Evolutionary advantage of seeing ‘upright’

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    • #16445
      Beany
      Participant

      Hi I feel I should preface this by saying I’m not an academic in any way, I’m just curious. Also I’m slightly sleep deprived and this is the sort of thing my mind turns to. So forgive me if this is all quite trivial.
      Anyway my question is basically what I’ve said in the title; as far as I’m aware, all seeing animals have what we’d term ‘upright’ vision i.e. the ground is beneath them. This combined with the fact our brain corrects the upside down image our eyes actually receive and – according to wikipedia – one study shows that the brain, given time, will even attempt to correct an inverted image if one tries to intervene by wearing glasses that invert everything.* Seems to suggest there’s some benefit to seeing the world this way.
      However, I can’t fathom why this would be. The fact it seems to apply to all animals would imply it’s quite a useful trait. All I could think of was that there’s some sort of outside property (like gravity for a bad example) that would skew the process of evolution in a display of sort of coincidental bias but then that wouldn’t account for the fact our brains seem to have a preferred visual orientation.
      Ultimately, if you’ve managed to trail through my ramblings, I’d be interested to know the answer – assuming there is one of course.

      *http://en.wikipedia.org/wiki/Perceptual_adaptation

    • #110859
      JackBean
      Participant

      It’s useful, because it’s useful to know that the ground is below you and not above. I can hardly think about any creature (even imaginary), which would have ground above (unless we’re talking about animals living beneath surface, but they still have the same organization).

    • #110863
      Beany
      Participant

      Why is it good to know that the ground is below though? After all ones sense of where the ground is would still be the same it’s just the visual perception of it that’d be different.
      Also, in the Wikipedia entry, it notes that when you invert someone’s vision they’re able to function perfectly fine.

    • #110864
      canalon
      Participant

      Or since you are talking a bout perception, is it really what we think it is. Our brain generate an image of the world that fits our perception so that I am used to that vision. As you say if it was inverted by special glasses, your brain would try to correct its visual perception to match the rest. But since it is only a perception, it does not matter how the image in the brain is being built as long as it is perceived as a coherent whole.

    • #110869
      Beany
      Participant

      Yes ultimately which way up we see is irrelevant but this is my point; it’s peculiar that our brains would opt to waste energy flipping the image received by the retina when leaving it as is wouldn’t seem to be an issue.
      I can’t imagine that if the human race had developed seeing the world upside down we’d be any different. However there must be some benefit to perceiving the world this way. I suppose it’s possible that this is just an evolutionary remnant of some sort.

    • #111150
      Rap
      Participant

      LOL – this is a fascinating question. The bottom line is that there is no such thing as "seeing upright" versus "seeing inverted". To see this, suppose you have a person who sees upright and another person who sees upside down. Since birth. Now try to devise an experiment to determine which is which. You cannot do it.

    • #111157
      JorgeLobo
      Participant

      How do we know how all animals see/perceive the world visually? Not challenging – just curious.

    • #111172
      animartco
      Participant

      Hi Beany. Interesting question. I think it has something to do with the convex shape of the retina. The camera also has an upside down image. However this doesn’t explain why the brain changes it. Except that our orientation is with the ground beneath. We can’t walk on our heads. However we could walk as easily if we saw our feet and the earth, above us. Hey this is a really good question! Why should the brain go to the trouble of reversing the image? What possible advantage could their be to seeing the earth beneath us instead of above? It might be something to do with left right orientation and the earths magnetic field.

    • #111176
      Darby
      Participant

      It might be associated with actions associated with gravity – a lot of reactions anticipate the downward motion of objects.

      Or maybe we just ASSUME we’re flipping the image – it’s all just processing, after all.

    • #111183
      OdinsRaven
      Participant

      This is an excellent question. Like you said, why would the brain "waste" energy if it wasn’t important? I think we should really examine what Darby said first. What evidence is there that the image is flipped?

    • #111185
      Rap
      Participant

      This question is so interesting because the answer is not what you might expect at first glance. Your brain does not "flip" the image. As Darby said, it simply processes it. I think newborn babies haven’t learned to process it yet. If you fitted a newborn with image-reversing glasses, they would learn to process it properly. Then, when they grew up and you had two adults, one with glasses, one without, you could never figure out which had the glasses and which did not by asking them questions, (except questions like "are you wearing reversing glasses"). I mean, any question you asked them about which way was up and down, you’d get the same answer. Ask them if their image is "reversed" and they would both say no, it looks fine. There is no "up" or "down" other than what you have learned. Their experience will be the same. If you took the glasses off the one person and put them on the other, then both would see things upside down.

    • #111200
      EmperorSunshine
      Participant

      Hypothetical question: Let’s say I hoisted you upside down by your feet, and asked you to point "down." Would you point towards your feet or your head? If vision is "upright," so that "down" always corresponds to the lower part of your vision (like you’re saying), then you should point towards your feet (even though most people would call that "up"). On the other hand, if down is defined as the direction that gravity is pulling you (vestibular sense), then down is towards the Earth, which is the opposite of "upright vision."

