Your blind spot -- cool!!

Most people (even many who work on the brain) assume that what you see is pretty much what your eye sees and reports to your brain. In fact, your brain adds very substantially to the report it gets from your eye, so that a lot of what you see is actually "made up" by the brain.

Look around. Do you see a blind spot anywhere? Maybe the blind spot for one eye is at a different place than the blind spot for the other (this is actually true), so you don't notice it because each eye sees what the other doesn't. Close one eye and look around again. Now do you see a blind spot? Hmm. Maybe its just a little TINY blind spot, so small that you (and your brain) just ignore it. Nope, its actually a pretty BIG blind spot, as you'll see if you look at the diagram below and follow the instructions.

Close your left eye and stare at the cross mark in the diagram with your right eye. Off to the right you should be able to see the spot. Don't LOOK at it; just notice that it is there off to the right (if its not, move farther away from the computer screen; you should be able to see the dot if you're a couple of feet away). Now slowly move toward the computer screen. Keep looking at the cross mark while you move. At a particular distance (probably a foot or so), the spot will disappear (it will reappear again if you move even closer). The spot disappears because it falls on the optic nerve head, the hole in the photoreceptor sheet.
So, as you can see, you have a pretty big blind spot, at least as big as the spot in the diagram. What's particularly interesting though is that you don't SEE it. When the spot disappears you still don't SEE a hole. What you see instead is a continuous white field (remember not to LOOK at it; if you do you'll see the spot instead). What you see is something the brain is making up, since the eye isn't actually telling the brain anything at all about that particular part of the picture.

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Who knew???

I must have done something wrong because it did not disappear with either my left or right eye closed. I went from about 2 1/2 feet away from the screen all the way up to stupid-looking close.

Fisher said:

I must have done something wrong because it did not disappear with either my left or right eye closed. I went from about 2 1/2 feet away from the screen all the way up to stupid-looking close.

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Close your left eye and look at the plus sign with your right eye. Move slowly toward the screen. Should work.

Fisher said:

I must have done something wrong because it did not disappear with either my left or right eye closed. I went from about 2 1/2 feet away from the screen all the way up to stupid-looking close.

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@ 1 foot, with your open right eye directly over the plus does it for me.

MaggieD said:

Who knew???

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I learned about this in High School though, we drew a dot on paper and moved it around until it disappeared.

Lachean said:

@ 1 foot, with your open right eye directly over the plus does it for me.

I learned about this in High School though, we drew a dot on paper and moved it around until it disappeared.

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What's so unbelievable is that you have it everywhere you look -- this little experiment just shows how to recognize it. Our brains "fill in the blank". Remarkable!!

MaggieD said:

Close your left eye and look at the plus sign with your right eye. Move slowly toward the screen. Should work.

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Worked for me.

MaggieD said:

Close your left eye and look at the plus sign with your right eye. Move slowly toward the screen. Should work.

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I think you are punking us, I started again from about 3 1/2 feet away and was in with 6 inches of the screen and went back again slowly just now and it still does not disappear.

MaggieD said:

What's so unbelievable is that you have it everywhere you look -- this little experiment just shows how to recognize it. Our brains "fill in the blank". Remarkable!!

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You brain fills in a lot more than the blind spots. There are some articles about your brain's capacity for simulation on NeuroLogica Blog but they're old, when I can recall the titles ill link some to you if you find this kind of thing interesting.

Or better yet, have you seen that new show Brain Games?

Fisher said:

I think you are punking us, I started again from about 3 1/2 feet away and was in with 6 inches of the screen and went back again slowly just now and it still does not disappear.

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No!! Absolutely not!!! Maybe it has something to do with the size of your monitor or something. Here's the link...see if it works from there:

Blind spots

Fisher said:

I think you are punking us, I started again from about 3 1/2 feet away and was in with 6 inches of the screen and went back again slowly just now and it still does not disappear.

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Don't go forward and back, go left and right when you are ~ a foot away, and of course stare at the + not the dot.

It should be noted that you must cover up one eye and look at the opposite symbol, using your periphery to detect the other symbol disappearing. In other words, look at the plus sign with your right eye and the dot with your left eye.

This occurs because of the physiological blind spot. The cornea (back of the eye) is covered with photoreceptors which detect light. Tightly packed into the center of the eye are cones which allow for color detection and discernment of great detail. Moving towards the outer portions of the cornea, the cones begin to become interspersed with rods until the outer area is filled with nothing but rods. The rods have a larger receptive area which allows for greater light detection (similar to the pupil or aperture of a camera). This area allows you to see better in low light levels. However, the color detection is all but eliminated and details are grainy.

