Really Excellent

By cjohnson | May 3, 2006 1:22 am

Well, apologies to all concerned for taking so long to post this, but here it is. The Categorically Not! two Sundays ago was -as usual- extremely enjoyable and informative. This one was all about Illusion, in some sense, the theme being “Really?”.

categorically not! Really imageWe started out with a few opening remarks by Bob Miller, who specialises in what some might call “light art”. He’s well known for creating a large number of wonderful works using light and shadow, several of them forming the cornerstone of exhibitions in the Exploratorium in San Francisco, for example. Have a look at the “lightwalk”, linked here.

categorically not! Really imageBob did not talk much, because he wanted everyone to just play, learning from getting involved. And play they did. He’d been up all night preparing (with KC Cole’s help) various fun things for people to do (see the table in the picture above, for example). All simple, and all with a little printed explanation about what to do, and the operation of the thing they were playing with or effect they were seeing. At the left you see him far out cornersexplaining to somebody how to close one eye and move their head to get a perfect imaginary cube (that your mind has created while looking at a cutout piece of paper – a slightly distorted convex corner) to rotate eerily. The cube you see looking at the convex cutout looks a bit like one of the cubes in the image to the right. Here is the blurb that came with the illusion:

To Do and Notice:

Place your corner/cube on a table top. – Adjust the foot-flap on the back so that the “corner” stands up on its bottom edge. – Stand back about 4 feet. – Close one eye (or cover one eye with a hand) and look at the corner/cube.

The concave corner may “pop out” and appear as a convex white cube. If/when it does, just relax and enjoy the illusion.

Now move your head back and forth (or walk by the cube), or move your head up and down. The “cube” will follow your motion!

It may take a few tries. You may have to try the other eye, or adjust your distance from the cube, but with a little practice, most people experience the illusion. Make sure there are no shadows being cast into the “corner” and that the lighting is uniform.

Some people get so good at “popping out” the corner that they can learn to see it with both eyes open; in this case, it may help to be farther away.

With enough practice, you may be able to hold it in your hand and, as you rotate the “corner,” the “cube” will move in a counter-intuitive manner.

Once you’ve learned to see the cube quite easily, you may notice a subtle but distinct change in the perceived luminosity when the switch from corner to cube occurs.

What’s Going On:

Cubes are such common shapes that your mind’s eye is already perfectly primed to see them—even when they don’t exist. Using tricks of perspective, Bob designed the angles of the sides so that they help the “corner” look like a cube.
As you move your head back and forth or up and down, your eye/brain gets a new clue—one that should immediately make you realize that you’re not looking at a cube, but rather at a corner. Yet it doesn’t.
Here’s why: We’re all familiar with parallax: When you’re driving, trees in the distance barely seem to move, while roadside fence posts whiz by.
When the “corner” turns into a cube, near and far suddenly get reversed. You would think the information you get from parallax as you move your head would destroy the illusion—that is, telling you what is “really” inside and what is outside, close and far. Instead, the brain interprets the reversed parallax by “seeing” the cube follow you. It not only jumps to the wrong conclusion; it uses the new information to “see” something impossible.

So What:

As Alice learned, it’s remarkably easy to believe impossible things—especially when we want to do so. Any additional information can compound the illusion rather than destroy it. Some people believe this can explain such seemingly “impossible” things as the continuing support for George Bush that persists in the fact of one contradictory fact after another.

Heh. He stepped out a bit on the last sentence. Funny.

Below are some other attendees in action with some of the other optical games:

categorically not! Really image
Actually, that was Jeff (a regular Cosmic Variance commenter) and author, radio commenter/storyteller (e.g., This American Life) and USC professor Aimee Bender teaming up there. Below is another pair, Elizabeth Janssen on the right:

categorically not! Really image

Next up was Richard O. Brown, a staff neuroscientist at the Exploratorium.