      What I’m getting at is that your central assumption is wrong – vision isn’t upright. What it actually is is integrated with your other spatial senses, specifically hearing, touch, and the vestibular sense. This "integration" process happens in the angular gyrus, a part of your brain located between the visual and motor cortices. You only assume your vision is upright because under normal circumstances all your senses are in agreement with your intuitive notion of what "down" is supposed to be.

      Alternatively, imagine what it would be like if your vision was NOT in agreement with your kinesthetic senses. You would be able to see things, and recognize what they are, and see how they are positioned relative to each other, but you wouldn’t be able to do very much with that information. If a predator was running towards you, you wouldn’t know which direction to run in order to get away from it (as opposed to running closer to it). You definitely wouldn’t be able to catch a baseball, or pick up a fork, or do anything that involved using vision to plan an action.

      I suppose what I’m getting at is that a) you define "down" in terms of your senses and b) your senses should be in agreement with each other so you can form a coherent mental model of the world, therefore c) therefore down is usually whatever your senses tell you it is.

    • #111211
      Rap
      Participant

      EmperorSunshine is right. It’s not a question of which way is up, its a question of whether your vision is in accord with that part of your brain that tells you how to move. When people are fitted with image-reversing glasses, eventually they say that the image has righted itself. That’s something you could theoretically test for – does their brain rewire to invert the already-inverted image from the optic nerve, or does that part of their brain that tells them how to move rewire itself?

    • #111216
      animartco
      Participant
      quote Rap:

      This question is so interesting because the answer is not what you might expect at first glance. Your brain does not “flip” the image. As Darby said, it simply processes it. I think newborn babies haven’t learned to process it yet. If you fitted a newborn with image-reversing glasses, they would learn to process it properly. Then, when they grew up and you had two adults, one with glasses, one without, you could never figure out which had the glasses and which did not by asking them questions, (except questions like “are you wearing reversing glasses”). I mean, any question you asked them about which way was up and down, you’d get the same answer. Ask them if their image is “reversed” and they would both say no, it looks fine. There is no “up” or “down” other than what you have learned. Their experience will be the same. If you took the glasses off the one person and put them on the other, then both would see things upside down.

      Hi Rap. You make a very good point. Does our image actually flip? Does the brain actually turn the image like a single lens reflex, rather than a box brownie? I think it does. There are cases where a blow to the head can reverse the image temporarily, which suggest that when the brain is working properly it DOES flip the image. Yet none of the explanations given as to why it is easier to function with a flipped image hold water. There must be a proper explanation. What is it?
      here is an interesting thought. Perhap it’s cultural? Nowadays we know that we are held onto a planet that is floating in space, by gravity. Therefore if the image was reversed it wouldn’t interfere with our weltenschauung. Primitive man beleived the world was flat and that if you were to go to the edge of it you would fall off. a reversed image would possibly compromise this point of view. In other words if the image had remained reversed we would never have ended up believing what we do now. Our whole culture would have run along different lines. Just a thought.

    • #111224
      Rap
      Participant

      No, I think the answer is subtle and hard to explain. Your brain does not flip the image, it simply deals with it. Your brain does not see the image and say "thats wrong, I must correct it". Your brain doesn’t know that its "wrong". The subtle part is that there is no "right" or "wrong". Your brain simply deals with the image, and in so doing, you get a sense of up and down. Its only when you look at someone’s retina and see that the image is reversed that an apparent problem occurs. If you were to program a robot with an eye and a hand, you wouldn’t first reverse the image. You would simply write a program that dealt with the image and the hand. Its almost like saying "no, your brain doesn’t reverse the image, it simply tells your hand to move the wrong way". But that assumes right and wrong, and so its not correct. Your brain is a bunch of neurons feeding it input. Your brain’s sense of up and down is determined by that input, and how it has learned to deal with that input. It has no understanding beyond that of what is up and down, and doesn’t need any, and, more subtly, none exists.

    • #111226
      TheSunshineEmperor
      Participant
      quote animartco:

      Does our image actually flip? Does the brain actually turn the image like a single lens reflex, rather than a box brownie?

      There is no "image." Your brain isn’t like a television. It directly processes the signals coming in from your optic nerve – at no point does it try to reconstruct what your retina is seeing.

      If you’re interested in this, the vertebrate visual system is one of the best studied and best understood aspects of neuroscience. There are many great books that explain not only what we know about vision, but also how we know it.

    • #111241
      Darby
      Participant

      Almost everything your brain does in the optic area is process the almost-raw images. Just do a blind-spot test and you’ll see that it reconstructs – and constructs.

    • #111252
      TheSunshineEmperor
      Participant
      quote Darby:

      Almost everything your brain does in the optic area is process the almost-raw images.

      Yes, obviously. Your brain starts with a bunch of signals on your optic nerve (which have only been minimally processed), but ends up with highly processed information. However, none of this actually requires reconstructing the complete image on the retina.

      quote :

      Just do a blind-spot test and you’ll see that it reconstructs – and constructs.

      Wouldn’t this be evidence AGAINST your explanation? If your brain is making inferences about what’s in your blindspot, that suggests it ISN’T reconstructing the actual retinal image.

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