The reason why we have a physiological blind spot (or day blind spot) is due to the lack of cones and rods at the point where the optic nerve connects to the cornea. This point is slightly offset from center which allows for its disappearance due to binocular vision.

However, there is also a night blind spot. This is right in the center of your vision because of the absence of rods in the center of the cornea. To test this, allow your eyes to adjust (or test at night in a dark room) and attempt to look at a small object directly. It will magically disappear. This is why people who work at night are trained to use off-center viewing techniques.

Science is fun!

Nobody tell Fisher that we're actually watching him through a web cam.

MaggieD said:

No!! Absolutely not!!! Maybe it has something to do with the size of your monitor or something. Here's the link...see if it works from there:

Blind spots

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Nope no difference. You are just being a mean girl playing pranks on us little kids. You should be ashamed of yourself.......

or maybe it has something to do with my nerve endings. I know that my dentist has told me that all my brothers and sisters have the same issue I do---when it comes to nerve endings in our mouth we have a zillion more than most people but they are finer so we don't feel pain as intensely as most people but it is very difficult to numb us. No matter what he is doing, we get the needle straight through the roof of our mouths to block the nerves before they branch because he can put the max amount of procaine or whatever it is in our jaws and we can still feel him working on our teeth and I am apparently the worst one of the lot.

Fisher said:

Nope no difference. You are just being a mean girl playing pranks on us little kids. You should be ashamed of yourself.......

or maybe it has something to do with my nerve endings. I know that my dentist has told me that all my brothers and sisters have the same issue I do---when it comes to nerve endings in our mouth we have a zillion more than most people but they are finer so we don't feel pain as intensely as most people but it is very difficult to numb us. No matter what he is doing, we get the needle straight through the roof of our mouths to block the nerves before they branch because he can put the max amount of procaine or whatever it is in our jaws and we can still feel him working on our teeth and I am apparently the worst one of the lot.

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That's just bizarre. You aren't trying to look with your mouth though, are you? :rofl

Maybe you're an alien . . .

X Factor said:

Nobody tell Fisher that we're actually watching him through a web cam.

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:lol: :lol: :lol:

Ever try to lick your elbow??

MaggieD said:

:lol: :lol: :lol:

Ever try to lick your elbow??

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Damn, now I have a near irresistible impulse to try that.

Lachean said:

Don't go forward and back, go left and right when you are ~ a foot away, and of course stare at the + not the dot.

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Nope, no difference. On my monitor, the dot and the cross appear about an index finger apart so maybe it is a magnification issue

MaggieD said:

That's just bizarre. You aren't trying to look with your mouth though, are you? :rofl

Maybe you're an alien . . .

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No but if the nerves are like that in my mouth they probably are inches a way in my eyes.

It is weird. My dentist said he had to learn the technique just for us. Fortunately my next to oldest brother was the trailblazer that encouraged the dentist to pursue using the technique since the second one is a slugger. There were a few times I told him to just do what he needed to do and took it like a man when he couldn't get me completely numb after like 3 or 5 or whatever it was vials of the stuff. I knew he said he legally couldn't give me any more than he had.

The plus side is I can feel things like ticks the second they step on my skin.

You are not alone.

Fisher said:

Nope, no difference. On my monitor, the dot and the cross appear about an index finger apart so maybe it is a magnification issue

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Obviously, we super-humans don't have the same defects as the mere mortals.

Everyone has it. At approximately 12" it will be 3" to the side. It is large enough to hide a 747 at one mile. (Or was it ten miles? I'll have to look it up.)

TNAR said:

Everyone has it. At approximately 12" it will be 3" to the side. It is large enough to hide a 747 at one mile. (Or was it ten miles? I'll have to look it up.)

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Then they are going to have to invent a Specklebang/Fisher proof test because this one sucks if that is true. I am going with the we are superheroes thing until then.....

Fisher said:

Nope, no difference. On my monitor, the dot and the cross appear about an index finger apart so maybe it is a magnification issue

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On my five inch phone they are about an inch and a half apart.

I lose the dot at a couple inches from the screen

TNAR said:

Everyone has it. At approximately 12" it will be 3" to the side. It is large enough to hide a 747 at one mile. (Or was it ten miles? I'll have to look it up.)

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Are you Flying Blind?

Len Kauffman ask this question in the newsletter to his chapter this month. It is something some of us will not admit to but the truth is that we all have a blind spot. Most pilots learn this from their instructor while learning to fly and it is taught in all speed reading classes. The blind spot is about 3/4inch in diameter at one foot from the eye. At a distance of 800 feet, however, it's about 50 feet across and could easily hide an airplane. Move out to one mile and the blind spot is over 300 feet. That's enough to hide a 747.

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Right you are.

Another interesting eyeball fact: most of your peripheral vision is not in color. Your brain fills that in too.