Posts Tagged ‘stereo’

Today I was on LateNightLive (of ABC Radio National) with host Phillip Adam.  In addition to divulging my enjoyment at running over pigeons, I got a chance to talk about sex, blood, the blind, writing, rabbit-heads and other topics from The Vision Revolution.

Late Night Live

Late Night Live

Check out the segment here. (Download the mp3.)

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

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This first appeared on October 26, 2009, as a feature at ScientificBlogging.com

Later this evening I’ll be giving a talk to a group of astronomers on what its like to see like an alien. The beauty of this is that I can speculate until the cows come home without fear of any counterexamples being brought to my attention. And even if an alien were to be among the audience members and were to loudly object that he sees differently than I claim, I can always just say that the jury is out until we get more data, and then advise him not to let the door slam into his proboscis on the way out.

E.T. the extra-terrestrial

E.T.'s forward-facing eyes suggests its ancestors evolved in forests

Although it may seem wild-eyed to discuss the eyes of aliens, if we understand why our vision is as it is, then we may be able to intelligently guess whether aliens will have vision like ours.

And in addition to the fun of chatting about whether little green men would see green, there are human implications. In particular, it can help us address the question, How peculiar is our human vision? Are we likely to see eye to eye with the typical alien invader? Or does our view of the world differ so profoundly that any alien visual mind would remain forever inscrutable?

Let’s walk through four cases of vision that I discuss in my book The Vision Revolution and ask if aliens are like us.

Do aliens see in color like us?

Let’s begin with color. I have argued in my research that our primate variety of color vision evolved in order to sense the skin color signals on the faces, rumps, and other naked spots of us primates. Not only are the naked primates the ones with color vision, but our color vision is at the sweet spot in design space allowing it to act like an oximeter and thereby see changes in the spectrum of blood in the skin as it oxygenates and deoxygenates. (See the journal article.)

Aliens may be interested in eating our brains, but they have no interest whatsoever in sensing the subtle spectral modulations of our blood under our skin. Aliens will not see color as we do, and will have no idea what we’re referring to when we refer to “little green men.”

Little green men may not think they look green

This can take the wind out of many people, namely those who feel that their senses give them an objective view of the world around them. But evolution doesn’t care about objective views of the world per se. Evolution cares about useful views of the world, and although veridical perceptions do tend to be useful, little-white-lie perceptions can also be useful. We primates end up with colors painted all over the world we view, but our color vision (in particular the red-green dimension) is really only meaningful when on the bodies of others. Although we feel as if the objects in our world “really” have this or that color, no alien would carve the world at the color-joints we do.

Do aliens have forward-facing eyes?

How about our forward-facing eyes we’re so proud of? I have argued and presented evidence that forward-facing eyes evolved as an adaptation to see more of one’s surroundings when one is large and living in leafy habitats. Animals outside of leafy cluttered habitats are predicted to have sideways-facing eyes no matter their body size, but forest animals are predicted to have more forward-facing eyes as they get larger. That is, in fact, what I found. (See the article.)

So, would aliens have forward-facing eyes? It depends on how likely it is that they evolved in a forest-like habitat (with leaf-like occlusions) and were themselves large (with eye-separation as large or larger than the typical occlusion width). My first reaction would be to expect that such habitats would be rare. But, then again, if plant-like life can be expected anywhere, then perhaps there will always be some that grow upward, and want to catch the local starlight. If so, a tree-like structure would be as efficient a solution as it is for plants here on Earth. The short answer, then, is that it depends. But that means that forward-facing eyes are fundamentally less peculiar than our variety of color vision. Aliens could well have forward-facing eyes, but it would not appear to be a sure thing.

Do aliens suffer from illusions?

