The last day, the last month
Posted by Dave on May 28, 2010 | 4 Comments
It’s been a good four-month run, but I’ve decided to end my experiment with The Daily Monthly. There have been some tremendously satisfying moments in this process, but in the end, there were too many problems with the model to make it sustainable.
Originally, I was hoping that each month’s topic would evolve into a story, that each day’s post would add depth and layers of understanding to the narrative. In some ways, that worked, but I’ve never been really happy at the end of a month with what I’ve produced. Perhaps that’s because I chose topics that were so open-ended that it was difficult to come to a satisfying conclusion, but I think it has more to do with the limitations of the format.
The very title of this blog indicates that there will be something new every day, and with each month, we’ll move on to another topics. In real life, narratives don’t work that way. Some days are slow, and some days have tremendous revelations. Some topics can be covered in a month, and some can be covered in a week. Some might not be adequately addressed in a lifetime.
That said, I think there’s some neat stuff on this blog, and so I’ll try to keep it up and functioning. I’ll continue to allow commenting, spam permitting. If you haven’t checked out all the topics, I encourage you to do so. There is some compelling stuff in each month’s coverage:
In case that seems a little too overwhelming, here are some of the most-notable posts:
AIDS in America
World Population
- What does it mean to be “Overpopulated”?
- Population optimism: A global eco-techno-utopia
- What is the impact of strict population control?
Fitness
- How much does exercise affect health?
- Can my new iPad help me live longer? (update)
- A day at McDonalds vs a day on DASH
Illusions
- Spinning ellipses perplex the visual system
- Best illusion of the year 2010
- The hollow mask gets a nose ring!
At this point, I don’t have a plan for what’s next. I’ll probably take a couple months off from daily blogging, and then we’ll just have to see.
Lightness and contrast illusions help illuminate the visual system
Posted by Dave on May 25, 2010 | 3 Comments
You may not have noticed that the banner artwork for this month’s topic is itself an illusion, based on a design by Stuart Anstis:
Each diamond is identical, yet each row of diamonds appears to be darker than the row above it.
I can construct a simpler version of the illusion with just two squares:
Again, the squares are identical, but the square on the left looks darker (although this illusion isn’t as strong as the diamond illusion). Why?
The reason is that our visual system actually has to do a lot of processing to create a coherent picture of the world. In order to do it needs to make a lot of assumptions. The well-known checkershadow illusion can help you see why:
How do we know what historical figures really looked like?
Posted by Dave on May 20, 2010 | 5 Comments
Compare these two pictures of George Washington. Which one is more accurate?
Most Americans would probably guess the picture on the left. (Left-image: Gilbert Stuart “Vaughan” portrait of George Washington. Source: Wikimedia Commons. Right-image: Charles Wilson Peale portrait of George Washington. Source: Metropolitan Museum.) But how would you really know? Gilbert Stuart is a more famous portraitist than Peale, having painted the famous incomplete Athenaeum portrait of Washington. Are you just biased because you’re more familiar with Stuart’s work?
It might seem that there is no way to know—after all, there are no photographs of Washington—but Eric Altschuler and Ahmed Meleis believe they have come up with a method to assess a portrait artist’s accuracy in representing his or her subjects. While there are no photographs of the first five U.S. presidents, John Quincy Adams was photographed. He also had his portrait painted by both Stuart and Peale. Unfortunately, the photograph was taken late in Adams’ life, much later than the portraits were made. So Altshuler and Meleis used computer software to artificially “age” the portraits:
Daniel Simons interview, continued: Change Blindness
Posted by Dave on May 18, 2010 | 7 Comments
Last week I interviewed Daniel Simons for Seed Magazine. But the interview that ran there actually only included a little over half of our discussion. In addition to his work on inattentional blindness, Simons is also a leading figure in a different line of research, called change blindness.
Here’s a quick video demonstrating the phenomenon of change blindness:
It’s uncanny how difficult it can be to spot changes occurring right before our eyes. In this case, it seems impossible that anyone would miss it, but Simons and Daniel Levin found people missed this sort of change around 50 percent of the time!
Simons and Christopher Chabris’ book The Invisible Gorilla, which covers both change blindness and inattentional blindness, comes out today (Amazon, Barnes & Noble, Powell’s). I’ve read an advance copy provided by the publisher, and I highly recommend it.
Munger: You’ve studied change blindness for over 13 years. Tell me a bit about that field and your contributions.
Simons: I got into it indirectly. I was studying how kids can categorize different kinds of objects, and I was trying to see if they would notice some kinds of changes more than others. It turned out they weren’t noticing anything. Adults too. I was also studying motion picture perception with Dan Levin, and we were looking at whether people notice editing mistakes in movies. There was kind of a convergence of research on it in the early days. Ron Rensink was starting to use his flicker task, we were starting to do motion picture perception research, and most of it built on some work by George McConkey some years earlier.
The hollow mask gets a nose ring!
Posted by Dave on May 13, 2010 | 8 Comments
The hollow face mask illusion is a great three-dimensional effect that’s remarkable because it not only works in movies, it also works in real life. Check this out:
This is a computer-generated image (from the Max-Planck-Institut für biologische Kybernetik in Tübingen), but it can just as easily be perceived with a real hollow mask. Here’s Thomas Papathomas’s 2008 illusion of the year, produced with a physical mask on a turntable. This works best if you sit back a bit from your computer monitor (or watch on a small display like an iPhone).
Can Kids Ken Kanizsa?
Posted by Dave on May 12, 2010 | 1 Comment
The Kanizsa Illusion is one of the best-known and simplest visual phenomena:
Most adults readily see not only the three “pac-men,” but also the triangle formed by their “mouths.” This effect can be used to create virtual rectangles, stars, and other more complicated shapes. What’s less clear is at what age children are first able to see the illusion. Some research suggests that infants are able to perceive it, but other studies find that kids as old as five or six still have difficulty recognizing the shapes suggested by the pac-men.
