Please read my post before commenting.
I’ve heard the elbow thing and the “what do you see behind you” thing a hundred times.
My thought process is that the optic nerve is essentially an HDMI cable. Whether it is connected to a computer that is turned off (a closed eye, if you will) or just completely disconnected (suppose you are missing an eye or something), the signal it sends to the monitor is the same: nothing.
The “monitor”, the visual cortex, as far as I understand, just constantly processes what the optic nerve sends. So if blind people don’t lack a visual cortex, and the signal that cortex receives from the optic nerve is identical to that of a regular person seeing zero light (assume closing your eyes means 0 light, disregarding light seeping through eyelids and whatnot), how can you say that blind people see nothing while we see black?
In: Biology
I think you’re thinking along the right lines, but filling in some blind spots (pun intended) in your knowledge with some good but flawed guesses.
If you’d let me explain my view on it (again, pun intended):
I have Multiple Sclerosis. Im not a “blind person” but i am “blind” in one eye. One of MS’ wonderful characteristics is that it interferes with certain nerves, and one of the cards I was dealt is that I have bouts of Optic Neuritis.
To continue your analogy, my HDMI cable was damaged in a fire. The plastic shroud melted and some of the copper cable inside got damaged too.
The capability of the human body and brain is a remarkable thing, and I’ve repaired the burnt cable by wrapping it up in insulation tape (replacing the cable is not an option)
Although it’s a pretty good fix, I’ve left some gaps in the insulation tape and as a result there’s still some copper exposed. When different parts of my brain get used, (heat, stress, stimulation) then those bits swell and find thier way into the gaps in my subpar repair job.
The effect this has on my AV system is that the HDMI cable suffers a lot of interference. The source and the processor are working fine but the cabling causes data transfer issues. Sometimes the quality is 1080p, but sometimes it’s like looking through a sheet of tracing paper. Light and colour gets transmitted but resolution and focus is miles off what it should be.
TLDR: Im blind in one eye. I don’t see “Black” because my nerves make the best of the hand they’re dealt. It’s not “Black” but it’s nowhere near “vision”
Because our brains are *really* good at cutting down on redundant processing.
If you hear a constant pitch, your ear will eventually tune it out. If all you see is “black” then your brain goes, “well we only get this one signal from eyes and we know there’s nothing there so we can just ignore that and process something else”.
You can reprogram your own eyes if you want. There are glasses that flip your entire field of view upside down. Wear them for a week, and your brain “rights” the field of view such that if you **don’t** wear the glasses you see things upside down for a further week.
According to my one eyed buddy, same thing. Took him about a week to stop seeing a black spot and now he just has a blind spot.
>the optic nerve is essentially an HDMI cable
Ok, what about an HDMI cable that’s cut in the middle or has one or both ends snipped off? Or one where the middle is so frayed that the internals of the wire are exposed? A lot of blindness (or partial/near blindness) is due to the optic nerve not developing properly or not making the right connections. The premise that it’s always a perfect HD cable that is always well-connected on both ends is incorrect.
>**if** blind people don’t lack a visual cortex, and the signal that cortex receives from the optic nerve is identical to that of a regular person seeing zero light
False premise. The signal that my visual cortex receives from my right optic nerve is not at all like what it receives from my left eye when there’s zero light.
On top of that, we know black because we’ve seen it compared to white and other colors. If we hadn’t, you wouldn’t. Without light, there is no darkness.
For instance, you know what it feels like when there are 20kHz radio waves around and what it feels like when there are 20GHz radio waves around, so when you disconnect the antenna that you have implanted in your brain, it must feel like 20GHz regardless of what radio waves are around in the area right? No? Of course not, because you never developed a sensor for radio waves and innate feel for the differences between them.
It’s funny, it’s as difficult to describe as trying to describe a new color. I can’t speak for other people, but during my laser eye surgery when they used the suction to pull my eye out a little I lost all sight in the eye while it was under sunction. It really is the complete absence of vision rather than “seeing black”. You don’t see black, you don’t see white, you just can’t see. The entire sense of sight is gone. (temporarily for me of course)
Okay the best way I have been able to visualize this is by standing at a table, and putting my hands under the table, then I look straight ahead and try to “see” through my hands. My hands are not capable of sending visual information to my brain
“it’s like trying to see out your elbow.” It’s not black, just not there.
There’s also obviously different versions of blind. Some do register light and dark. Some have intense blur. Some have a “hole” in Thier vision. Some believe they can see when they can’t because the brain is registering something but it’s not right… And so on
> the signal that cortex receives from the optic nerve is identical to that of a regular person seeing zero light
Yes, but the *psychological interpretation* of that signal differs from person to person.
A sighted person *expects* to see things at least once in awhile, and thus their brain is geared to pay attention to the optic nerve signal. An environment of total darkness registers as “seeing black”.
A blind person (especially if they’ve been blind for a long time) has no expectation of ever seeing things, so their brain is geared to ignore the optic nerve. This registers as “seeing nothing”.
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