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jsshouldbeworking t1_iwurz22 wrote

To understand the way they "see" things, you can re-frame what you think eyes "do."

Eyes take what is in the world and translate it into something the brain can understand. Chameleons probably perceive the world just as the world is--their brain makes a map of what is 'out there' based on the light that falls on their eyes.

By the way, you own eyes do the same thing. You don't see the "input" to your eyes. You see the map of the world that your brain makes from the input. For example, you don't "see" your nose, even though it takes up a bunch of visual space in each of your eyes' visual input. (Close one eye and look for your nose to check!)

You also don't see details in the world except for a tiny fraction of your vision (the "fovea" in the center of your visual field). Want to check: hold your hand out at arms length and look at your fingernail and without moving your eyes, try and describe any detail on one of your other fingernails. You will likely discover that you can't. You cant even see details a few inches from what you are looking at. Whenever you look at something, you are looking with your fovea. Everything else outside of the fovea is "blurry" and much less colored. You mind fills in the blanks and you end up perceiving the world as clear an detailed.

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SkyKnight34 t1_iwv1rmp wrote

This is really good. I think depth perception is another good thought experiment that illustrates this. Imagine explaining to a chameleon how we use the differences in parallax between each eye to estimate depth. We're not consciously doing trigonometry to determine how far away things are, we can just tell. It's baked in to the map of the world our brain generates from the signals.

Chameleons moving their eyes independently is the same for them, it just looks normal. Their brains are adapted to process a different variety of signals than ours. It's just hard for us to "picture" it, since our vision has some different underlying assumptions built into it. But ultimately, it's probably a decent assumption to imagine that they "see things" the same way we do, just with a worse depth perception and a wider field of view.

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jsshouldbeworking t1_iwvhp1y wrote

Yes!

And if you have ever seen a skink/chameleon/lizard bounce up and down (looks like doing pushups), they are doing the same thing that we do with our two eyes. They move their head to two different positions, and use the paralax to figure out what is in the 'depth' dimension. (Some people also say that they do this in courtship or for displays of dominance, which could also be true.)

It's like the GIFs that alternate between two perspectives to show depth, like this

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dupe123 t1_iwvnd7e wrote

In spanish, pushups are called lagartijas, which comes from the spanish word for lizard (lagarto).

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VivendusMoriendumEst OP t1_ixkmsbc wrote

I'm in an extra different situation in a way. I'm aphantasic (can't imagine/picture/recall visual stuff, nor taste, smell, touch, or otherwise, though my faculty with audio is extraordinary and from what I can tell far beyond typical (I'd trade some for vision tho...)

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SkyKnight34 t1_ixkrjgs wrote

It's so fascinating how our brains have such a variety of abilities, isn't it? It makes me wonder how it affects the way we function in general. Like I know that the way I think and conceptualize things is strongly informed by visualizations. And I'm sure that visualization lends itself more toward certain concepts than others, by its nature. It seems like you probably do the same thing with audio, and I'm sure that that lends itself more naturally toward a slightly (or maybe significantly) different set of representations and ideas. It's just so interesting to consider how we're both looking at the same world through these two different lenses, and probably notice very different things about the world because of it.

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aggasalk t1_iwwk6lt wrote

> Everything else outside of the fovea is "blurry" and much less colored. You mind fills in the blanks and you end up perceiving the world as clear an detailed.

I'm sorry, but you have hit a nerve... This stuff is not really true. It gets repeated over and over again (including, sadly, in undergrad psych and even perception classes...), but.. peripheral vision supports color vision just as well as foveal vision (in fact, better in some ways: there are no S-cones in the fovea!).

And "blur" is a very vague term here. Peripheral vision has lower resolution. But it has a precise resolution, and you see things at that resolution, exactly as you do foveally. But we don't say foveal vision is "blurry", even though it has limited resolution just as the periphery does.

You can see smaller details foveally than you can see peripherally, that's the right way to think of it. But things can appear sharp (or blurry) in fovea or periphery.

e.g. see:

http://anstislab.ucsd.edu/files/2012/11/1998-Peripheral-acuity.pdf

https://journals.sagepub.com/doi/full/10.1177/2041669515613671

https://core.ac.uk/download/pdf/82257353.pdf

https://academic.oup.com/nc/article/2021/1/niab006/6290438

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jsshouldbeworking t1_iwxsfal wrote

Thank you for the references! It's good to have more precise ways of talking about the drop in acuity.

Yes, "blurry" is a vague term. To do all of vision in 2 paragraphs, some things get glossed over.

