HOW DOGS SEE?
One of the most common curiosities among dog lovers is the one concerning the way of seeing of our four-legged friends. Often, in fact, one wonders if dogs recognize colors or if, instead, they see in black and white. The answer is actually in an intermediate way: so let's find out how dogs see.
Do dogs see colors?
The old theory that dogs see in black and white has been disproved by several studies. It is true, however, that they do not perceive colors like humans: while humans are sensitive to three main colors (red, blue and green and their combinations), dogs are only sensitive to two, blue and yellow.The dog has two types of cones. A type more sensitive to the wavelength from 429 to 435 nm defined as violet, a second type sensitive to the wavelength of 555 nm, yellow. Dogs appear to have no green-type cones and are therefore unable to distinguish some shades from green to red. Presumably the visible spectrum of the dog varies from purple to blue-violet and yellow.
you should think of a curious thing: the dog does not see red, but most of its toys are of this color: this is because the objects have been designed to hit the owner and not the animal. Furthermore, the dog would also be able to recognize the different shades of blue, yellow and gray.
(The most common refractive error found in dogs is myopia in which a predisposition to the breed is recognized in the German Shepherd and Rottweilers. Myopia is also found in older dogs as it is associated with the loss of elasticity of the lens. Hyperopia and astigmatism are rare in dogs.)
DIFFERENCE BETWEEN DOLYCEPHALIC DOG AND BRACHYCEPHALIC DOG
First of all it is useful to know that the dog's field of vision is very different from ours. From the image you can see a big difference in binocular vision (therefore with both eyes). The monocular visual field (in yellow, with only one eye), seems to be much more developed in the dolichocephalic dog.
Dogs that have this morphology have a longer than a broad head. A typical example of a dolichocephalic dog is a greyhound, but so are most mestizos and many other dogs.
A brachycephalic dog is instead the Boxer for example: the head is more developed in width than in length. The monocular field of view (with only one eye therefore), which in humans is decidedly underdeveloped, would instead allow some dogs to have a vision that can reach up to 270 °.
Do dogs see in the dark?
Yes, dogs are able to see in the dark and at night, so much so that night vision is one of the most important characteristics of these animals: for this reason they are considered skilled night hunters. The dog's pupil can expand considerably, so if there is little light, the retina is stimulated more. On the retina we find reflective cells that form a layer of tissue called tapetum lucidum, characteristic of nocturnal mammals. As proof of this, we humans are not gifted with it.
Clearly, in total darkness, the dog will not be able to see anything because it needs a minimum of light which, even if dim, is sufficient to stimulate the cells of the retina.
The dog’s eyesight: closeness and distance
Dogs are predators, so they don't see very well up close. They need the object to be at least 50 cm away from their eyes.
Man, on the other hand, can even reach 15 cm.
The dog beats humans over long distances and in particular if the object is in motion, this is also the result of the evolution of dogs as predators. So, when you want to call your dog and you are a bit far from him, move a little and it will be easy for him to see you, even if you are far away!
The third eyelid
The eye of the dog, and that of other animals such as the cat, in addition to the upper and lower eyelids is also equipped with a third, the nictitating membrane.
This moves independently and smoothly until it covers the entire eyeball, just like a windshield wiper would do to clean a car windshield.
In a healthy dog, the third eyelid is not visible, but if it is inflamed it can appear red and swollen and is often due to bacterial conjunctives.
Some curiosities about dogs in front of the TV screen.
What goes through the head of your four-legged friends when they stop in front of the TV (or the screen of a tablet or a PC)? What are their favorite subjects and, above all, do they have fun?
More than the image, it is the sound that first captures their attention: the yelps and barks of other dogs, compliments and commands addressed by humans and the squeaks of rubber toys are stimuli that attract these animals to the screen.
However, the methods of use are different from ours. Dogs do not stand still in front of the images but are interactive spectators, who approach the screen to get a better look and frequently commute between the TV and humans sitting on the sofa.
Several studies that have tracked canine eye movement have established that dogs love to observe scenes featuring their fellow humans. Provided they're short films: Unlike humans, dogs have lightning-fast interactions with TV, sometimes less than 3 seconds in length.
Check what dogs see when they watch TV
We do not know if they prefer a certain type of programs, for the type of emotions they arouse. Placed in front of three screens with different contents, the dogs show that they do not know how to choose, and that they prefer only one screen, regardless of the image shown. Remaining on the subject of preferences, these are very linked to the character of the dog, to his experience and to what his master looks at: even in front of the TV, our faithful friends follow human gestures, and put their eyes where we place them.