One of the more peculiar things our brain does to us is see illusions. I have provided evidence that these illusions are not some arcane mistake, but a solution to a problem any brain must contend with if it is in a body that moves forward. When light hits our eye, we would like our perception to occur immediately. But it can’t. Perception takes time to compute, namely about a tenth of a second. Although a tenth of a second may not sound like much, if you are walking at two meters per second, then you have moved 20 cm in that time, and anything perceived to be within 20 cm of passing you would have just passed you – or bumped into you – by the time you perceive it. To deal with this, our brains have evolved to generate a perception not of the world as it was when light hit the eye, but of how the world will be a tenth of a second later. That way, the constructed perception will be of the present. Although there is no room in this piece to describe the details, I have argued that a very large swathe of illusions occur because the visual system is carrying out such mechanisms. (See the paper.)

Are aliens buying books of illusions and “ooh”ing and “ah”ing at them like we are? If they are moving forward (and have non-instantaneous brains), then they probably are buying these books. This is because the optic flow characteristics that underlie the explanation of the illusions are highly robust, holding in any environment where one moves forward. Aliens are, then, likely to suffer from illusions. The illusions we humans suffer from, then, may not be due to some arcane quirk or mistake in our visual system software, but, instead, a consequence of running the efficient software for dealing with neural delays.

Is alien writing shaped like ours?

I have provided evidence that our human, Earthly writing systems “look like nature,” in particular so that words have object-like structure. And I have shown that for writing like ours where letters stand for speech sounds, letters look like sub-objects, namely object junctions. Certain contour-combinations happen commonly in natural scenes, and certain combinations happen rarely. I have shown that the common ones in such environments are the common letters shapes found in human writing systems. Culture has selected writing to have the visual shapes our illiterate brains can see, which is why we’re such capable readers. (See the paper, a popular piece, and an excerpt from The Vision Revolution on this.)

Would alien writing look like this?

In this light, would alien writing look like nature as well? It depends on how specific one is when one says “like nature.” If, say, our human writing looks specifically like a savanna – i.e., if our writing mimicked signature visual features of the savanna – then it would appear very unlikely that aliens would have our kind of writing. But what if human writing looks like a very general notion of nature, so general it is likely to apply to most conceivable aliens? In my research I have provided evidence that the “nature” that appears relevant for understanding the shape of human writing is, indeed, highly general: namely, “3D environments with opaque objects strewn about.” Although highly general, aliens could float in a soup of cloudy transparent blobs, which is a kind of “nature” radically different than the one that human writing looks like. But it does seem plausible that most aliens will be roaming around opaque objects in 3D, and if that’s the case, then (so long as their culture has selected their writing to harness their visual object recognition system) their writing may look similar to human writing. Alien writing, if thrown into a pile of samples across our human writing, might just fit right in!


So let’s take stock.

Would aliens have our color vision? No. Definitely not. Ours is due to our peculiar hemoglobin.

Would aliens have forward-facing eyes? Maybe. If they evolved in leafy habitats and were large.

Would aliens see our illusions? Probably.   If they move forward.

Would aliens have writing that looks like ours? Probably. If they live in a 3D world with opaque objects.

Mark Changizi is a professor of cognitive science at Rensselaer Polytechnic Institute, and the author of The Vision Revolution (Benbella Books).

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This is the Wall Street Journal review of The Vision Revolution that appeared earlier this year.

Why the Eyes Have It
We can read words, gauge distance and see color. How did that happen?

By Christopher F. Chabris

Why are we ­humans so good at seeing in color? Why do we have eyes on the front of our heads rather than on the sides, like horses? And how is it that we find it so easy to read when written language didn’t even exist until a few thousand years ago—a virtual millisecond in evolutionary time?


The Vision Revolution

By Mark Changizi

Ben Bella, 215 pages, $24.95

Read an excerpt of “The Vision Revolution”

Most of us, understandably, have never given much thought to questions like these. What is surprising is that most cognitive scientists ­haven’t either. People who study the brain generally ask how it works the way it does, not why. But Mark Changizi, a professor at Rensselaer ­Polytechnic Institute and the author of “The Vision ­Revolution,” is indeed a man who asks why, and lucky for us: His ideas about the brain and mind are fascinating, and his explanations for our habits of seeing are, for the most part, persuasive.