categorically not! Really image

He presented a series of really striking images showing the power of optical illusion. Some of them were just amazing! He spoke a lot about the basics behind how the mind plays with various perceptions, making adjustments here and there to add to what the eye actually sees, sometimes making terrible mistakes. This is interesting from the point of view of simple entertainment, but also vitally important in several important aspects of everyday life and society. Two examples which come to mind are the reliabiltiy of eyewitness reports, and the danger of driving while distracted (by for example a phone conversation). The point of the latter example is the fact that there are several cases where you simply don’t perceive something at all if you are engaged in another task, even though it is right there in the frame. There’s a famous video illustrating this, whcih he showed, and which I won’t spoil by telling you about its content. He talked about and illustrated several such things, complicated ones like that video and simple ones like our perception of light and dark being so variable. As an example of the latter, he did the following. He held up a card in front of the bright beam from the projector. It looked, as you can imagine, like a very bright white piece of card. But then he put another piece of card next to it, and only then did you realize that the first was in fact a black piece of card, by seeing how much brighter a real white card -the second- was. The point is that our perceptions of light and dark can swing between remarkable extremes depending upon the nature of the objects nearby with which comparisons are made. You all know a common example of this. The moon is not white -far from it in fact- but it sure looks like it, alone in a night sky, doesn’t it?

Well, here are some links he told us about. Have a look at Project Implicit for various tests and illustrations in “Social Cognition”. For a really amazing set of visual illusions, have a look at Michael Bach’s website, and be prepared to be bowled over by how wonderful they are. Another excellent site, that of Akiyoshi Kitaoka, shows several visual illusions which produce apparent motion when you look at them. You just can’t stop it! In fact, it can be so powerful for some viewers, I won’t put any of them up here, since it can induce dizziness and sometimes nausea. So be careful. Last, but not least, look at Jeremy Hinton’s amazing illusion at this link.
Click on the illusion to make it full size and follow the instructions. That green dot that appears from nowhere and circles around is entirely constructed by your mind. It is not there. Or is it? If nobody painted the green dot, but yet your mind constructs it and gives it motion, unfailingly, what does it mean to say that it is not there? I’m not sure. Maybe it is as real as the purple dots.

Next up was writer Aimee Bender, who is well known for many a marvellous piece of writing. Turns out she’s a professor at USC in the English department, which I only realized recently!

categorically not! Really image

Aimee talked about the use of illusion in storytelling. Not neccessarily fantastical stories -in any story. There is always an element of illusion used in order ot create something real within our minds. It was wonderful how she unpacked this and explained the storytelling process. She gave a number of examples, reading some wonderful stories. I decided to email her to get a reminder of the sources she read from, but also to get a description of what she was trying to get across to us directly from her, so that I don’t get it wrong. She sent me a reply, and I can think of nothing better but to simply paste it here:

The stories I read were “The Weather in San Francisco” by Richard Brautigan and “In a Room (Butterfly)” by Barry Yourgrau, from Wearing Dad’s Head. I think I referred to Flannery O’Connor, who says you can’t separate a theme from a story, and to Walker Percy, who talked about how words become shortcuts, from an essay of his called, I think “On Naming and Being”.

Mainly I was wanting to get across the idea that in fiction, illusion is reality, and reality is illusion, and the two are working together to create something for a reader that evokes something hard to capture, hard to articulate. And in that illusion– is access to the whole range of human experience and feelings and ideas.

Aimee also set up some audience participation activity, although we were running low on time, and so I think she did not go as far with it as she would have liked. Everybody had a bit of paper and a pen and, on her command, wrote down an emotion or feeling. Then they handed it to their neighbour,who turned the piece of paper over and wrote a little description or story which illustrated that feeling. We had a few of those read out to everyone. It was an interesting exercise, in that it immediately illustrated aspects of the process of trying to create something real (the feeling) by constructing a tale (the illusion) about it. I’m sure there was more there than that too, but I’ll stop there.

I had a great time talking to Aimee afterwards, and we were both intrigued by the possibility of maybe collaborating on something in the future, as we are both at USC with interests in crossing the borders between disciplines: The Arts meet the Sciences. I have no idea what we might create, but I can sense the possibility of promising ideas taking shape just because we are on the same wavelength on a number of things. Like happened when I started chatting with my colleague the playwright Oliver Mayer – ideas sparked there too, just because we got on the same page. And we wrote a play. So we shall see.