Sorry I hit an optic nerve. ;-)

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A_Notion_to_Motion t1_iwvg3o0 wrote

>You see the map of the world that your brain makes from the input

Which totally makes sense and doesn't seem strange at all until you start thinking about it as an actual image. When I open my eyes I see the world around me, that tree over there is an actual tree that I'm staring at from a distance. But in another sense it's not the world out there at all but an image of it. So that tree over there is actually an image of a tree "right here". In fact everything we see is an image that is made "right here" next to all the other images that we make. But where exactly is that image? What is it made of, how big is it?

So many weird questions come up when thought about from that perspective.

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louploupgalroux t1_iwvqvn9 wrote

I remember my city's science museum had an exhibit on optics. There were goggles you could wear that would simulate eyes of different animals while you walked around some obstacles. It took some time to get used to.

The horse goggles were really trippy. Couldn't see in front, but could see wide on the sides.

Fun project for any DIY scientists out there that want something neat to bring to parties.

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VivendusMoriendumEst OP t1_ixkn5f1 wrote

Uh TBH I'm specifically about those goggles though field of view and stuff can be simulated I'm a bit unconvinced we really understand animal (or even human) senses and qualia that well, but cool exhibit!

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Micahzz t1_iwvveja wrote

The Kantian idea of transcendental idealism describes this pretty well in my opinion.

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WalkerBRiley t1_iwvs8hp wrote

> You cant even see details a few inches from what you are looking at.

I mean this is untrue for the most part. I can tell you the hat on the stand twelve inches to the left of my focal point is blue. The lunch bag further is black. I can tell you what's on my other monitor.

I can't give you words or tiny details but to say I can't 'see any details' is just false. Our peripheral vision does a really good job at constructing a basic idea of our surroundings even when not focused on them. We'd never have survived if it didn't.

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Sharlinator t1_iwwjwgr wrote

Eh, that's just arguing about semantics, using a different definition of "details" than the GP. And note that many of the details you see in the periphery, your brain simply reconstructs from having previously looked there (and indeed continuously and subconsciously moving your eyes in saccades, collecting a patchwork of detailed information for the brain to stitch into a whole), including colors. You'd be surprised how many of the colors you see in the periphery are entirely filled in by the brain.

From a survival perspective, our peripheral vision mostly needs to do one thing and it indeed does it well: detecting moving things. The moment there's unexpected motion detected, we instinctively shift our gaze there to take a better look with the foveal part of the retina.

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badgerj t1_iwxiw67 wrote

Thanks. That was really cool and insightful. Even as a Scientist, this was really well done! Take this!

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[deleted] t1_iwu7ftp wrote

[removed]

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Nine-Eyes t1_iwu8xlf wrote

Yeah, that's a human brain evolved to use parallax for depth perception, but how does a chameleon's visual cortex work differently with those independently-operated eyeballs?

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Iron_Rod_Stewart t1_iwufuok wrote

We don't know what a chameleons inner life is like, but imagine you're in a dark cave and are feeling both sides of it with your hands. They move independently but you're still able to form a pretty good idea of what the space around you is shaped like.

People think of binocular vision as a series of static images we have to integrate before using them, but it's really more of a stream of information we can use on-the-fly as in the cave example.

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Apokolypze t1_iwud2f6 wrote

This works with both eyeballs pointed in generally the same direction, but a chameleon is capable of pointing it's eyes in completely separate directions and controlling both individually. This isn't really a comparable scenario, right?

The question is whether we know how a chameleon "sees", not how humans see.

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Jewrisprudent t1_iwv5tqj wrote

And the point is that the image you see after the paper is placed there is an image constructed by two images that no longer have any overlap. What you “see” as far as your brain concerned is not so much an image, but a construct of where you are in the world around you. A chameleon is just able to gather information about is surroundings from a functionally wider area, and then their brain process that and they form an understanding of where they are and what’s around them.

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HDH2506 t1_iwun262 wrote

Would VR be valid enough for you? One eye sees Moskva and one eye sees London

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Orisitabagel t1_iwupc9u wrote

Fun fact. If your eyes don't work together you see like this all the time because your brain ignores one eye constantly. So you see two different images with both eyes.

Source: my own personal experience cause for some reason or another my brain never developed the ability to see with both eyes at once and reform the separate images into one. So it decided to constantly ignore one eye. It's like being blind in one eye all the time. But I can still see out of both. I can "switch" to seeing out of one eye or the other. Weird.

So I'm a chameleon?