Mr. Changizi takes care not to call himself a practitioner of evolutionary psychology. This is the one discipline of the mind sciences that focuses on why questions, but it often answers them by telling just-so stories that cannot be ­disproved. (Why do men have better spatial ability than women? Because a long time ago, in Africa, men needed spatial skills to track prey and to kill at a distance—a plausible theory but one that is difficult to test with experiments.) Instead Mr. Changizi calls ­himself a “theoretical neuroscientist,” seeking explanations for the design of the mind that are based on mathematical and physical analysis. He has his own stories, it is true, but they are grounded solidly in neuroscience, and they are backed up by data about a surprising range of human activities, from ­the colors found in historical ­costumes to the ­correspondence between the shapes found in written letters and the shapes found in ­nature.

Let’s start with the question of color. It is such a natural part of our visual experience that we don’t stop to wonder why we can see it at all. ­Without color television there would have been no “Miami Vice,” of course, but were we really missing out on so much when we had only black and white? The consensus explanation for our superior ability to perceive color is that primates evolved it to see fruit—you can’t order dinner if you can’t read the menu.

Mr. Changizi thinks otherwise. He proposes that color vision is useful for distinguishing the changes in other ­people’s skin color—changes that are caused by shifts in the volume and oxygenation levels of the blood. Such shifts, like blushing, often signal emotional states. The ability to see them is adaptive because it helps an observer to “read” states of mind and states of health in others, information that is in turn useful for predicting their behavior.

Our brains evolved in a time when people lived their entire lives without ever seeing someone with a skin color different from their own. Thus the skin color we grow up seeing, Mr. Changizi says, is “neutral” to us: It serves as a kind of baseline from which we notice even minor deviations in tint or hue. Almost every language has distinct words for some 11 basic colors, but none of them aptly describe the look of skin, which seems colorless (except in our recent multicultural societies, where skin color is newly prominent). As one might expect, primates without color vision tend to have furry faces and hands and thus less need to perceive skin color; ­primates with color vision are more “naked” in this respect, humans most of all.

James Steinberg

Conventional wisdom may be similarly misleading when it comes to binocular vision. It is said that we have two forward-facing eyes, which send our brains two separate images of almost everything in our field of view so that the brain can compare those images to estimate the distance of objects—a generally useful thing to know. But people who are blind in one eye, Mr. Changizi notes, can perform tasks like driving a car by using other cues that help them to judge distance. He offers a different explanation: that two eyes give us a sort of X-ray vision, allowing us to see “through” nearby objects to what is beyond.

You can experience this ability yourself by closing one eye and holding your forefinger near your face: It will appear in your field of vision, of course, and it will block what lies beyond or behind it. If you open both eyes, though, you will suddenly perceive your finger as transparent—that is, you will see it and see, ­unblocked, the full scene in front of you. Mr. Changizi observes that an animal in a leafy environment, with such an ability, gains an advantage: It can lurk in tall grass and still see what is “outside” its hiding place. He correlates the distance between the eyes and the density of vegetation in the habitats of animals and finds that animals with closer-set eyes do tend to live in ­forests rather than on plains.

As for reading, Mr. Changizi stops to observe how remarkable this ability is and how useful, giving us access to the minds of dead people (i.e., deceased writers) and permitting us to take in words much faster than we can by merely listening to them. He claims that we learn to read so easily because the symbols in our written alphabets have evolved, over many generations, to resemble the building blocks of natural scenes—­exactly what previous millennia of evolution adapted the brain to perceive quickly. A “T,” for example, appears in nature when one object overlaps ­another, like a stone lying on top of a stick. With statistical analysis, Mr. Changizi finds that the contour patterns most common in nature are also most common in letter shapes.

Mr. Changizi has more to say about our visual experience—about optical illusions, for instance, which he sees as artifacts of a trick the brain uses to cope with the one-tenth of a second it takes to process the light that hits our eyes and to determine what is actually in front of us. He calls for a new academic discipline of “visual linguistics,” and he tells us why there are no ­species with just one eye.