So a team led by Kimberly Feltner developed a test that could be administered to kids as young as three years old. They trained children ranging from age three to nine, as well as adults, in three phases: comparing shapes, comparing orientation, and finally comparing real shapes to shapes suggested by Kanizswa contours. In each case, they first saw a model shape, then chose between two choices to identify matching shapes, presented as real shapes or Kanizswa illusions depending on the training phase.
Every age group could complete the first two tasks at 80 percent accuracy, but children age three to four had difficulty with the Kanizswa task, only getting about 70 percent correct. This is still better than random guessing, so in some senses these young kids can do the task, but the researchers suspected that younger kids were taking a different approach to the problem.
Live from VSS: When you make a bad tennis shot, the ball seems faster
Posted by Dave on May 11, 2010 | 2 Comments
Pro golfers say the hole seems bigger when they’re putting well. Baseball players say the ball seems bigger when they’re hitting well. But what about the perceived speed of the baseball?
Today at the VSS (Vision Sciences Society) conference I saw a great poster where the researchers measured real-world perception of the speed of a tennis ball. Mila Sugovic and Jessica Witt asked players enrolled in beginning, intermediate, and expert tennis lessons to return balls launched by a serving machine at 50 to 80 miles per hour. After each shot, the players walked to a computer showing an animated ball moving toward them. They pressed a button to launch the ball, and again after they estimated the ball had been in the air for the same amount of time as the ball they had just hit.
Did the advanced players see the ball as moving slower than the beginners? Actually, the ability of the players didn’t predict their estimates. But when the players made a better shot, they saw the ball as taking more time to get to them.
Sugovic and Witt videotaped each shot and measured the actual time the ball took to travel to the players. They compared this to the players’ estimates. In general, players overestimated the speed of the balls, saying they took about 70 percent as long in the air as they actually did. But when players subsequently hit the balls out of bounds, their estimates of ball speed were significantly faster than when they hit a good shot. The difference in perception corresponded to about a 5 mile-per-hour difference in speed.
After the study was over, the researchers also asked players to estimate the height of the net. Players who had hit more shots into the net were significantly more likely to make higher net-height estimates!
Sugovic, M., & Witt, J. (2011). Performance affects perception of ball speed in tennis. Poster presented at Vision Sciences Society meeting, Naples, FL.
Best Illusion of the Year 2010
Posted by Dave on May 10, 2010 | 2 Comments
I’m here at the Illusion of the year contest, which is held at the symphony hall here in Naples, Florida. It’s an enormous room, just now beginning to fill with some of the pre-eminent vision scientists in the world.
Since I have journalist credentials for this conference, I was able to get a sneak peak at the illusions that will be presented. Unfortunately, there’s no wifi here, so I won’t be able to live-blog the proceedings, but I’ll try to get this post up as soon as possible after the event.
The contest winner was Koukichi Sugihara, who has created a remarkable three-dimensional physical illusion: Impossible motion: magnet-like slopes.
Four ramps appear to ascend up to a central junction. Then a hand appears and rolls marbles “up” each ramp, with each marble stopping at the top of the hill. They seem to inhabit a bizarre world with reverse gravity. Perhaps it’s done with magnets—except the balls are made of wood! Then the camera pans around the device and it becomes clear how it was done—the ramps are actually all downhill!
There’s a long movie with more illusions here.
Another great illusion, which didn’t end up winning a prize: Peter Tse’s illusion is Attention-based after-image rivalry. It’s based on a couple different perceptual phenomena, but combined in a unique way. To see the illusion, you stare at the image on the left, two superimposed rectangles, each with colored strips along the longest dimension. After staring for 60 seconds, you then look at the image on the right. The after-image appears over the two outlines, and you can easily shift your perception to see two different after-images, one corresponding to each rectangle.
I’ll have another post about the contest tomorrow.
Live Blogging at VSS
Posted by Dave on May 8, 2010 | Comments Off
I’m here at the Vision Sciences Society 2010 convention in Naples, Florida — a fantastic meeting of vision scientists from around the world. So far the wifi is working well, so I’m going to try liveblogging a session. The session I’m at is “Motion: Perception,” moderated by Scott Stevenson.
First speaker: Albert van den Berg: The vestibular frame for visual perception of head rotation
When you move through a scene, there are two aspects of movement: translation, and rotation.
Did an fMRI study. simulating the rotation of the head while participants were still in the fMRI machine.
Participants had to wear a special contact lens to see the screen because it was extremely close to the head.
“rotated” at varying speeds, around three different axes. The display looks sort of like what you see in sci-fi movies, when a ship is about to enter into warp speed and the stars are moving by.
They were able to identify the brain activity associated with each type of rotation. For each individual, this occurred in a slightly different region of the brain.
Spinning ellipses perplex the visual system
Posted by Dave on May 7, 2010 | 4 Comments
Take a look at this video (Click on the image to play, QuickTime required):
Which ellipse is rotating faster?
While at first it seems quite obvious that the ellipse on the right is rotating faster, if you download the movie and play in loop mode, by counting rotations you should be able to convince yourself that they are actually rotating at the same speed.
The next question, of course, is why. Gideon Caplovitz, Po-Jang Hsieh, and Peter Tse systematically studied the question in a paper they published in 2005. They showed viewers dozens of movies like the one above, with one ellipse always the same fatness always rotating at the same speed (126 degrees per second). In each movie, the width and speed of the second ellipse was systematically varied, and viewers judged which ellipse seemed to be rotating faster. This graph shows the results:
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The Daily Monthly is Dave Munger's multi-layered exploration of ideas and issues affecting all of us today.
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