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Science

The Neuroscience of Illusions and Dictionaries 72

Posted by Soulskill from the maybe-your-brain-is-just-a-jerk dept.
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.
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The Neuroscience of Illusions and Dictionaries More

The Neuroscience of Illusions and Dictionaries

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  • Link to the meat (Score:5, Informative)

    by SheeEttin ( 899897 ) <sheeettin&gmail,com> on Sunday June 01, 2008 @11:18AM (#23617855) Homepage
    Link to the one-page/print version [sciam.com] of the dictionary article and the meat of the illusion article [sciam.com]
    Also, a summary of the illusion article: The brain uses context, rather than absolute sampling.

  • So can somebody explain? (Score:4, Interesting)

    by quokkapox ( 847798 ) <quokkapox@gmail.com> on Sunday June 01, 2008 @11:29AM (#23617931)
    Why do LED clocks jiggle up and down when I'm eating crunchy things?

    • Re: (Score:1, Funny)

      by Anonymous Coward
      Because you touch yourself at night.

    • Re: (Score:2, Informative)

      by Vectronic ( 1221470 )
      The change in (fluid) pressure in your eyes (because of muscles contracting/expanding), aswell as slight variation of the position between both your eyes (since we arent perfectly semetrical) from vibration, etc.

      • Re: (Score:1, Interesting)

        by Anonymous Coward
        You got 1/2 credit. I think the intent of the question is, why don't other light sources, beside LEDs, jump up and down when I chew?

    • Re:So can somebody explain? (Score:5, Informative)

      by Dachannien ( 617929 ) on Sunday June 01, 2008 @11:45AM (#23618051)
      The LEDs aren't actually illuminated all the time. They are actually flashing very fast - faster than your brain can discern. When you eat crunchy foods, it vibrates your head (and therefore, your retinas) at a frequency sufficient to allow some of the LED flashes to appear above or below the other flashes.

      • Re:So can somebody explain? (Score:4, Insightful)

        by Trogre ( 513942 ) on Sunday June 01, 2008 @11:21PM (#23623089) Homepage
        I can discern Pulse-Width Modulated LEDs without eating :) By rapidly oscillating my eyes I can tell you in a second which light sources in a room are PWM. Car brake lights, dashboard lights, billboard signs, power LEDs - it's surprising how much equipment is now PWMd. That unfortunately includes other POV-based technologies like DLP. I see the rainbow effect in every single-chip implementation that I've ever come across.

    • Re: (Score:2, Informative)

      by LordCobalt ( 1299905 )
      ...And another reason might be if you wear glasses, the chewing action will alter where your glasses actually focus on.

    • Re:So can somebody explain? (Score:4, Funny)

      by Eighty7 ( 1130057 ) on Sunday June 01, 2008 @12:22PM (#23618383)
      Hang on, do you weigh less than a duck.

    • Re: (Score:2)

      by PPH ( 736903 )
      That depends on what it was that gave you the munchies.

    • Re: (Score:2, Insightful)

      by Moodie-1 ( 966737 )
      Dachannien's explanation is the correct one. LEDs sometimes use 'multiplexing' power sources, causing the segments to flicker when you move your eyes quickly. This is also true of some of the newer LED automobile tailights.
      • This is also true of some of the newer LED automobile tailights.

        For me, these new LED tailights are really distracting, as I see them flickering as they go past. I also find push-bike LED tailights that flash patterns annoying as hell.

        I don't have any flicker problems with LED torches or traffic signals, just the rear LED's on cars and trucks.

    • Re: (Score:1)

      by Tomfrh ( 719891 )
      When you eat something crunchy your head vibrates.

      LEDs turn on and off very quickly.

      The jiggle you observe is the inteference pattern between these two phenomena.

  • Binocular vision and elephants (Score:5, Interesting)

    by Red Flayer ( 890720 ) on Sunday June 01, 2008 @11:43AM (#23618043) Journal

    For the evolution of forward-facing eyes, I am arguing that it is for a kind of x-ray vision. It actually allows us to see through stuff--like when you hold up a finger vertically and you see through it instead of beyond it. For animals that are large and living in forested environments, there should be selection pressure for forward-facing eyes, because you can actually see more of your environment.
    That makes a lot of sense, and is very interesting to me since I recall learning that predators have forward facing eyes so they can better detect movement of prey (binocular vision) while prey animals have outward facing eyes so they can better be aware of threats (greater field of vision).

    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.