What does all this add up to? Provocative hypotheses but not settled truth—at least not yet. As a theoretician, Mr. Changizi leaves it to others to design experiments that might render a decisive ­verdict. Someone else will have to study how accurately people can perceive mental states from shifting skin tones, and someone else will have to ­determine whether, in most cases, looking at another ­person’s skin adds any useful information to what is easily known from facial expression, tone of voice and body ­language.

Still, the novel ideas that Mr. Changizi outlines in “The Vision Revolution”—together with the evidence he does present—may have a big effect on our understanding of the human brain. Their implication is that the environments we evolved in shaped the design of our visual system according to a set of deep principles. Our challenge now is to see them clearly.

Mr. Chabris is a psychology professor at Union College in Schenectady, N.Y.
Mark Changizi is Professor of Cognitive Science at RPI, and the author of The Vision Revolution (Benbella, 2009) and The Brain from 25000 Feet (Kluwer, 2003).

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(BOOK EXCERPT, Wall Street Journal ; WSJ review here)

The Vision Revolution’ (Benbella Books, 2009)

By Mark Changizi



In the movie “Unbreakable” by M. Night Shyamalan, the villain Elijah Price says, “It’s hard for many people to believe that there are extraordinary things inside themselves, as well as others.” Indeed, the story’s superhero, David Dunn, is unaware of his super strength, his inability to be injured (except by drowning), and his ability to sense evil. Dunn would have lived his life without anyone—including himself—realizing he had superpowers if Unbreakable’s villain hadn’t forced him into the discovery.


At first glance we are surprised that Dunn could be so in the dark about his abilities. How could he utilize his evil-detection power every day at work as a security guard without realizing he had it? However, aren’t most powers—super or otherwise—like that? For example, our ability to simply stand requires complex computations about which we are unaware. Complex machines like David Dunn and ourselves only function because we have a tremendous number of “powers” working in concert, but we can only be conscious of a few of these powers at a time. Natural selection has seen to it that precious consciousness is devoted where it’s most needed—and least harmful—leaving everything else running unnoticed just under the surface.

The involuntary functions of our bodies rarely announce their specific purposes. Livers never told anyone they’re for detoxification, and they don’t come with user’s manuals. Neurosurgeons have yet to find any piece of brain with a label reading, “Crucial for future-seeing. Do not remove without medical or clerical consultation.” The functions of our body are carried out by unlabeled meat, and no gadget—no matter how fancy—can allow us to simply read off those functions in a lab.

Powers are even harder to pin down, however, because they typically work superbly only when we’re using them where and when we’re supposed to. Our abilities evolved over millions of years to help us survive and reproduce in nature, and so you can’t understand them without understanding the environment they evolved for, any more than you can understand a stapler without knowing what paper is.

Superpowers, then, can’t be introspected. They can’t be seen with a microscope. And they can’t be grasped simply by knowing the ins and outs of the meat. Instead, the natural environment is half the story. Lucky for us there are ways of finding our powers. Science lets us generate a hypothesis concerning the purpose of some biological structure—what its power is—and then test that hypothesis and its predictions. Those predictions might concern how the power would vary with habitat, what other characteristics an animal with that power would be expected to have, or even what that biological structure would look like were it really designed with that power in mind. That’s how we scientists identify structures’ powers.

And that’s what this scientist is doing in this book: identifying powers. Specifically, superpowers. Even more specifically, superpowers of vision—four of them, one from each of the main subdisciplines of vision: color, binocularity, motion, and object recognition. Or in superhero terms: telepathy, X-ray vision, future-seeing, and spirit-reading. Now, you might be thinking, “How could we possibly have such powers? Mustn’t this author be crazy to suggest such a thing?” Let me immediately allay your fears: there’s nothing spooky going on in this book. I’m claiming we have these four superpowers, yes, but also that they are carried out by our real bodies and brains, with no mysterious mechanisms, no magic, and no funny business. Trust me—I’m a square, stick-in-the-mud, pencil-necked scientist who gets annoyed when one of the cable science channels puts a show on about “hauntings,” “mystics,” or other nonsense.

