Eyes are one of our senses which we use to accept information from surroundings. An eye is like a camera lens. A retina is similar to a negative film or an image sensor in a camera. They both record visual pictures (information). Nerves and neuron paths including parts of a brain for interpreting and processing the visual pictures are the same as camera electronics and an SD card of the camera.
From eyes to brain
Eyes record pictures on the retina through a lens. There are photoreceptors placed on the retina. The receptors accept photons (a unit of light). The retina works the same way as the image sensor in the camera. Each receptor converts light to electric impulses. The impulses activate neural paths and neurons between the eyes and the brain centre for processing and interpreting the visual pictures.
Interesting facts about processing visual information and perception
Threshold sensitivity
Each of our senses (sight, hearing, smell, …) has a property called threshold sensitivity. It is the minimal amount of an input information (strength of light, strength of taste) to be able to intercept and process. How far can we see?
It was researched that the human eye is very sensitive. It’s as sensitive as physical laws allow it. You can see a lit candle from a distance of 48 km. If we take it from the physical point of view, each photoreceptor can sense only 1 photon. It means that the photoreceptor sends an electric signal to the brain for processing when one photoreceptor on the retina is hit by only 1 photon.
It is interesting that it was tested with a flash of light with the strength of 100 photons. Only 7 of them reached the retina, 93 disappeared. Let’s say it’s attenuation somehow.
Physical intensity and psychological intensity
One would say that when the intensity of a stimulus grows (pain, noise), it must grow the same way (linear growth) when it comes to our psychological perception. It’s not true. It differs for each sense and a stimulus based on the Steven’s power law.
Let’s use an analogy as an example: Imagine a flash of light enters your eyes. The amount of the light is 1000 photons. The next flash is 2000 photos. Will you psychologically perceive the second flash as 100 % stronger than the first one? No, you won’t.
Ψ = Φr is an equation for the phenomenon. The exponent r differs for each sense and stimulus.
The psychological perception of a physical stimulus doesn’t grow linear but exponentially.
Electric shock has r = 3,5. It means that whenever the amount of the shock rises, it is perceived stronger psychologically (exponentially) more. The r for warmth is 0,7. It means than when the warmth grows, you perceive it psychologically as growing less in relation to the real temperature difference on a thermometer.
Thus the phenomenon saves your life when you get an electric shock (more pain). It also means that when you raise the temperature of water in your bathtub or in a sauna, you will feel more pleasantly. You perceive the temperature growing psychologically slower than it actually rises on the thermometer.
That explains why a frog stays in a water which is gradually heated up.
Sensitivity and bias
Have a look at the picture below. The purpose of the picture is to find out a stain. You can see it at the rightmost one. It’s not possible to see it at the leftmost one. If you saw the leftmost one first without being told to look for the stain, you wouldn’t probably find the stain. However if the pictures were presented to you from the rightmost to the leftmost one, you would probably see the stain in the leftmost one.
Why is it like that? Because if you’re told to look for something, your brain wants to find it. Even though there may be nothing, you can still find something there.
There is a specific prejudice towards what we perceive based on what we think. In conclusion, it doesn’t depend only what’s actually in front of your eyes, but also on what you want to see.
In general, it can mean that you can look for something what you were told to for your whole life. Meanwhile you miss something what you would see, if you weren’t influenced by your mind or by bystanding wise guys.
Cone cells and rod cells
The retina is equipped with photoreceptors. There are two types: cone cells and rod cells. They are photodetectors (as photodiodes in a camera). They absorb light and excite electric impulses (voltage). The impulses are then sent to the part of the brain designated to process them.
The cone cells are for high resolution, good colours and for using during a day. On the other hand, the rod cells are adjusted to detect light in the night. The cone cells are like a camera set to ISO 100 – good for photographing during the day. The rod cells are like a camera set to ISO 12800.
It is very easy to switch between the two ISO values in the camera, adjust it to the night and start shooting photos. How long does it take your eyes to adjust?
The cone cells (daytime receptors) are swifter to adapt to the dark. It takes up around 5 minutes. The rod cell (nighttime receptors) are active during low light and the night. They are turned on 10 minutes after entering a space without light. They are fully adjusted after 20–30 minutes. Then you can see details even in the dark.
Size constancy
Take a pencil in your hand and move it front of your eyes and think about its size. Now extend your hand to the maximum distance. Is the pencil bigger or smaller? It seems to be of the same size. Even though, it takes up less space on the retina. How is it possible?
Parts of the brain used for processing and interpreting pictures use something called guidelines (hints). The guidelines help us to see the pencil still of the same size no matter how far it is. The guideline for the size is the distance between your eyes and the object being looked at. The brain can calculate the size of the pen in relation to the distance. If the brain didn’t have the distance information, it wouldn’t probably be able to calculate the correct size of the pencil.
If there was a human whose brain would be damaged in the part which processes the size constancy (calculating the perceived size) and you would ask him if the pencil is smaller (when it’s further), they would probably tell you that the pencil is smaller.
902 instead of 30 720 bytes
When a camera shoots a photo, it saves it in various file formats. The first one is RAW which includes all the information about the scene. It can be as big as 50 to 100 MB. The second one is JPG. The same photo has 8 to 12 MB in it. There is less information in the JPG. However, we perceive the final photo the same way. It’s called compression.
Our brain works the same way. The process is named abstraction. Due to it we can’t recall all details of a human face, yet it’s enough to be able to recollect their mood and a face expression. We save up only the needed visual information and characteristics in order to orientate ourselves among human faces. We spare up memory and processing power this way.
The picture on the right was created with help of basic shapes (lines and ellipses, circles) from the left one. When you look at them, you see a frightened man. The actual face looked more like the left one, but our brain saves up only the crucial visual information as in the right picture. This method of processing input from the surroundings helps us not to be overwhelmed and be able to orientate ourselves in our environment.
Imagine an autistic person who has a problem with processing input information from the surroundings in their senses. Their brain tries to save up all the visual information as RAW. It overwhelms their brain processing centres and there is no capacity left to other activities.
Are we machines or are the machines created based on us?
After reading the article you may be in two minds whether were are spontaneous biological creatures or artificial machines as the ones we’ve invented so far (computers, cameras, optics). Were we created by somebody? The question sounds very intriguing and worth exploring. Nevertheless the reality is simpler. Everything what we’ve created originates from us and is constrained by our own limitations. It means that a camera is just a copy of our own optical eye system. Computers work based on a higher voltage (1) and a lower voltage (0) and that’s the way transistors pass on information. Neurons and nerves work the same way in our brain and the body.
Source:
Nolen-Hoeksema, S., Fredrickson, B., Loftus, G. R., & Lutz, C. (2014). Atkinson & Hilgard’s: Introduction to psychology.