    • Re: (Score:3, Insightful)

      by Hektor_Troy ( 262592 )
      Actually a short film on National Geographic made a good point.

      If we didn't have forward facing eyes, just how effective would our hands be? We'd have lots of trouble grabbing things, because we'd have a very hard time judging the proper distance. Same with manipulating things.

      Granted, elephants aren't exactly known for having hands, but they do use their trunk for a LOT of gripping and manipulating. How much trouble would they have, if they didn't have forward facing eyes?

  • Rods and cones (Score:5, Insightful)

    by Dachannien ( 617929 ) on Sunday June 01, 2008 @11:55AM (#23618159)
    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.

    • Re: (Score:2)

      by gmuslera ( 3436 )
      As i see it, what we have is what we got and gave us at least for enough time a survival or mating advantage to make it in our common gene pool. Being able to detect emotions fits in that scheme, specially if things like emotions get more complicated than with lower animals, so have some rationality.

      But detecting fruit colors never was a survival requirement for animals that have it as its main food.

      Still, i agree that it shouldnt be the only factor there. If seeing changes in body heat was just what was ne

    • Subtle flaw in your argument (Score:1, Interesting)

      by Anonymous Coward

      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.

      Let us grant

    • Re: (Score:3, Interesting)

      by SoupIsGoodFood_42 ( 521389 )
      But in order to see red best, you need to be able to detect what is not red. If you want to see why, take a photo of a colourful scene then create two versions in Photoshop, make one greyscale, then on the other one, use the channels pallet to look at each channel separately. A bright red object in the red channel will look the same as a white object, while the other channels will show it as very dark. Obviously, human vision doesn't work exactly like this, but the same principle still applies: The best way

  • More/Better Optical Illusions (Score:5, Interesting)

    by martyb ( 196687 ) on Sunday June 01, 2008 @12:05PM (#23618237)

    The second article contains a slide-show of various illusions [CC] [GC] and why the brain interprets them as it does.

    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 [wikipedia.org] page and at Michael Bach's 78 Optical Illusions & Visual Phenomena [michaelbach.de] page.

    • I rather agree. All it really says for "why the brain interprets them as it does" is, as another poster mentioned, "context". I think that link would be better suited to idle.slashdot.org.

    • Another Great Resource (Score:3, Interesting)

      by Ieshan ( 409693 )
      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/ [neuralcorrelate.com]

      These are the newest and most interesting illusions that are found every year. Some of them are very interesting and quite clever.

  • Difficulty RTFA (Score:2, Informative)

    by pgn674 ( 995941 )
    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.

  • Serious conceptual flaws (Score:5, Insightful)

    by Estanislao Martínez ( 203477 ) on Sunday June 01, 2008 @02:38PM (#23619455) Homepage

    Quoting from the slide show link:

    It's a fact of neuroscience that everything we experience is actually a figment of our imagination. Although our sensations feel accurate and truthful, they do not necessarily reproduce the physical reality of the outside world. Although our sensations feel accurate and truthful, they do not necessarily reproduce the physical reality of the outside world.

    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 [sciam.com]. 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.

    • I don't think they're missing that; I bet they'd agree with what you're saying. You just seem to disagree with their terminology (e.g. "illusion").

      Also, what is the difference between seeing 3D in a 2D surface and seeing 3D in a 3D "surface"? Like the Flatlander that sees a penny as a line (he can only see one-dimensional information), everything we see is actually a 2D image translated into a 3D construction in our brain.

      • Re: (Score:2, Insightful)

        by Estanislao Martínez ( 203477 )

        I don't think they're missing that; I bet they'd agree with what you're saying. You just seem to disagree with their terminology (e.g. "illusion").

        No, it's not just a disagreement about terminology. It's a disagreement about what the object of vision is. I take it we all agree that what vision does is to give us information about the environment. The disagreement is about assumptions about what that information is. Is it information about the rays of light that hit the retina, or about the surfaces tha

        • Perhaps one or both of us are not communicating well. I don't see what your argument has to do with mine. By 3D "surface", I did not mean the surface of a table or a car, but the entire table or car itself, as a 3D "projection" on, for example, a 4D hyperplane. Anyway, you raise interesting points. And if we had time to sit down and converse, we'd probably clear everything up and come to one agreement or another.

          • By 3D "surface", I did not mean the surface of a table or a car, but the entire table or car itself, as a 3D "projection" on, for example, a 4D hyperplane.

