Are animals color blind? People's vision may be richer than yours

2023-03-08 Encyclopedias 237+ Ten thousand reading contribute:Blooming
Best analysisAre animals color blind? People's vision may be richer than yours



Should I buy the same toy ball in red or green? What if my cat and dog don't like this color when I buy it back? It is believed that most "excrement removal officials" have struggled with this problem.kSbknowledgebles

But I may want to tell you that your "master" will not mind whether the toy ball is red or green, because in their eyes, there is no difference between the two colors.kSbknowledgebles

01 Are cats and dogs "color blind"?kSbknowledgebles

Isn't it said that cats and dogs have great vision? Why can they not distinguish red from green? In fact, what we want to talk about here is not vision, but a branch of vision - the ability to perceive color. This ability is called "color vision", or "color perception" or "color discrimination". It is our ability tolightThe ability to perceive.kSbknowledgebles

After passing through the prism, white light will be divided into a color spectrum, and the light of different wavelengths will be arranged in order. The wavelength from long to short is red, orange, yellow, green, blue, blue, and purple. Of course, it is not a simple seven colors, but there is a smooth transition between these colors. We can see more than seven colors.kSbknowledgebles


The reason why we can recognize this color difference is because of the cone cells in our eyes. They are responsible for transforming the colors we see into nerve impulses and transmitting them tobrain。 There are three different types of cone cells in our retina. They have different sensitivity to light of different wavelengths. TraditionallyscienceAccording to the order of their wavelength sensitivity peaks, scientists will record them as short (S -), medium (M -) and long (L -) type. Generally speaking, they are called receptors of blue light, green light and red light. It is these three receptors that antagonize and cooperate with each other that we can see the colorful world.kSbknowledgebles

However, compared with humans, both cats and dogs lack one type of cone cells, only the long and short types, which are sensitive to blue-purple light and yellow-green light respectively. This situation is very similar to that of people suffering from red-green color blindness - they lack one of the medium or long cone cells, so they cannot distinguish red from green. Of course, we can't know for sure whether the color vision of cats and dogs will be consistent with that of real human color blindnessrainbowIs it just a simple transition between yellow and blue, but at least whether the toy ball is red or green should be indistinguishable.kSbknowledgebles


In addition to color blindness, cats and dogs are also "color weak" patients. The density of color cone cells in their retinas is much lower than that in humans. In the macula, the most sensitive area of the retina to color, the density of color cone cells in dogs is only about one tenth of that in humans.kSbknowledgebles

However, we cannot say that the world in the eyes of cats and dogs is gray. On the contrary, their vision can be very bright, even in a dark environment. Compared with cone cells, there is also an optical receptor on our retina, called rod cells. Although rod cells have no ability to recognize color, they are more sensitive to light. We can see things at night thanks to them. There are many more rod cells in the retina of cats and dogs than in humans, which is why they can still skillfully run cool in the dark room after turning off the light.kSbknowledgebles

02 FrombirdClass "dimension reduction strike"kSbknowledgebles

When we sympathize with cats and dogs that the world is not colorful enough, the sparrows at the window also sympathize with us.kSbknowledgebles

If we humans are "three color vision", then most birds are "four color vision". Compared with humans, birds have red, green and blue color receptors, as well as a type of cone cells that respond to shorter wavelengths. In most birds, their response peaks even fall into the range of ultraviolet radiation.kSbknowledgebles


The existence of new cone cells adds a dimension to birds' perception of color. If the mixing of red, yellow and blue can be performed on a plane, the mixing of four colors can only be performed in three-dimensional space. The gray objects in our eyes may be dazzling in the eyes of birds, just like the yellow things in the eyes of dogs. We look like red and green.kSbknowledgebles

In addition, there is an advanced structure in the cone cells of birds, which is our lactationanimalNot in. Before the real color receptors in the bird cone cells, there is a small oil drop. This oil drop may be dyed yellow to red by high concentration of carotenoids, which acts as a filter and makes the color recognition of the cone cells more accurate and specific. In the cone cells of birds, scientists have found a total of six small droplets of different colors, including one that is nearly colorless and transparent.kSbknowledgebles

In different birds, the types of oil droplets in cone cells are significantly different. Moreover, species that are far away from each other may have a more similar distribution of oil droplets - if they are in a more similar niche. Maybe this is because, innaturalUnder the selected pressure, the change of oil droplets can be faster than the change of cone cells.kSbknowledgebles

