The recognition of visual stimuli in mammals is the result of the joint work of the eyes and the brain. At the same time, a significant part of the visual information is processed already at the receptor level, which allows to significantly reduce the amount of such information received by the brain. Elimination of redundancy in the amount of information is inevitable: if the amount of information delivered to the receptors of the visual system is measured in millions of bits per second (in humans - about 1 bits/s), the capabilities of the nervous system to process it are limited to tens of bits per second.
The organs of vision in mammals are, as a rule, well developed, although in their life they are of less importance than for birds: usually mammals pay little attention to immovable objects, so even cautious animals such as a fox or a hare may come close to a human who stands still without movement. The size of the eyes in mammals is relatively small; in humans, eye weight is 1% of the mass of the head, while in a starling it reaches 15%. Nocturnality animals (for example, Tarsier) and animals that live in open landscapes have larger eyes. The vision of forest animals is not so sharp, and in burrowing underground species (moles, Gopher, Zokor), eyes are reduced to a greater extent, in some cases (marsupial moles, mole rats, blind mole), they are even covered by a skin membrane.
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