But then why am I writing about superpowers? “No magic, no superpowers,” some might say. Well, perhaps. But I’m more inclined to say, “No magic, but still superpowers.” I call each of these four powers “superpowers” because each of them has been attributed to superhuman characters, and each of them has been presumed to be well beyond the limits of us regular folk.

That we have superpowers of vision—and yet no one has realized it—is one of the reasons I think you’ll enjoy this book. Superpowers are fun, after all. There’s no denying it. But superpowers are just a part of this book’s story. Each of the four superpowers is the tip of an iceberg, and lying below the surface is a fundamental question concerning our nature. This book is really about answering “why”: Why do we see in color? Why do our eyes face forward? Why do we see illusions? Why are letters shaped the way they are?

What on Earth is the connection between these four deep scientific questions and the four superpowers? I’d hate to give away all the answers now—that’s what the rest of the book is for—but here are some teasers. We use color vision to see skin, so we can sense the emotions and states of our friends and enemies (telepathy). Our eyes face forward so that we can see through objects, whether ourown noses or clutter in the world around us (X-ray vision). We see illusions because our brain is attempting to see the future in order to properly perceive the present (future-seeing). And, lastly,letters have culturally evolved over centuries into shapes that look like things in nature because nature is what we have evolved to be good at seeing. These letters then allow us to effortlessly read the thoughts of the living . . . and the dead (spirit-reading).

Although the stories behind these superpowers concern vision, they are more generally about the brain and its evolution. Half of your brain is specialized for performing the computations needed for visual perception, and so you can’t study the brain without spending about half your energies on vision; you won’t miss out on nearly as much by skipping over audition and olfaction. And not only is our brain “half visual,” but our visual system is by far the most well-understood part of our brains. For a century, vision researchers in an area called visual psychophysics have been charting the relationship between the stimuli in front of the eye and the resultant perception elicited “behind” them, in the brain. For decades neuroanatomists such as John Allman, Jon Kaas, and David Van Essen have been mapping the visual areas of the primate brain, and countless other researchers have been characterizing the functional specializations and mechanisms within these areas.

Furthermore, understanding the “why” of the brain requires understanding our brain’s evolution and the natural ecological conditions that prevailed during evolution, and these, too, are much better understood for vision than for our other senses and cognitive and behavioral attributes. Although about half the brain may be used for vision, much more than half of the best understood parts of the brain involve vision, making vision part and parcel of any worthwhile attempt to understand the brain.

And who am I, in addition to being a square, stick-in-the-mud, pencil-necked cable viewer? I’m a theoretical neuroscientist, meaning I use my training in physics and mathematics to put forth and test novel theories within neuroscience. But more specifically, I am interested in addressing the function and design of the brain, body, behaviors, and perceptions. What I find exciting about biology and neuroscience is why things are the way they are, not how they actually work. If you describe to me the brain mechanisms underlying our perception of color, I’ll still be left with what I take to be the most important issue: Why did we evolve mechanisms that implement that kind of perception in the first place? That question gets at the ultimate reasons for why we are as we are, rather than the proximate mechanical reasons (which make my eyes glaze over). In attempting to answer such “why” questions I have also had to study evolution, for only by understanding it and the ecological conditions wherein the trait (e.g., color vision) evolved can one come to an ultimate answer. So I suppose that makes me an evolutionary theoretical neuroscientist. That’s why this book is not only about four novel ideas in vision science, but puts an emphasis on the “evolution” in “revolution.”

Excerpted with permission of the publisher, BenBella Books, Inc. All rights reserved.

Mark Changizi is Professor of Cognitive Science at RPI, and the author of The Vision Revolution (Benbella, 2009) and The Brain from 25000 Feet (Kluwer, 2003).