Of course, there are exceptions in birds. The number of cone cells in the owl's retina is very small, and most of them are rod cells that sense dark light. Therefore, the owl's vision is likely to be nearly monochromatic, which is the same as that of cats.kSbknowledgebles

03 Colorful night of geckolifekSbknowledgebles

Between high resolution and color, many nocturnal animals, including cats and owls, choose the former. But the gecko said, "I want all."kSbknowledgebles

Tarentola chazaliae, a nocturnal gecko, has 350 times the ability to recognize color in the dim moonlight than people under the same conditions. In their retinas, there is not even a rod cell sensitive to dark light. There are three kinds of cone cells that are sensitive to light of different wavelengths (although they are all three kinds, they are not red, green and blue in humans, but green, blue and ultraviolet).kSbknowledgebles


The excellent optical properties of gecko eyes enable them to feel the colorful world at night, and the cone cells of their fundus are also large and dense. Scientists speculate that it may be one of the diurnal lizards that has found a suitable nocturnal niche for them. In order to adapt to the new environment, they have to reconstruct the vision system with congenital defects, and use better optical system and more powerful cone cells to overcome the problems caused by the loss of rod cells. The final effect looks good.kSbknowledgebles

04 The hardware is not enough, and the algorithm can make upkSbknowledgebles

Squid, sealfishThe eyes of these cephalopods and our eyes seem to be similar in structure, but in fact they have evolved independently - the eyes are performing chemistryhistoryIt has appeared many times, after all, it is too easy to use.kSbknowledgebles

To some extent, squid's eyes are more "reasonable" than those of vertebrates. The visual nerve fibers of vertebrates are located in the front of the retina. These nerves gather into bundles and leave a "blind spot" on the retina that cannot be sensitized when passing through the retina to the optic nerve; The visual nerve fibers of squid and octopus are located at the back of the retina, and directly and seamlessly converge into the optic nerve, which does not affect the imaging at all.kSbknowledgebles


In the intraocular structure of vertebrates (left) and octopus (right), we can see that the optic nerve fibers of octopus are located at the back of retina. In the picture, 1 is the retina, 2 is the optic nerve fiber, 3 is the optic nerve, and 4 is the visual blind area of vertebrateskSbknowledgebles

But their eyes are not without problems. There is only one kind of optical sensor in the cephalopod's eyes, that is to say, they can only see black and white and gray. They are not as alive as dogs. However, if you have a little understanding of the color changing habits of squid, you can hardly help wondering: it can't see the color. How does it change its color to be the same as the environment, and why should it boast its color in front of the same color-blind opposite sex - it will be easier to see it if it is the natural enemy of fish?kSbknowledgebles

In the face of such contradictions, scientists pointed out that squid octopuses may also have color vision, and the secret lies in their odd-shaped pupils.kSbknowledgebles

Most of the pupils of vertebrates are round, which makes it convenient for light to focus on one point and obtain clearer images. The squid's pupils are completely in the opposite direction, with U-shaped and W-shaped pupils. Such pupils are difficult to form a simple and clear effect on the retina, but will form a colorful halo at the edge of the image due to the inconsistent wavelength of light.kSbknowledgebles


As long as there is enough "calculation power", these halo patterns can accurately restore the color of the object itself, which also has certain requirements for the color itself. If it is a single color, or two colors with similar brightness, they are difficult to form a clear halo, which is why some studies report that squid has no color vision; What squid is good at recognizing is actually the color at the junction of light and dark, which is the same scene when our camera encounters the purple edge problem.kSbknowledgebles

05 The most complex color vision iskSbknowledgebles

Mantis shrimp, or mantis shrimp (members of the Stomatopoda order), may be the most complex group of animals on the earth with color vision, because they have as many as 12 to 16 different optical receptors. We can't imagine the bursting effect of the rainbow in their eyes, let alone the mixing of visible light and ultraviolet light in more than ten dimensions, they can even perceive circularly polarized light - they are still the only group with this special ability.kSbknowledgebles


Such complex color vision, on the one hand, can save valuable computational power for their small brains, on the other hand, it also provides them with more rich ways of secret communication. The door of every hole where there are shrimp crickets may be marked with a big "No one bothers you", but their natural enemies, prey and us can't see it.kSbknowledgebles

Each animal has its own natural way of perceiving the world. Forcibly applying our vision is a huge burden for us to them. So for red ball and green ball, you might as well buy a color you like, and don't stand too far from each other's perspective; Or, buy them all back and see which one the owner prefers?kSbknowledgebles

I recommend you read more about“Color blindness vision ”Cold knowledge ofkSbknowledgebles


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