Do you perceive what you see? And/or do you see what you believe?
These questions are not as trivial as they may first appear. The answers, however, are no and yes, and now I'll try to tell you why.
However perfect you may think your vision is, your mind is actually playing a trick or two on you.
Once light is transmitted through the cornea it eventually passes the pupil and is refracted through the lens of your eye. This refracted light strikes the retina at the back of your eye, which is packed with sensory cells capable of detecting differences in light intensity and discerning electromagnetic radiation in the red, blue and green part of the visual spectrum. At the center of the retina you find the macula, which is the most sensitive part of your retina, containing the highest density of sensory cells, allowing you to perceive in greater detail what is straight ahead of you compared what is located to your sides.
Now, you may think that "what you see is what you get", or that your eyes are actually telling you what you see. However, in order for you to see anything at all, the sensory cells in your eyes must pass signals to your brain through the optical nerve, located close to (slightly below) the macula, which means that your brain is pretty important to your perceptions. The optical nerve, however, is not covered with sensory cells, which leaves your perception with a blind spot. Considering that there is effectively a black spot in your sensory apparatus, pretty much like a big speck on your camera lens, you would perhaps expect to see a black spot in your vision, but fortunately our brains have figured out a way such that we are relieved of the annoyance of having a permanent speck on our vision. Once the signals from the sensory cells have been transmitted to your brain, it first realizes that the image is clearly upside down and laterally reversed, an artifact caused by the refraction of light through the lens. Since seeing everything upside down would be slightly inconvenient, your brain cleverly swaps the information from the sensory cells such that the information it is passing to your consciousness is once again refracted to reflect what your brain believes is going on outside your eyes in your field of vision.
So far so good. The three tier process of refraction, sensory excitation and nerve signal post processing (mental refraction) serves you pretty well. But what about the black spot? Now, your clever brain uses a trick to solve this problem. In fact, your brain is cheating on you, and making a pretty good case at it too. Since there is really no information available from the black spot, your brain just decides that the information it is missing out on is probably related to the information it received close the black spot, and so it makes up some information about what may be hiding behind the speck in your visual perception, which it passes along to your consciousness together with the information it actually received. Like a child who believes everything a parent says to be true, you typically tend to believe that the information you receive from your visual perception is true (and rather complete), and that it gives you a pretty good idea about whats going on around you?
Now, that is where you are wrong. Apart from the black spot, what your visual perception gives you an idea about is only related to structures reflecting or emitting light in the (humanly) visual part of the electromagnetic spectrum. Considering your immediate surroundings, the volume of what surrounds you is in fact not visible to your human eye, unless you have some superman x-ray vision skills allowing you to see the air itself or particulate matter of a size smaller than the wavelength of violet light (about 420 nm). In order for something to be visible, here meaning detectable, there must be an interaction between that which is to be detected and the medium which transmits the information that something is "there". Electromagnetic radiation in the spectrum of 400-700 nm wave lengths is the medium for human detection by visual perception. Our clever minds have, however, allowed us to understand the limitations of the human perception, and other means of detection has been discovered for us to "see" that which is smaller than visual light.
As an example, electron transmission or diffraction can be used to look at nano-sized particles, and even the atoms themselves can be discerned at special conditions using the particle-wave duality of electrons. Ultraviolet light and X-rays are both used for detecting nano- and sub-nano-sized particles (although for experimental reasons it is difficult to obtain sub-nano-sized/ atomic resolution). Now, at the other end of the electromagnetic spectrum we find length scales that would be useless for detecting such things which you might find useful, like the nearest pizza shop, where you parked your car or the hotel you are staying at. The wavelengths are just so large that such radiation doesn't really interact with most of the things we humans surround ourselves with, which is why they are perfect for transmitting radio or TV signals. Mountains and valleys, however, do pose difficulties even to these signals, which is why we have been clever enough to place tall masts on top of every remotely accessible hill or mountain in order for us to watch our favourite TV shows and discuss them later on the mobile phone. My guess is that you would be quite troubled and dizzy if you were to see all this information being transmitted all around you, not to mention all the tiny particles your human vision (thankfully) overlook. I mean, you don't really want to "see" what your neighbour is discussing on the cellphone, do you?
Oh... really? Well, the thought did cross my mind. Anyway, given this knowledge about visual perception, and the fact that this is rather common knowledge in our modern world, people still tend to believe (for the most part) in only what they can see, meaning what they can see with the unaided eye. So, although the world isn't really "what you see is what you get", people tend to ignore this fact and choose to believe it is. You may say that there is no big harm done in doing that, but as I'm going to explain to you, the limited sensory perception of the human eye isn't the only thing limiting what you see, in fact your brain has another trick up it's sleeve, which allows it to simplify the information which it passes into your consciousness by several orders of magnitude.
So what is the big trick the master magician (your brian) is pulling on you? It's the game known as "naming it". Once you start learning to express yourself with sounds and words, your brain develops an enormous aptitude for naming things, and the more you know about certain things the more spesific names you will find yourself using for its components. Naming things does have the advantage that you will be able to recognize certain things that you have seen before, in example: this is my mother, this is my father, this is my foot and these are my toes (did anyone say smile?). Recognizing certain aspects of your surroundings is undoubtedly utterly important and has implications that I'm not going to discuss now, but once you start to recognize things you also start paying less attention to the details of that which you have put a name tag on. This is best seen when people are asked to try to describe or draw something they have seen, like a holiday memory they are telling their friends about. Most likely you are going to find that most of the time you spent on holiday you didn't really use the visual information that was available, but short-circuted the whole perception process by saying "hey, I've seen that before", the beaches were, well sandy, and the sky was blue... ok, so much for the details, thank you.
Now, the reason why some people appear to have exceptional skills at drawing isn't because they are so much better at moving the pencil, but because they do not short-circuit the perception process. Instead of saying that he sees a man, short curly black hair, wearing jeans and a T-shirt, the skilled drawer only sees lines and curves, intersecting angles and angles relative to an imaginary horizontal and vertical axis and shades of light and darkness. Seeing these details while avoiding to name them allows for the continuation of actual perception. Once you start naming things, your mind begins to play the game of recognition, and you start leaving out the details. This is why people have experiences that they find to be eye-opening, or that something happens which allows them to see things in a new perspective. All this means is just that they found their naming tags to be inadequate, and therefore had to throw away a whole bunch of them and replace them with some new and more refined tags, which allowed them to truly perceive (no short-circuiting) their surroundings for a short while in order to come up with some new tags.
So much for the human visual perception huh? I believe I've now briefly answered the question of whether you perceive what you see, and/or see what you believe. As I've already said, the answer is no and yes, which should be evident by now. Your visual perception is limited by two tricks, the "filling in trick" and the "naming trick", which allows your brain to send you low resolution information about what's going on around you, unless you start complaining to it about the poor quality imaging. The "filling in trick" is where your brain lets you see what it believes it is missing out on because of the black spot, while the "naming trick" is affecting both issues by reducing your visual perception to lumps of information that you have already tagged with certain names, allowing you to see what you believe you have recognized, and consequently not see what is visually perceptible.
