brain to connect it to.

Also, your brain has stored memories of shadows and what they are "supposed to look like". This shadow is different though; it isn't there. The shadow just seems to be there; but it s not. Your brain fills it in based on prior stored memories.

So all in all we have a recipe for getting things wrong!

Remember....what you think, what you say, what you do it always based upon what you know. And what you know might be wrong. A wise person is always mindful of this.

For those of you who are inclined to want a technical explanation regarding why the illusion works here it is:

"The visual system needs to determine the color of objects in the world. In this case the problem is to determine the gray shade of the checks on the floor. Just measuring the light coming from a surface (the luminance) is not enough: a cast shadow will dim a surface, so that a white surface in shadow may be reflecting less light than a black surface in full light. The visual system uses several tricks to determine where the shadows are and how to compensate for them, in order to determine the shade of gray "paint" that belongs to the surface.

The first trick is based on local contrast. In shadow or not, a check that is lighter than its neighboring checks is probably lighter than average, and vice versa. In the figure, the light check in shadow is surrounded by darker checks. Thus, even though the check is physically dark, it is light when compared to its neighbors. The dark checks outside the shadow, conversely, are surrounded by lighter checks, so they look dark by comparison.

A second trick is based on the fact that shadows often have soft edges, while paint boundaries (like the checks) often have sharp edges. The visual system tends to ignore gradual changes in light level, so that it can determine the color of the surfaces without being misled by shadows. In this figure, the shadow looks like a shadow, both because it is fuzzy and because the shadow casting object is visible.

The "paintness" of the checks is aided by the form of the "X-junctions" formed by 4 abutting checks. This type of junction is usually a signal that all the edges should be interpreted as changes in surface color rather than in terms of shadows or lighting.

As with many so-called illusions, this effect really demonstrates the success rather than the failure of the visual system. The visual system is not very good at being a physical light meter, but that is not its purpose. The important task is to break the image information down into meaningful components, and thereby perceive the nature of the objects in view."

source: Wikipedia

You can use this information to literally think yourself fit: Think Yourself Fit!

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I had a busy July with 17 presentations. I did 3 Triple Your Reading seminars for MDA Corp., presented to Export Development Canada, flew to Calgary and presented a session at 1st Calgary Savings, and had lots of public seminars around Vancouver.

August is off to a good start with a keynote in Seattle, the Van Morrison concert, some holidays; and I get to keynote the AIM Language Western Canada Conference. At the end of the month I work with school teachers in Merritt, New Westminster, and Revelstoke.

I am currently reading a great new book called "Neurodiversity - Discovering the Extraordinary Gifts of Brain Differences" by Thomas Armstrong. Thomas and I spoke at the same conference recently...he is a great guy and his book is excellent.