We think we see the world clearly and in real time, but the vision is different
Fix the gaze on the line of text, and don't move your eyes. At the same time try to shift attention to the line below. Then another one. And more. After half a minute you will feel that in the eyes like dimmed: clearly visible only a few words, on which you focused your eyes, and everything else is blurry. In fact that is how we see the world. Always. And I think that we see everything crystal clearly.
We on the retina there is little point at which sensitive cells — rods and cones — enough that everything was normal seen. This point is called the "Central pit". Fovea has a viewing angle of approximately three degrees in practice this corresponds to the size of a thumb nail at arm's length.
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Throughout the rest of the surface of the retina sensitive cells is much smaller — enough to distinguish the vague outlines of objects, but no more. In the retina there is a hole that does not see anything at all — "blind spot", the point where the eye nerve is connected. You, of course, not notice. If that's not enough, then let me remind you that you still blink, that is, shut off the sight every few seconds. What is also overlooked. Though now paying. And it prevents you.
We do something see? The answer is sort of obvious: we quickly move our eyes an average of three to four times per second. These sudden simultaneous eye movement called "saccade". We, too, by the way, don't notice usually, and it's good: as you may have guessed, during saccades vision is not working. But with the help of saccades we keep changing the picture in the Central fovea and eventually covered the entire field of view.
The world through a straw
But if you think about it, the explanation is no good. Take the fist a cocktail straw, put to your eye and try to see the movie — I'm not talking about having to go for a walk. OK seen? This is your three levels of review. Stir with a straw how much of normal vision will not work.
In General, a trivial question. How is it that we all see, if we see nothing? There are several options. First: we still don't see anything — we just have a feeling that we all see. To check whether this is a deceptive impression, we move the eye so that the fovea is centered on the point that we check.
And think: well, you can see everything! And on the left (whack the eyes of the left), and right (back and right). It's like a refrigerator: if we start from our own experiences, then there is always the light.
The second option we see is not coming from retinal image, and quite another — that which builds for us a brain. That is, the brain crawl straw here and there, diligently is from this single image and we perceive as the reality of the environment. In other words, we see not with the eyes but with the cerebral cortex.
Both agree on one thing: the only way to see anything is to move the eyes. But there is one problem. Experiments show that we distinguish objects at a phenomenal rate — faster than the time to react extraocular muscles. And we ourselves do not understand. We think that we already moved his eyes and saw the object clearly — although actually we're just going to do it. It turns out that the brain not only analyzes the picture adopted with the view, it still predicts.
Unbearable dark stripes
German psychologists Arvid Herwig and Werner Schneider conducted an experiment: volunteers were fixing the head and special cameras recorded the motion of their eyes. Test subjects watched a blank screen. Side in the lateral visual field on the screen will display the striped circle, in which volunteers immediately looked.
Here the psychologists have done a clever trick. During saccades vision is not working — man for a few milliseconds becomes blind. The camera caught that subjects started to move the eyes in the direction of the circle, and at this point, the computer substituted a striped circle to the other, which is different from the first number of strips. The participants did not notice the substitution.
Was as follows: in peripheral vision, the volunteers were shown a circle with three stripes, and in focused or Central stripes have appeared, for example, four.
Thus volunteers were trained to associate a vague (side) image of a single figure with a clear (Central) follows the other figure. The operation was repeated 240 times within an hour.
After training began the exam. Head and eyes are again fixed, in a lateral field of view is again taken out a striped circle. But now, as soon as the volunteer started to move my eyes, the circle was gone. A second later on the screen appeared a new circle with a random number of stripes.
Participants in the experiment were asked keys to adjust the number of stripes so as to obtain the figure that they just saw with her peripheral vision.
Volunteers from the control group, which in the learning phase showed the same figures in the side and Central vision, defined "the degree of banding" is quite accurate. But those who were taught the wrong Association, saw the figure differently. When you are learning the number of strips increased, at the stage of examination subjects recognized three-way four-circles as. If reduced, then the circles they seemed dvukhpolosnykh.
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Illusion of view and illusion of the world
What does it mean? Our brain, as it turns out, constantly learns to associate the appearance of an object in peripheral vision with the way this object looks like when we translate a sight on him. And then uses these associations to predict. This explains the phenomenon of our visual perception: we learn the items before, as, strictly speaking, they make out, because our brain analyzes the fuzzy picture and recalls on the basis of previous experience, how the picture looks after focus. He does it so fast that it seems to us clear vision. This feeling is an illusion.
Amazing how effectively the brain learns to make such predictions: in just half an hour of mismatched images in the lateral and Central vision enough to volunteer were wrong to see. Given that in real life we move our eyes hundreds of thousands of times a day, imagine the terabytes of video from the retina the brain of a shovel every time you walk down the street or watching a movie.
It's not even in vision itself — it's just the most vivid illustration of how we perceive the world.
It seems to us that we sit in a transparent spacesuit and drawn into itself the surrounding reality. In fact, we don't interact directly. What seems to us an imprint of the world, actually built a brain virtual reality which is given to consciousness at face value.
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To process information and to build from the processed material more or less complete picture, the brain takes about 80 milliseconds. These 80 milliseconds — delay between reality and our perception of this reality.
We are always living in the past — or rather in a fairy tale about the past told to us by nerve cells. We are all confident of the veracity of this tale is also a property of our brain, and from it can not escape. But if each of us at least occasionally recalled those 80 milliseconds of deception, the world, I think, would be a little nicer. published