            Let me try it this way: perception is about acquiring information about the environment of an organism. The environment isn't just a 3D surface (in the mathematical sense you're using) that the organism sees; it's a world that the organism inhabits. The organism moves around the environment and interacts with its features and objects with its limbs, et

    • Re: (Score:2, Interesting)

      by Anonymous Coward
      "It's a fact of neuroscience that everything we experience is actually a figment of our imagination. Although our sensations feel accurate and truthful, they do not necessarily reproduce the physical reality of the outside world. Although our sensations feel accurate and truthful, they do not necessarily reproduce the physical reality of the outside world."

      I think you totally misunderstood what they were getting at, poorly chosen words. According to physics of relativity, "insideness vs outsideness" is an

      • Re: (Score:3, Insightful)

        by Estanislao Martínez ( 203477 )

        According to physics of relativity, "insideness vs outsideness" is an illusion of consciousness.

        I don't think physicists have very much to tell us about psychology or philosophy. What they think is not completely irrelevant, but it is not imbued with the authority you pretend it should.

        Reality is a continuous field. i.e. If we were in a simulation you wouldn't know it. There is no object "out there" per se, all your mind is doing is discretizing a continuous surface of data that you percieve or have acces

    • 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.

      But that makes assumptions about the evolution of vision.

    • Re: (Score:2)

      by Trogre ( 513942 )
      Uhm. Yes it is an illusion.

      The challenge is to compare the *ink* colours (lightness, hue, whatever) in two sections of that picture. The other prompts in the picture are there solely to inhibit the capability to accurately make a comparison by producing an illusion of a shadow cast by a cylinder.

      The fact that one cannot easily do this as with a flat checkerboard for example, is what makes it an illusion.

    • I think you are overstating your case and playing with semantics a bit. How do you know so definitively the point of vision which I think is itself a shaky concept evolutionarily speaking since it is emergent. I think your statements make a lot of sense, but I don't see how they are contradictory with the article or how they missed any big point.

      In fact, it seems to me that your "purpose" of vision fits quite well with their basic idea of "perception is only a representation of reality."

      • How do you know so definitively the point of vision which I think is itself a shaky concept evolutionarily speaking since it is emergent.

        That's a fair point. I was definitely sloppy about that, in the interest of advancing other parts of the argument.

        When I say "the point of vision," I don't mean that nature is teleological. "The point of vision" is the set of functional assumptions that the researchers make, and guide their investigation. My argument is that by accepting the idea that people's "failur

        • Interesting. I had never read that as a formal philosophy. In general, I tend to agree with the basic tenet. I seems to me that it is an inescapable truth that our "thoughts/brain" are separated from the world by our senses. Some exceptions would be getting your brains shaken up in a concussion, an aneurysm, brain surgery, etc. But those are not really perceivable by us except as disruptions to our normal brain function.

          Independent of this illusion discussion, if you don't mind, could you tell me if there i
    • 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

      • 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

  • This is why... (Score:5, Insightful)

    by jd ( 1658 ) <imipakNO@SPAMyahoo.com> on Sunday June 01, 2008 @03:41PM (#23619883) Homepage Journal
    ...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.

  • > 3 (Score:1, Funny)

    by Anonymous Coward
    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.

    • 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.

      If we wrote Morse code, yes. To my knowledge (which may be false) most writing systems distinguish symbols primarily by their shapes, not by the number of strokes. Then again, TFA may be misleading. From Changizi's own page [geocities.com] (gasp! a source reference!) "(1) The number of strokes per character is approximately three, independent of the number of characters in the writing system; numeral systems are the exception, having on average only two strokes per character. (2) Characters are approximately 50% redunda

  • ... 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.

    • Re: (Score:3, Interesting)

      by icegreentea ( 974342 )
      I've heard about this before, and I think it's vaguely true. I can easily pick out 3, 4, or even 5 objects without having to count, of having them in any particular formation/sequence. But if you gave me 6 objects in a random configuration (without showing me a lesser number before hand), I really would have to count. Case in point is Roman Numerals (and Chinese I guess). Roman Numerals (now) goes up to III before IV (though apparently it use to go up to IIII). Chinese does the one stroke, two stroke, three

    • Re: (Score:1)

      by dfedfe ( 980539 )
      You may be interested in the term subitization [wikipedia.org]: the ability to rapidly determine numerosity for small sets of items.
  • ...is this guy [sciam.com] a Fremen, or what?


    Chok-sa!

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