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Corrupted_G_nome t1_iwvigdt wrote

Humans actually have dominant eyes like dominant hands. Its hard to notice unless there is a case like yours. People who have different prescriptions per eye with glasses have two different images depending which eye is dominant in that moment. Closing one eye over the other I have different levels of clarity/blurryness but when both are open the default is my dominant eye's prescription.

To test a peson can hold their arm out stright forward then close one eye or the other. One eye when closed will cause the image to shift and the other eye when switched will show your arm where it is when both eyes are open.

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Orisitabagel t1_iwvjjnm wrote

Ah that is cool! I never knew about dominant eyes. What you described is my case exactly. Different prescriptions for each lens in my glasses, and the image shifts a bit to the left or right when I change which eye is covered. I usually default to my left eye even though it is apparently the weaker one.

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AllAboutTheData t1_iwv6691 wrote

Another experiment would be to hold a mirror up to each of your eyes. Angle them off to the side so that each eye sees a completely different field. It could be done with a reflective surface, such as a sleeping cell phone, held up to one eye and one hand placed as you described.

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hawkwings t1_iwulsdn wrote

I read that they judge distance by focus instead of using binocular vision. Their eyes can be focused for different distances and they know what distance it is focused for. They need to know the distance to use their tongue attack.

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microwaffles t1_iwvexmz wrote

My understanding is that they change to stereoscopic vision when focusing on prey. I didn't realize they can judge distance using a single eye, thats impressive.

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Corrupted_G_nome t1_iwvho87 wrote

To be fair tho they do miss sometimes and get confused as to what they are looking at. They prefer to face foods directly and use both eyes if they can. They seem to get really focused in on their foods.

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aggasalk t1_iwwiw29 wrote

We do not really know, most of the answers you're getting are very improvised..

Here's something we do know: The chameleon visual system is a bit unusual in that the optic nerves do not obviously lead to common targets in the chameleon brain. (detailed ref on this: https://www.karger.com/Article/PDF/113633)

In most animals where there is some amount of binocular overlap between the two eyes - in humans for example this overlap is huge (the two eyes' views mostly overlap). If you look at where the neural pathways from the eyes lead in the brain, they quickly (after just a couple of synapses) converge on common targets, meaning that neurons in corresponding retinal positions lead to the same neurons in the brain.

This is the fundamental reason why what we see with our two eyes feels so integrated: it is more-or-less the same neurons in the brain handling inputs from both. It's not that the brain "does something" to integrate the inputs - it's simply that the inputs are largely handled by the same neural mechanisms. In fact, you don't even have conscious access to individual-eyes views (if I poke a neuron in one of your eyes, you'll see a flash - but you'll have zero idea which eye it was in).

For the chameleon this isn't obviously true. Outputs from its two eyes are segregated well into its brain: one optic nerve goes to one nucleus on one side of the brain, the other optic nerve goes to the other side (our optic nerves split apart after they leave the eye, and merge into two "optic tracts" leading into the brain, each representing the same side of the visual field, half of each tract contributed by each eye).

It's almost certainly true that if you follow the chameleon's visual pathways far enough, deep enough, they'll meet eventually, but just reading about the basic neuroanatomy, I'd guess that the chameleon's visual experience is of two largely-segregated eye-views, which sometimes include common content, which the chameleon "knows" (to whatever extent you can say a chameleon "knows" things) are the same, thanks to the fact it does have some neural convergence of those inputs, somewhere deep in its little lizard brain.

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VivendusMoriendumEst OP t1_ixknugu wrote

Ok this is the sort of comment I love reddit for, especially askscience!

It's very much in line with what I've gathered myself but your insights on the actual neuroanatomy is so cool!

Dunno what your field is, but I have aphantasia (inability to form, imagine, recall, etc) visuals , in fact for me I have no mental simulation or recall of any sense but audio, which I have an apparently extraordinary faculty with, to recall or improvise very detailed and complex multi instrument music for example.

Very interested in what's atypical about my brain, this is one part. Finally seeing some research into aphantasia (most recently read an article classifying it as a memory disorder, though it seems I'm extremely rare in having such abilities with audio while no other sense in my mind.

Any ideas?

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Koshekuta t1_iwvizca wrote

I had a bad eye, a lazy eye and at times I would get two images displayed to me at once, double vision. Could those lizards perceive the world similarly? The vision in my bad eye is so bad that everything is blurry from any range but sometimes my brain would display what was in front of my bad eye and overlay it like a ghost image over what my good eye was seeing.

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