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It's Surprisingly Hard To Notice When Moving Objects Change
An anonymous reader writes "Scientists at Harvard have found that people are remarkably bad at noticing when moving objects change in brightness, color, size, or shape. In a paper published yesterday (PDF) in Current Biology, the researchers present a new visual illusion that 'causes objects that had once been obviously dynamic to suddenly appear static.' The finding has implications for everything from video game design to the training of pilots."
Is that why my wife is always running around ?
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I think this was fairly well known (at least intuitively) by magicians. As long as you keep your hands moving, people can't tell what you are doing with them.
Our eyes are trained to do a whole lot of quick thinking and estimates before sending the raw data to our brain. This is one of the many reasons why simply hooking a camera up to the optic nerve doesn't quite produce the desired results - though our brains seem to be super-learning computers able to interact with almost any other kind of Input - Output, given enough time for trial and error.
I imagine our Eyes are trained to generalize the colour it sees and focus on the appearance of motion, because thats usually more important and relevant to survival, and our eyes are just like technology: Limited bandwidth.
You might call it a defect, I might think of it as evolutionary design.
IAAVN (I am a Visual Neuroscientist). It's a compelling illusion. I have not read the original paper, but will speculate nevertheless in true Slashdot fashion. The change that's perceived before the ring rotates is not so much due to the colors changing -- if you pay close attention -- but something that's called apparent motion. The classic example of apparent motion is the sequencing of lights around a movie marquis -- they appear to move, although the lights themselves are not actually moving. In the same way, the static ring has internal apparent motion as the colors change, because your brain is interpreting, for example, one dot turning yellow next to a dot that was previously yellow, as motion of a yellow dot, even though the underlying dots do not move. While apparent motion can be very strong, it is not the same as true motion.
Then, when the ring starts to rock back and forth, there is a true motion signal that swamps the apparent motion. If you pay attention to a given dot while holding your gaze still fixed at the central white point (not as hard as it sounds), you can clearly still see the colors changing.
So without having read the paper, I reserve some skepticism that they have not actually measured what they think they have. Change is still perceptible, but it would seem that real motion interferes with apparent motion.
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Switching something when it is in the middle of fast movement is the basis of all kinds of slight of hand tricks. There's just a certain state where the mind identifies something just as a blurb of overlapping color, rather than anything processed meaningfully, and you can freely swap it with a similar item without any notice. Mix in basic misdirection, and you can fool almost anyone's expectations. It's also why you kind of have to learn to juggle by feel & pattern rather than just sight - because the hand really does have to be faster than the (mind's ability to process information from the) eye to keep up with the pattern.
Ryan Fenton
As a magician, I have known this for years. Dai Vernon, The Professor, explains that concept the scientists just discovered as a simplistic beautiful statement, "A larger action covers (or hides) a smaller action." Science finally catches up to the magicians.. Damn them. :-)
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Unfortunately the video player had no indication that it was not loading at all (likely slashdoted), instead just sits static on the first frame. However, it took me about 30 seconds of staring at the static image wondering if my since of perception was so bad I -didn't see anything moving at all-
Turns out it is pretty bad, just not in the way I thought; I recommend going straight to the youtube versions linked on the article.
It's a pretty neat effect, sort of one of those things that become pretty obvious once you see it.
Follow the link to the youtube video - they have the bandwidth!
"Scientists at Harvard have found that people are remarkably bad at noticing when moving objects change in brightness, color, size, or shape..."
That may be because our eyes are exposed to so many different lighting conditions that our auto-white-balance is kicking in.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
Who only noticed a *diminished* sense of the colors changing? I could still see the colors changing, it just didn't seem to be nearly as much as before the dots started moving. My experience was as follows: 1) Ok, colors changing 2) dots moving and wow the changes stopped! 3) oh wait, no I'm seeing a few changes still....
Because in a primitive, hostile environment, the main thing is to see the enemy / victim coming. That's one of the reasons why people keep watching anything that moves above static parts. That it also changes color.. well.. big deal. Noticing it moving is much more important.
Decepticons have known this trick for aeons....
The reef squid has the ability to quickly change colors and patterns on it's body, and seems to signal other squids in this fashion (as well as for camouflage). I wonder if they would be fooled by this illusion or if their neural optics are wired very differently than ours. It would be challenging to try to create an objective test that you could do with them.
I won't necessarily claim to be one here, since anyone can claim anything on the internet. But I wonder how well experienced MTI analysts (http://en.wikipedia.org/wiki/Moving_target_indication) would perform against these videos. Quite literally, it is the job of an MTI analyst to distinguish coherent from non-coherent changes across a vast number of moving dots displaying all sorts of crazy behaviors.
