Discussion of everything related to the Theory of Evolution.
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?
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.
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.
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.
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.
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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