But first, let's see what our world is like in the eyes of dogs.
There are two kinds of cone cells in the retina of dogs, which can recognize short-wavelength and medium-long wavelength light waves, that is, they can feel blue light (short-wavelength light waves) and red and yellow light (medium-long wavelength light waves). Due to the lack of cone cells, the color of the world in dogs' eyes is very monotonous, unlike the colorful world in human eyes. However, human beings have three types of cone cells, which enable us to see all colors of light in the visible spectrum. Because dogs only have two kinds of cone cells, the colors that dogs can distinguish are the same as those that red-green color blindness patients can distinguish. However, color-blind people can see many other different colors, so can dogs see these colors, too? Scientists have adopted two methods to determine this.
One way is to illuminate the dog's eyes with a beam of colored light, so that an image reflected from the dog's eyes will be obtained, and scientists will study this reflected image; Then compare it with the image of the same light reflected in someone's eyes.
Another way is to train dogs to "tell" scientists what they see. In the experiment, scientists showed dogs several groups of colors in succession, each group had three colors, and two of them were the same. In addition, with a little training, dogs will point out the unique colors of each group to scientists with their noses. Scientists only need to constantly change the color of light and repeat this process, and they can come to the conclusion that the world in the eyes of dogs is black. White and dark gray, mixed with red and yellow light of medium and long light waves and blue light of short light waves at the same time, the world is just like the picture in black and white TV, but the brightness of black mortar is different, but the color change is indistinguishable. Guide dogs can distinguish between red and green signal lights because the brightness of these two lights is different. The dog's discrimination of gray shadows is very subtle. With this ability, it can distinguish the changes of light and shade on objects and produce stereoscopic visual images.
Dogs are poor, even if their owners are far away, especially when the smell outside is not very strong. Even if you stand next to it, it may not know. It judges its owner by its voice. When my dog is playing outside, I often try, but every time I fail. It is really invisible.