Additionally, I would prefer to see this experiment run under different conditions, such as having the videos begin with dots in apparent motion for many seconds, then having them stop moving. I do think the results of the experiment are damaged by having the motion segment (3 secs) be significantly shorter than the non-motion segment (5 secs) and always happening after the eyes and brain have adjusted to the lack of apparent motion.
I think another big problem with the videos provided is that the motion segment alters direction 9 times (counting first and last) within a short window -- this may not result in the human mind having difficulty seeing change in moving objects, but a difficulty in adjusting the perspective of the total scene to something observing rapid fluxuation in velocity. (I.E. The circle constantly rotates back and forth, preventing the brain from "getting used to" the scene, whereas when the dots are stationary and only changing in specific property, they remain in this configuration for a much longer period of time).
It's a interesting topic, but research could have focused more on overall configuration of how viewers were presented with the experiment. There isn't enough information present to draw an accurate conclusion from these observed results.
It seems to me that this is a fairly simple illusion: the frequent event is "more interesting" hence the brain focuses on that. Color change in this example is happening slower than rotation hence motion is favored instead of colors.
Maybe if our ancestors had fed on flocks of fast moving chameleons we would be better at this.
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"I can even see color with it" ...is this supposed to be odd or something?
Yes, because only the cones in the center of your eye are capable of perceiving color (the rods on the outside perceive only black and white.) Your brain senses everything in the periphery of your vision in black and white, but "fills in" best-guess colors from what your cones perceive directly in front of you.
I remember that from a psychology lecture only because a fellow classmate, like the parent poster, couldn't believe the color in his peripheral vision was an illusion. So, the professor drew an "X" in the middle of the chalkboard and asked him to stare at it without looking away. He then held up a colored note card directly in front of the "X" and asked him to name the color. (Of course, he named it correctly.)
The professor held up another note card, a bit further away from the X, and asked him to say what color that card was. And then he held up the next card, a bit further away from the X than the last one. And he kept holding the cards further and further towards the edge of his field of vision.
After about the fifth card, the kid was convinced that any card the professor held up was either a shade of gray, or the same color as the chalkboard. Once the note cards were in his peripheral vision, he couldn't tell what color they were, and couldn't tell that he couldn't tell what color they were. Great professor.
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instead of making a video, couldn't they have made a flash thingie, so that you could change the parameters of the illusion too? maybe we could then tell at what rotation speed color change becomes hard to notice.
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Except that's not what they tried to show. The site demonstrates that when objects are moving relative to your field of view you become less able to discern changes to the objects themselves, whether it's a change in coloration, size or shape. This is not interesting because your peripheral vision is bad - when the objects are stationary it's easy to tell that they are changing - it's interesting because it's a property of human vision that apparently wasn't known yet.
In fact, just try to focus on one of the dots in the videos. Even if you know it's going to move, you know it's going to keep changing color and the dot is in your center of view you still might fall to the illusion (not to mention that other dots nearby also seem to be unchanging even though they're right next to the one you're trying to follow).
It's not about central vs. peripheral sight, it's about how motion and the perception of change interact.
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"people are remarkably bad at noticing when moving objects change in brightness, color, size, or shape"
I think you left out an important qualifier:
people are remarkably bad at noticing when moving objects change in brightness, color, size, or shape IN THEIR PERIPHERAL VISION
If you look directly at any of the moving objects you can see any of them change in brightness, color, size, or shape. Your peripheral vision is not your focus for good reason, and of course its not going to track every single change like at the center of your focus of vision, its not supposed to and is better that it doesn't.
I'd like to see if there's a culture bias to this. Get someone from a very non-westernized culture and ask what they see. They're regularly not fooled by these kinds of "illusions":
Which line is longer:
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Their eyes just aren't trained to see geometry the same way as westerners who are faced with tons of man-made things everyday.
"That which does not kill us makes us stranger." -Trevor Goodchild
Uh, did you read the Wikipedia link you posted? "Cone cells are densely packed in the fovea, but gradually become sparser towards the periphery of the retina." They aren't located only in the fovea, but all across the retina. They're merely more densely packed in the fovea than towards the edge. What most likely happened to your classmate is cone bleaching: the longer you stare at a particular image, the more the particular cones bleach their photoreceptors, and the harder it is to figure out the correct color. Depending on what color the chalkboard was, it's quite possible he simply had stared at it for too long.
The retina still perceives color at the edges, it just does so less effectively than if you focus on the center.
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