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    Alien Vision Revolution (Halloween Edition)
    By Mark Changizi | October 26th 2009 01:27 AM | 22 comments | Print | E-mail | Track Comments
    About Mark

    Mark Changizi is Director of Human Cognition at 2AI, and the author of The Vision Revolution (Benbella 2009) and Harnessed: How...

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    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. 

    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. 

    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.” 

    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. 

    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. 

    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. 

    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.

    Comments

    1) its really stupid to completely rule out color vision in aliens(or completely rule out anything for that matter), the best you can assume is "most likely not". also black and white are still colors, are you suggesting they would survive on other senses alone? without eyes?

    2) your focus on the leafy habitat eludes me, eye structure and quality would have more to do with how close or far they are from their star i think

    3) illusions are nothing but deviants of light in a way, i assume if their eyes were as easy to trick as ours they would have them, but why even pose this question?

    4) many species communicate seemingly telepathically, ants, bees, etc, if a more advanced civilization was to adapt that sort of ability they would have limited use for writing

    He said, "our color vision," not "color vision." He was only referring to whether or not they will see color in exactly the same way we do. For example, the may see a very diverse range of purples with poor sensitivity to other colors or perhaps they are so sensitive to one particular shade that our trees scream green at them like hot pink. You might want to re-read the article.

    Gerhard Adam
    The only question I have is regarding the "forward facing eyes" since this is also a requirement for binocular vision.  Therefore, wouldn't it also be true that such an adaptation is necessary for any alien that would have a need to accurately gauge distance (as predators do)?

    Mundus vult decipi
    Mark Changizi
    Hi Gerhard,

    There are several problems with the predator hypothesis, including...

    (1) Most fish, reptiles, amphibians, birds, and many dinosaurs were or are predators, and yet all had or have very sideways-facing eyes (by mammalian standards).

    (2) Among mammals, the smaller predators like weasils have more sideways-facing eyes than the larger predators, consistent with the prediction of my hypothesis.

    (3) The most forward-facing animals on Earth are some of us primates, which are mostly herbivores, and at best opportunistic predators.

    (4) Stereo is one of the weakest cues to distance, being found to be trumped by other cues such as parallax, real-world-knowledge, accommodation, vergence angle, and position on the horizon. In other words, animals have plenty of other cues.

    (5) One big problem with theories relying upon stereoscopy is that they cannot say why having a more 3D stereo up front is worth the cost of becoming *completely blind* behind. My theory has just one "currency" that is optimized: maximize how much can be seen.

    (6) People who have lost an eye do amazingly well in modern society, and it has been difficult to actually get data showing that they have more accidents, and so on.  Many one-eyeds even are very efficient at piloting sea craft and taking over other ships and their treasure.


    Sincerely,

    Mark
    Gerhard Adam
    Thanks Mark

    One thing that came to mind with your response is to also consider whether or not the predator might also be subject to predation.  In those cases, it would seem that a blend of the two approaches might be in order from an evolutionary perspective.

    In particular, it seems that when a predator is necessarily fast moving that the need for more accurate binocular vision might play a role.  In other words, my personal speculation is that there may be multiple reasons for such forward facing vision, although they bear similarities among animals that have a quite varied existence.

    Am I going down the wrong path?

    Thanks

    Gerhard
    Mundus vult decipi
    Mark Changizi
    Hi Gerhard,

    On fast movers needing more accurate stereo vision (which is what I think you're suggesting), I'd say the opposite -- that when you're fast, you get tons of parallax via your self-motion, which is a much more informative stereo signal than stereoscopy. So you need stereoscopy even *less*.

    As for predators who might themselves be under predation, I'm not sure how that would help explain the nearly universal sideways-facing eyes across predator fish, reptiles, birds and dinosaurs.

    And, as for whether there may be, in fact, multiple reasons for forward-facing eyes, rather than just the one I suggest...maybe. If you look at my paper, and the plots, of course it is not the case that my hypothesis explains all the variance out there. There's plenty of room for secondary hypotheses to explain this.  But I am arguing that the principal selection pressure across animal life for where the eyes are pointed concerns "seeing the most", not stereoscopy or predators or leaping or etc.

    Sincerely,

    Mark
    Gerhard Adam
    As for predators who might themselves be under predation, I'm not sure how that would help explain the nearly universal sideways-facing eyes across predator fish, reptiles, birds and dinosaurs.
    Sorry if I wasn't more clear.  My point was that in this case, they would have a wider field of view and therefore have a greater possibility to see a potential attacker than with the smaller binocular vision.  This was actually based on the predator (narrow stereoscopic vision) and prey (wider field of view) concept.  So I was suggesting that the side facing eyes would allow for such predators to be able to cover a wider range.  In the case of herd animals, this would be a much greater overlapping phenomenon since so many other animals are also present to give warning, but such wouldn't be the case with reptiles, fish, and amphibians.
    Mundus vult decipi
    Gerhard Adam
    Sorry Mark.  I just realized that my comments are essentially based on the same idea as your hypothesis; "seeing more".  Soooo .... nevermind :)
    Mundus vult decipi
    Mark Changizi

    If a predator is also predated upon, then the predator-prey hypothesis would predict some kind of intermediate-level of binocular convergence.  No?  If that's the prediction in that case, then it would seem hard to reconcile with predator fish, reptiles, dinosaurs and birds, where it seems that there's no correlation between how-high-in-the-food-chain and how-forward-facing-the-eyes (e.g., even big shark have almost totally sideways-facing eyes).

