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The Neuroscience of Illusions and Dictionaries
Scientific American is running a pair of stories about what words and illusions can tell us about the brain. Mark Changizi of the Rensselaer Polytechnic Institute is interviewed about his research into the relationship between the mechanisms of the brain and the evolution of language. The second article contains a slide-show of various illusions and why the brain interprets them as it does.
American Scientist ran an article about Light traps for light processing, Tip-of-the-Tongue processing states of memory and speech creation, Parkinson's Disease discussion, and a Moon surface discussion.
And Scientific American (spit) runs yet another optical illusion article. I knew there was a reason why we dumped them and went AmSci.
Link to the one-page/print version of the dictionary article and the meat of the illusion article
Also, a summary of the illusion article: The brain uses context, rather than absolute sampling.
Even I have been trying to figure out why my boss's brain works the way it does, since ages. And it never made a news.
Why do LED clocks jiggle up and down when I'm eating crunchy things?
it's a blue bright blue Saturday hey hey
an article on the Bush Administration
I had always wondered why elephants had forward-facing eyes, since they are not predators... and this helps explain it. I had always supposed that it was because they were social animals, and communication ability and multiple individuals scanning for threats was better than one individual with a larger field of view. This makes even more sense if the scanning in a smaller area is more effective due to the binocular vision associated with forward-facing eyes.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
In the first FA, Changizi states his hypothesis that primates evolved color vision in order to detect changes in emotional state indicated by things like blushing/flushing of the face. I find this a bit problematic, primarily because it doesn't explain why our vision evolved to respond to three different wavelength ranges of light (red, green, and blue). It would make more sense to have only evolved cones responsive to red light, or perhaps red and one other color, if that were the only reason.
It seems to me that a more reasonable hypothesis is that trichromatic color vision co-evolved along with the colorings of fruits that primates would find nutritious. Emotional cues seem like a more subtle issue - as well as a mostly-solved problem - that would have taken advantage of color vision that was already partially or fully evolved.
Maybe I missed something, but I found the second article to be a let-down.
(Warning for epileptics: if visual stimuli can set off a seizure for you, you should probably stay away from the following links. I am not susceptible, but I found the second link to be visually overwhelming at first.)
IMHO, more interesting galleries of examples can be found at Wikipedia's Optical Illusions page and at Michael Bach's 78 Optical Illusions & Visual Phenomena page.
Can someone please explain the "illusion" behind the grey tiles?
:P
http://www.sciam.com/media/gallery/2B21EB44-BA10-8BF8-02EDC7FC3DF3CDEF_1.jpg
It challenged the reader to print out the image, cut out the two squares and compare them, which I did. Fair enough, sqaure A is a bit darker than the other light grey squares (didn't notice that prior to printing it out) but it is still much lighter than square B.
Are my eyes messed up? Or my brain?
Is anyone else having trouble reading the second article? The image on the left keeps distracting me, with its pretend turning of ultimate attention attainment.
I've seen my share of optical illusions, but the first one in the slideshow really got me. Its the one with the checkerboard and shadow, where squares A and B are actually the same shade, but B appears lighter because of the context (surrounding squares are darker).
I honestly thought it was BS until I cropped two copies of the image and compared the two squares side by side...
LiquidGeneration has another slideshow of optical illusions (SWF).
Another great resource for this stuff is the "Best Visual Illusion Contest of the Year" page that's sponsored by (and done at) the Vision Science meeting every year:
http://illusioncontest.neuralcorrelate.com/
These are the newest and most interesting illusions that are found every year. Some of them are very interesting and quite clever.
Here is a bunch of old optical illusions that you've seeen a billion times before. We still aren't to sure what causes them.
I may agree with what you say, but I will defend to the death your right to face the consequences of saying it.
Quoting from the slide show link:
The whole philosophy of perception that this quote embodies is fundamentally wrong. As an example of this, take a look at the first so-called "illusion" in the slideshow: the Edward Adelson checkerboard-and-shadon example. This is called an "illusion" on the basis that our eyesight "misleads us" by telling us that a light square in the shadow is lighter than a dark one in the light, whereas they are, supposedly, "the same color." By "the same color," what they seem to mean is that the stimulus, i.e., the rays of light reflected or emitted from the squares that hit our retina, have the same spectrum and intensity.
What they're missing is that the point of vision, and perception in general, isn't to give us information about the rays of light that hit the retina. What vision does is give us information about the objects in our environment, which reflect or emit rays of light. The reason we see the two squares as having different colors, despite the fact that our retinas are getting the exact same pointwise stimulus from them, is because the visual system, using contextual information about light and shadow across the whole scene, can figure out that the surface spectral reflectivity of the two squares must be different. Square B looks lighter than square A because the visual system judges, correctly, that it must reflect more light. Or put alternatively: the visual system figures out that if the two squares were in the same light, the point stimulus from the reflected light rays would be different.
