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Classroom Optical Illusions - Post your links!

phyz

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phyz
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Jan 20, 2004
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The Skepticism in the Classroom thread wandered into the territory of optical illusions. I'm sure there are other threads that deal with this, but it's a topic worthy of a periodic refresh.

A whole class of excellent optical illusions rely on receptor fatigue.

Articulett points us to a Jerry Andrus fave:
http://www.grand-illusions.com/pinwheel.htm

She also has a special fondness for the Spanish Castle:
http://www.johnsadowski.com/big_spanish_castle.php
You might be her new best friend if you can figure out a way to download that one for her.

A physics-teaching colleague developed a schtick around this gem from the Exploratorium. I use it to great effect every year. I call it "Physics is Mind-Expanding," but you could replace the term "physics" with something of your choosing. Depth Spinner:
http://www.exploratorium.edu/snacks/depth_spinner.html

A recent fave was presented at TAM last year. It's been on the 'net for a while, but it still blows me away each time I do it. The author of this page has some nice notes, too. The Lilac Chaser:
http://www.michaelbach.de/ot/col_lilacChaser/index.html

Chromo-wackiness.
RecoveringYuppy sends in this one that drives your eyes crazy with color, contrast, and geometry.
http://www.cs.toronto.edu/~moraes/illusion.html

There are many more out there. What are your favorites?
 
Thanks, Glenn; I knew someone out there would have collected a treasure trove of illusions and neatly posted them to one site. And I knew someone here would know where it was!
 
ViPerLab--Visual Perception Library
Viperlib is a web-based resource library of images and presentation material illuminating the study of visual perception.

All images are given freely by the vision research community and are available for educational, non-profit use only.

By using this site, you agree to the conditions of use.
Click to expand...
Great illusions--most with explanations--and slides on anatomy of the visual system, color perception, depth perception, etc...
 
And if you want something really strange http://www.sciam.com/article.cfm?chanID=sa017&articleID=000B5245-6805-128A-A3C683414B7F0000

Pretend you are a member of an audience watching several people dribbling and passing a basketball among themselves. Your job is to count the number of times each player makes a pass to another person during a 60-second period. You find you need to concentrate, because the ball is flying so quickly. Then, someone dressed in a gorilla suit ambles across the floor (right). He walks through the players, turns to face the viewers, thumps his chest and leaves. Astonishingly, as Daniel J. Simons, now at the University of Illinois, and Christopher F. Chabris of Harvard University learned when they conducted this study, 50 percent of people fail to notice the gorilla.
Click to expand...
 
The Spanish Castle one wowed me. Of course, life itself is an optical illusion.

On your retinas, the world is upside down and you have a largish blind spot in each eye, but you don't see that. In the case of my eyes, the image on my retinas is at a different angle for each eye (a shallow V), a legacy of my last eye operation. However, after a week, it was straight again. I do wear glasses, but it's my brain that corrected the angled image.
 
As an undergraduate Psychology student I was a volunteer subject for one of our professor's vision experiments. I was required to wear goggles that turned my vision upside down for several days. At one point I woke to find my vision upside down without the goggles. When I put them on again, my vision was correct. It took about 12 hours without the goggles to get back to normal. Quite a disconcerting experience, I can assure you.
 
BayAreaGuy said:
As an undergraduate Psychology student I was a volunteer subject for one of our professor's vision experiments. I was required to wear goggles that turned my vision upside down for several days. At one point I woke to find my vision upside down without the goggles. When I put them on again, my vision was correct. It took about 12 hours without the goggles to get back to normal. Quite a disconcerting experience, I can assure you.
Click to expand...

Have you written about this somewhere? Are your data included in a published article, for instance? Collected on a website?

I have done prism goggle demos for my classes, but none so elaborate as this.
 
Me too. But sources, Stratton(1896) or Pronko(1956) never showed an aftereffect lasting more than one hour.
My father was an optician and donated inverting prisms to Laurie Gulick, my sensation and perception professor. We never got the aftereffect.
I don't' believe it lasting 12 hours, maybe a false memory?
 
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I have always thought this one to be impressive. What do you see?

A youngster sees something entirely different.
A child will see dolphins. The erotic image is invisible to them.
 
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