[Some related pieces in ScienceDaily: visual computer, “x-ray” vision, color empath, letter shaped like nature, illusions of future]

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To get my blog started, here is a short piece I had written for ScientificBlogging.com about my new book, THE VISION REVOLUTION (Benbella Books, June 2009):

Your color vision is not for seeing red sunsets or green grass; rather, it evolved as a kind of empath sense, optimized to detect the changes in blood physiology in the skin of the faces (and rumps) of others, thereby sensing their emotions. Your forward-facing eyes are not for seeing in depth, but, rather, for significantly enhancing how much you can see in the cluttered forest habitats of your ancestors. Perceptual illusions are not errors your visual system makes in trying to make sense of three-dimensional scenes, but, instead, are due to your brain attempting to foresee the near future, so that by the time the brain generates a perception – which takes a tenth of a second – your perception is of the present. And you have the ability to read not because you’re an especially smart ape (no offense), but because writing has culturally evolved to look like nature, just what your ape visual system is good at processing. My new book – THE VISION REVOLUTION (Benbella Books, June 2009) – is about these four stories; about why we see as we do; about our evolutionary origins; about how our visual capabilities mesh with the world around us. It is about the visual powers you never knew you had.


In the book I also implicitly make a broader point about scientific progress in understanding the brain. Outsiders to the cognitive and brain sciences can sometimes get the impression that we brain scientists have nearly unraveled the riddles of the brain. While it is true that we are making great strides, the real question is, How far away from the finish line are we? Alas, I believe we are nowhere near the finish line; I put my money on several hundred years of brain-slogging left to go. Keep in mind that your brain is more complicated than the rest of the universe combined (minus all the other brains). Truth is, relative to what needs to be known, we don’t know jack.

The reason we have so much work left is that we’re not built like the Arnold Schwarzenegger robot in the Terminator movie. Inside the Terminator’s body – or at least back in a lab where he was designed and manufactured (by other robots) – there are design specifications indicating what all his parts are for. If the Terminator were to become curious about what one of his brain parts is for, he could just gander at the “user’s manual” wherein all his capabilities are enumerated. And many of the Terminator’s perceptions have transparent functions, because his perceptions are often explicitly labeled with what they’re for (e.g., “body-heat sensing camera activated”). Our brains aren’t nearly as scientifically friendly as the Terminator’s. Try as you might, you’ll find no user’s manual in our heads listing our capabilities. You’ll just find gray meat of questionable palatability. And when we perceive, we do so without the benefit of internal written labels explaining to us what the perception is for. Evolution didn’t select us to have user-friendly parts; we weren’t designed to wear our functions – our powers – on our sleeves. What is missing in our understanding of the brain is this enumeration of our functions. Put simply, we don’t even know what we humans can do! And if we don’t know our powers, then we don’t even know what we need to explain. You can’t figure out how the brain carries out X if you don’t yet know we can do X!

The four stories in my book are, as I mentioned earlier, about four powers we didn’t know we have: color is an empath power like that of the annoying Deanna Troi character in Star Trek; forward-facing eyes gives us a kind of “x-ray vision” power to see much better in cluttered habitats; illusions are the signature of our future-seeing power which allows us to perceive the present; and reading itself is a power, only made possible via a clever strategy culture used to make writing easily absorbable by our illiterate visual system. These four heretofore undiscovered powers fundamentally change our view about what our brains can do, and consequently lead to fundamental shifts in the questions we must ask about the underpinnings in the brain. But if these fundamental human powers have only recently been uncovered, one can only imagine the teems of powers that are waiting to be discovered! The brain sciences are filled with brilliant people, but most are not looking to answer such “why” questions. I hope that THE VISION REVOLUTION will excite more people to set their eyes on discovering our enigmatic powers. Only then will we understand what needs to be explained in the brain, a necessary step toward an eventual “brain revolution.”

Mark Changizi is Professor of Cognitive Science at RPI, and the author of The Vision Revolution (Benbella, 2009) and The Brain from 25000 Feet (Kluwer, 2003).


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