It is not a linear process, such as the one that produces images in a photograph or on a television screen.
For our brain, perception is a cycle.
If our perception were linear, energy in the form of light or sound waves would reach the senses, these messages from the outside world would be translated into the language of nerve signals, and the brain would interpret them as objects occupying a certain position in space.
It was this approach that made modeling perception on first-generation computers such a challenge. The predictive brain does the opposite. Our perception actually starts from the inside - from an a priori belief, which is a model of the world where objects occupy a certain position in space.
Using this model, our brains can predict what signals should go to our eyes and ears. These predictions are compared with real signals, and, of course, errors are detected. But our brain only welcomes them. These mistakes teach him how to perceive.
The presence of such errors tells him that his model of the world around him is not good enough. The nature of the mistakes tells him how to make a model that is better than the old one. As a result, the cycle repeats over and over again, until the errors are negligible.
This is usually done with just a few such cycles, which can take the brain as little as 100 milliseconds. A system that builds models of the surrounding world in this way seeks to use all available information to improve its models. There is no preference for sight, hearing, or touch, since all of them can be informative.
In addition, this system seeks to make predictions about how signals from all senses will change as a result of our interaction with the world around us. Therefore, when we see a glass of wine, our brain is already making predictions about what sensations will arise when we take it in our hand, and what taste this wine will have. …
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Where does our brain get the a priori knowledge necessary for perception?
In part, this is innate knowledge recorded in our brains over millions of years of evolution. For example, in many monkey species, the color sensitivity of retinal neurons is ideal for looking out for fruits that are found in their habitat. Evolution built into their brains an a priori hypothesis about the color of a ripe fruit.
In our brain, the visual perception system is formed during the first few months of life under the influence of visual sensations. Some information about the surrounding world changes very weakly and, in this regard, become strong a priori hypotheses.
We can see this or that object only when its surface reflects the light that falls into our eyes. The light creates shadows that allow us to judge the shape of the object. For many millions of years, there was only one main source of light on our planet - the Sun. And sunlight always falls from above.
This means that concave objects will be darker at the top and lighter at the bottom, while convex objects will be lighter at the top and darker at the bottom. This simple rule is hardcoded into our brains. With its help, the brain decides whether this or that object is convex or concave.
Chris Frith, Brain and Soul