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Please note: I've seen this and this, but my question is different as it is about a single human generation.

If a child was born and raised in an environment with a lack of light, (i.e. a cave, or other underground area) provided they lived to adulthood, what might the repercussions be when they were adults if they were exposed to light? Would their brain have developed itself despite stimulus, or would the person simply be blind?

I am looking for an answer particularly about brain development as far as sight goes, not how pale they would be. :)

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    $\begingroup$ While I appreciate being awarded the answer, in the future you should wait a few solid hours (maybe as long as a day) before awarding the answer so that more people are encouraged to contribute to the conversation. $\endgroup$ – AndreiROM Jan 15 '16 at 19:51
  • $\begingroup$ Okay, just your thing seemed good off the bat. :P i will consider delaying a response in teh future $\endgroup$ – Vince Scalia Jan 15 '16 at 19:52
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The brain develops to better process the stimuli it receives. Since this person would not benefit from the use of their eyes, the brain would not receive visual stimuli, and would not "learn" to process those stimuli.

Would this mean that this person would be blind forever? I honestly have no idea.

But getting out into the light would probably be a very painful experience for them, and they would have a lot of trouble operating in the above-ground world for a long time - maybe this person would never be able to adapt to seeing.

Being able to see may suddenly be terribly confusing, even scary. There would definitely be psychological issues.

I would suggest researching phrases such as "blind person sees for the first time", etc. There must be some studies out there on the issue.

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Assuming that the person in question has (physically) perfect sight, but has yet to see even a small amount of light, their eyes would be about as developed as that of a newborn - that is, blurry and confusing. Try crossing your eyes; it suddenly becomes very difficult to focus on anything. Text that was clear moments ago becomes blurry to the point of illegibility. Your eyes didn't get worse; you just shut off part of your eyes' natural, learned ability to focus.

Additionally, even babies in the womb can sense at least a small amount of light. Not much, but some. For someone who has truly seen no light at all, the light of even a dark night may seem painfully bright at first, and the light of day would be crippling, even with closed eyes. The first few hours would be spent simply adjusting to light in general, without even bothering to make sense of it.

Chances are, after some time of adjustment, they would be able to see, but it would take a long time for them to fully match their known information - the shape of an object based on touch - with the information from their eyes. Tiny babies spend hours a day staring at things, training their eyes; for an adult, that time would be difficult, as most adults would like to do something productive, and staring at a wall or their first for 45 minutes just doesn't seem to be anywhere near productive.

This article should be pretty accurate. Quoting from the article:

The absence of these rules can frustrate the newly sighted, whose visual world can be both blurry and two-dimensional—paintings and people are often described as “flat, with dark patches”; a far-away house is “nearby, but requiring the taking of a lot of steps”; streetlights seen through glass are “luminous stains stuck to the window”; sunbeams through tree branches collapse into a single “tree with all the lights in it.” (The writer Jorge Luis Borges, who went blind at age fifty-five, described going blind as a process by which “everything near becomes distant.” In the newly sighted, without depth perception, the opposite seems true: the distant—tiny houses on the horizon, clouds in the impossibly high sky—suddenly looks nearby.)

Without the rules learned from birth, the newly-sighted have to come up with their own rules - starting with the brain figuring out how far apart their eyes actually are. Without that information, it can't combine the left and right images into a single, 3D image. Still, the brain is an amazing thing, and even the elderly could teach their eyes to see.

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  • $\begingroup$ I can't cross my eyes... but good stuff here any way. :P $\endgroup$ – Vince Scalia Jan 16 '16 at 16:30
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A study shown where a blind person regained his sight:

he could not recognize anything by looking at it, but when he touched it and felt it with is fingers (ie. a fork) he would instantly recognized what it was.

I am willing to bet something similar would happen in this scenario, assuming your human interacted with everyday objects (silverware, pencils, clothing or tools)

Though i think since your person was born WITH sight but never used it, then the eyes would definitely not function as well, kinda refuting everything i just said...

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  • $\begingroup$ A story such as this was made into a documentary a while ago, where a man who went blind from the age of 10 received a bionic eye (some sort of camera-like implant) so he could see once more. He was able to distinguish light/colour but had no "depth-perception", unable to tell how far away an object was, hence he was reliant of a guide-dog to move around, and still does 1 year later; the brain is astoundingly good at adapting to "read" new stimulus though (you can effectively learn to read vibrations against your skin!), so doctors believe this man will learn to function just fine in future. $\endgroup$ – Harry David Oct 5 '16 at 4:11

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