This is accurately reproducing an aspect of the physical reality of the outside world; vision is accurately reproducing the spectral reflectivity of surfaces in our environment, at the apparent expense of failing to reproduce the spectral distribution of the rays of light that hit our retina. But of course, the answer to that one is that the rays of light aren't the object of visual perception, they're just the means.
Seeing the squares as different colors is not an illusion. There is only one visual illusion in that example, and they don't remark on it: the illusion of seeing, in a flat surface, a 3D scene with light and shadow. The judgement that the two squares have different colors follows from that, because in the real-world scene the image depicts, those squares would in fact be surfaces with different colors when seen under the same light.
Are you adequate?
...strong AI cannot come from the processing of real data. That is not how minds work. Minds exist in a self-contained virtual reality that are periodically updated with real-world sensory data. This is why autism can impact the flow of that data and its connectedness without impacting the underlying mind. They're simply not associated in that way.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
FTA: across different languages most characters take three strokes to write out. That's because, he says, three is the highest quantity a person's brain can perceive without resorting to counting.
The pips on my six-sided die say otherwise.
of the color vision paper and the alphabet paper:
[url=http://journals.royalsociety.org/content/?Author=Mark%20A.%20Changizi]
Usage: km/h for speed (kilometers per hour); kph for very slow impulses (kilopond hours).
Let us grant your second suggestion: that dichromatic vision is sufficient for detecting changes in emotional state. What that would mean is that the task requires no less than two kinds of photoreceptor, and that both dichromats and trichromats will become more common in the population than monochromats. However, you've given us no reason to think that the dichromats would be better off than the trichromats. We could end up with a majority trichromat population not because trichromats would be fitter than dichromats, but just because the original population had a mutant allele for trichromatism but none for dichromatism.
Of course, all my argument shows is that both Changizi and you would need to pursue other lines of argument to settle the dispute.
... of the fifteen optical illusions only about a third of them did I see the optical illusion without first reading the caption.
After reading the caption and looking fo rthe illusion I was able to see more.
I had never heard about the number 3 being the highest a person can perceive without counting, but I do know that odd numbers are more pleasing to the eye. (People generally like looking at triangles or photos of three cherries as opposed to rectangles and photos of two cherries.) So the question becomes, is it that the action of making three strokes in a letter is more pleasing, or is it looking at the result that we like? Probably, it is both.
Chok-sa!
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
What they're missing is that the point of vision, and perception in general, isn't to give us information about the rays of light that hit the retina. What vision does is give us information about the objects in our environment, which reflect or emit rays of light. The reason we see the two squares as having different colors, despite the fact that our retinas are getting the exact same pointwise stimulus from them, is because the visual system, using contextual information about light and shadow across the whole scene, can figure out that the surface spectral reflectivity of the two squares must be different. Square B looks lighter than square A because the visual system judges, correctly, that it must reflect more light. Or put alternatively: the visual system figures out that if the two squares were in the same light, the point stimulus from the reflected light rays would be different.
Uh-huh, but that's not what the scene depicts, nor is it the basis of the illusion.
There's two types of color we're talking about here. There's the surface property of the objects if viewed in equal light, like the color of paint that was used to paint the squares or its reflectivity. Then there's the appearance of the object based on its current actual lighting conditions. I'll call these "absolute" and "shadowed" for want of better terms, hoping you'll understand.
There is absolutely no problem with our eyes perceiving both somethings absolute color and its shaded color. If you saw two objects of the same absolute shade, but one was in shadow, you would easily be able to see both that the objects were the same absolute color, while also perceiving the one in shadow to be darker.
Just because our eyes/brain make deductions about the properties of a surface based on the lighting, does not mean it actually throws the lighting information away afterwards. We see shadows as darker. We can compare both the absolute color of two things and the shadowed appearance of the two things.
The point of this illusion is not just that B appears "lighter", as in the deduction that B is a light-painted square and A is a dark-painted square. That's obvious, and not the illusion. The illusion is that the shaded appearance of B is such that it is still much brighter than A.
And it is an illusion. In fact, it's just a twist on the usual contrast illusion where a medium gray shade appears very light on a black background, and dark on a white background. The fact that the transition from light to shadow is broken up by the darker squares is what causes the illusion.
One way to show this is to modify the image. Remove the dark squares around B, replacing them with light squares. Keep the shadow intact. It then becomes obvious that:
1) B is still an "absolute" lighter color than A, i.e. if they were in the same light, B would be lighter than A. The very thing you say your brain is deducing and causing you to perceive B as a lighter "shaded" color as well.
2) B's relative "shaded" color is about the same as A. I.e. the shadow darkens B to the point where it appears about equal to A. The very thing you say your brain doesn't perceive in order to tell you the more important (1).
So, you proposed that in the original image you did not perceive (2) because your brain was really after telling you (1). That is in part true, but the reality is that your brain can tell you both things... Were it not for the optical illusion which misleads you.
The enemies of Democracy are