    I also note that one of the most dangerous things for any species is others of its own kind, especially when you're little, and even when you're an adult. E.g., lions, a predator that would be a candidate for one that has little worry about being predated upon, mostly gets killed by other lions. Not seeing behind oneself is potentially a big danger.

    (Herd animals, by the way, do have sideways-facing eyes.)

    Sincerely,

    Mark


    Gerhard Adam
    Mark

    Thanks.
    (Herd animals, by the way, do have sideways-facing eyes.)
    Yes, that was my point.  By having a larger field of view, they would have a better opportunity to see whether any threat was approaching.  In the herd, by having that many more animals, the coverage would be quite extensive.

    I realized after I said that, that it involved "seeing more" which was precisely the point you were making.

    Gerhard
    Mundus vult decipi
    Mark Changizi
    My comment came in to fast.

    Thanks again,

    Mark
    Fascinating article... I'm curious about one thing, how much do various animals rely on their eyesight for hunting or related activities? It seems to me that eyesight is almost an afterthought with many animals for the acquisition of food. It would appear that aquatic animals have the least reliance on their visual systems for hunting, and even most land animals seem to rely on vision only in the terminal phase of hunting. In most cases, they seem to use smell/taste and other unique senses (sharks detect changes in the magnetic field) to locate prey.

    I also read somewhere that there are at least 46 unique eye designs here on Earth. Examples of parallel evolution, and those are just the ones still in use. With 46 current designs, and countless obsolete designs, it would seem the sky is the limit to what can be seen and how.

    I think it seems logical that the environment an animal develops in would influence the placement of the eyes as well as what the eye is designed to "see"... just my random thoughts...

    sorry, but i would have to say that this a very perculiar topic.
    i think that a report proving the existence off aliens should be done first then this one linked to it.
    otherwise i suppose its an interesting topic, its just that if someone doesn't have reason to believe there is an alien then the alien will not exist thus not have sight....

    Gerhard Adam
    Mark

    Maybe this is off the track, but do you think that eye placement may relate to how the brain processes information?  In other words, the closer the eye placement, the more cross-over there is between right/left brain information and the convergence of such data (i.e. greater analytical capability)?

    The farther the eyes are apart, the more separate each hemisphere's processing and experience occurs.

    While this might initially sound a bit far-fetched I was thinking about it, because in training horses (i.e. sensitizing them to movement), one has to ensure that the activity occurs on both the right side and left side of the animal.  Otherwise despite having spent 15-20 minutes getting them used to a movement on the right side, that knowledge isn't directly shared with the experience for the left side.  So there's always a certain symmetry required in training to ensure both sides gain the experience.

    Similarly, that lead me to wonder if the point of "handedness" (right or left) was perhaps an artifact from a more primitive ancestor that had exactly such a hemispheric separation in brain activity.

    Anyway ... just some speculative questions.

    Gerhard
    Mundus vult decipi
    Mark Changizi
    Great set of questions, Gerhard. My own guess on whether binocular convergence affects more-general brain capabilities would be that it does not. Large binocular fields mean more cross-over, but only visually.

    Interesting about the horses, and the handedness issue is a mystery to me. My own guess for handedness would be that there's some actual behavioral advantage to having a dominant side, but no real idea.

    Mark
    Hfarmer
    Very interesting article.   I had always heard that the reason we see red so well was because red is the color of so much ripened fruit.  Similarly that seeing green allowed us to see the freshest leaves and shoots.  Could it be a combination of the feeding reason for color vision, and the social reason.  I mean you can't tell a white lie in the Paleogene epoc....because no primate yet had speech.  OTOH, seeing those cues could be more important when one does not have speech. 
    What are your thought's on an aquatic alien?  Would complex life on Europa, with no sun light, have use for eyes at all?  Or perhaps an eye which can sense some other band of the spectrum than our eyes can? 
    Science advances as much by mistakes as by plans.
    Mark Changizi

    Thanks for the comment, Hontas. Fruit and leaves are indeed the main alternative theory, and although both food and skin/emotions could have been part of the evolutionary history of color, only the latter appears to nicely explain why our color is of that specific type (i.e., with our peculiar variety of cone sensitivitiies, which are just right for sensing oxygenation modulations in the blood in the skin). And on aliens with no sun light, certainly one might imagine them evolving sensors for other bands that might be emitted on their planet, if important to them. But I certainly don't know!

    Mark
    Hfarmer
    After I wrote the question I thought of a figure from "Classical Electrodynamics" by John David Jackson.  It shows the dispersion curve with respect to frequency for water.  There is a dip, right in the wavelength's which represent visible light.  
    The professor who first told me this speculated that to see in a wavelength other than near infraed-visible-near UV a creature would have to develop a non-water based eye.  Imagine the possibilities.  
    Science advances as much by mistakes as by plans.
    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.

    Is this quality unique to vertebrates and animals with a CNS or is it more widespread?

    If an animal is moving quickly, like a cheetah, dolphin or bird, is this 1/10 anticipation increased?

    Bonny Bonobo alias Brat
    I have already added this link somewhere else on Science 2.0 but its probably more appropriate here. Someone has put together a pretty amazing YOUTUBE collection of illustrations of UFOs and aliens made by cavemen to modern day photographers at http://www.youtube.com/watch?v=wKGg4E_E-Bo&NR=1&feature=fvwp
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    SynapticNulship
    YouTube in all caps? That must be serious science.  BTW, Erich von Däniken called--he wants you to join him in 1968.  Just take some drugs and step into the Stargate...
    SynapticNulship
    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.
    Indeed, are there any veridical perceptions?