The evening did not end with the conclusion of the presentations. No, we all went to dinner and filled up a giant table in the nearby restaurant Typhoon, like last time. I won’t attempt to describe all the excellent conversations that I could hear going on around me there. Instead I’ll end with a lovely image of Bob Miller explaining about colour mixing and imagine through a pinhole (and how even after you take away the pinhole, its effects are still there -empty space is just a infinite number of pinholes-) to a transfixed impromptu gathering after the evening’s event was over, making us all late for dinner and therefore really really hungry for more discussion, interaction, and yes, food.

categorically not! Really image

Feel free to share what you think about the links above, the event, and especialliy if you were there – feel free to fill in bits I left out.


CATEGORIZED UNDER: Academia, Arts, Science
  • Jeff Nuttall

    Hm…these Categorically Not! events sound really interesting. If they’re open to the public (as I gather from the Categorically Not! webpage they are), I think I’m going to try to get to the next one…

  • Clifford

    Jeff… that’s why I put posters up and advertise it in the department from time to time.

    See you there!


  • Plato

    You know Clifford, I am learning to see in ways that I am not use too, looking at the theotical methods you scientists like to deal with.

    But I truly find this “categorically not” most satisfying becuase of the broad range that is being implored here.

    Are not all students of theoretics schooled with the artistic ways taught in your article to see with “imagination” this way?

    I fondly think of Penrose and Escher here. Cubist art, to monte carlo methods developed in quantum gravity scenarios. Science and Art.

  • Cynthia

    Unfortunately your right: The Bush Administration is a Master of Illusion. However – speaking with “first-line” optimism, reality will supersede illusion. Speaking with “second-line” optimism, if reality does not step-in to erase illusion, then – perhaps – a higher illusion will step-in to cancel the Bush illusion.

  • Plato

    Click on name.

    If it seems confusing, it is sometimes when you mix such visualization techniques with theoretical defintions

    An example of cubist paintings in relation to quantum gravity?

    “Points,” on brane thinking?

  • Jeff Nuttall

    Jeff… that’s why I put posters up and advertise it in the department from time to time.

    See, since I’m working under Dr. Judge at the Space Sciences Center, I spend all my time at the Stauffer Hall of Science and very seldom have reason to go to the Seaver Science Center, so I haven’t seen the posters. (At least, if there are also posters up at SHS, I haven’t noticed them.) Ah, well; I know about it now, at any rate. 😉

  • Michele

    Indeed, it was a great night. The enthusiasm of the Exploratorium scientists/artists is very contagious.

    For a more whimsical and entirely more satisfying version of the “pop out” cube illusion, which works by the same principle, make yourself one of the Paper Dragons originally designed in honor of Martin Gardner (the linked URL has a downloadable PDF, and includes a video of the illusion, which evidently can also fool the camera).

    I still have one of these dragons on my desk, and seldom a week passes that I do not find myself looking intently at it for a few minutes, moving my head up and down… seeing me must make for an interesting spectacle…

  • Clifford


    It was great to meet you. Thanks for coming and thanks for commenting.


  • Jeff

    Great write up as usual Clifford. I think the thing I liked about this Cat/Not event was the interaction that was forced upon us. Getting up and walking around the room for the illusions, and writing and exchanging thoughts/words with our neighbors during Aimee’s part was great. At least one “interactive” part would be fantastic in future events, but that’s hard to plan, I know.

    For the aforementioned “famous” video that illustrated perception, illusion, and attention span, you can go to: . BUT — the critical part is that when you watch the video the first time, please carefully count how many times the white-shirted basketball players bounce the ball. It’s critical that you try to count that number correctly.

    Feel free to post here what you think you count…

  • Spatulated

    Wow, suprizingly i just blogged about about an awsome illusion i found. you guys might like it, just click my name.

    anyways, illusions are so freaking awsome. i hope to follow all of those links after i finish this paper.

    thanks for the information

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  • im

    jeff, did you like the sentence I composed using your initial word?

  • Jeff

    of course Ilaria! it’s also true you knew a lot more about what I meant with that word….

  • im

    insider tricks …but it applies to more much more then that, doesn’t it?

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