The Vegetable Bowl Illusion

Some Truly Uncanny Illusions (and What
Illusions Imply about the Nature of Reality)

Is she old or young?  The rotating woman's head illusion.While we might want to say that optical illusions are only tricks, visual processing errors, they point to something very important. When our visual system makes errors and produces effects that cannot be, we become acutely aware that what we think we are seeing is a "construction" in our minds, albeit a misconstruction when we are dealing with optical illusions. We readily understand that the misconstructed image does not exist "out there," only in our minds.

So, for a moment, stay with that thought: We can see things that don't exist out there, that "aren't so." Ordinarily, when not dealing with optical illusions or visual aberrations, what we see in one moment is consistent with other experiences and understandings we have of the world. It is that consistency that enables us to say "Seeing is believing" or "I'm from Missouri; show me." We know that seeing something now is often a very good indicator of what we will experience later. We then talk about what we see as if "it is so, out there." And, indeed, ordinarily we can rely on the information we receive from our eyes. But we make a mistake if we then conclude that what we perceive "literally" exists—as we perceive it to be—"out there," outside of our minds. Surely something exists outside of us. But, just as surely, our perceptions do not (can not) exist "out there."

Warm up with These.

Let's get to the "Uncanny Illusions." But first, a little warm up. You know how it works. When they present an optical illusion, they always ask, "Which one is brighter?" or "Which one is longer, A or B?" And, of course, they are always the same brightness or the same length; it's an optical illusion. For example, in the famous Müller-Lyer Illusion reproduced here, which is longer, A or B?

The classic Muller-Lyer Illusion.

If you guessed that B is longer, then you "fell for it." They are both the same length. But, since most people have seen that illusion, it may not have been very convincing. In the following video, you will see a far stronger version of the same illusion. See if you recognize the similarity and the principles of perception it illustrates.

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OK now; don't fall for this one. Which picture of
the Leaning Tower of Pisa is taken at an angle
that suggests a greater amount of leaning?

(Illusion by Frederick Kingdom, Ali Yoonessi and Elena Gheorghiu)
Leaning Tower of Pisa Illusion by Frederick Kingdom, Ali Yoonessi and Elena Gheorghiu

The answer? They're both the same. In fact, they are the same picture of the Tower! If you doubt it, copy the picture and cut and paste the two images of the Tower so that the right one is on the left and vice versa. The result will be that the one on the right always leans more!

Now try the Cafe Wall Illusion. It's hard to believe, but the horizontal lines between the rows of black and white "bricks" are all parallel, straight, and level! Don't believe it? Click the image to see the proof.

Click the image to see
The Cafe Wall Illusion
an animated version.

Here's the Cafe Wall Building
Port 1010 building in the Docklands region of Melbourne, Australia
An actual building designed around the Cafe Wall Illusion
Move your line of vision to the right, close to the plane of the screen to see that
the floors of the Cafe Wall Building are all level and parallel. You can also
click on the image to have your point of view rotate to the same angle.

And here's a great version of the arc/size illusion:

Be Careful Now; Don't Be Tricked!

[NOTE: The following illusion has recently been promulgated widely on the Internet and so you may very well have seen it before. That's OK. The analysis is still valid and is far more mind-blowing than the illusion. But just to make sure you get to see some uncanny phenomena, as we go along in this discussion, we will present a bunch of illusions that are even weirder and harder to believe than this one.]

In the next illusion, which square is darker, A or B?

The incredible Checkerboard Shading Illusion

Remember now: We could be trying to trick you. So, maybe the square marked with an A is darker, as it appears—and obviously is ;-) And maybe we are just trying to confuse you with all this optical illusion talk, in order to make a different point altogether, for example, to demonstrate that you can be influenced to claim things that your own senses tell you are false. Thus, all this optical illusion stuff could just be misdirection in the service of making a completely different point. On the other hand, maybe the shading has been cleverly adjusted to make square A appear darker. So, look carefully. Which is it? Think it through and examine the picture carefully. When you are sure you know the answer, read on.

"A" Was Darker

So, if like us, you guessed that square A is darker, you were wrong. Once again, they are both the same shade of gray! Hard to believe, isn't it? We'd say it's nearly impossible to believe by looking at it. Indeed, it is so hard to believe that we required some proof. You could cut out two holes in a piece of cardboard, and press it up against the screen, and maybe that will convince you. But if you want a simple proof, click the link below and watch the animated version.

For even more powerful illusions, along with an animated "proof"
that the two squares are the same shade of gray, click here