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Is it true that dogs only see in black and white?

2020-10-25T19:44:46.202Z


Although they do not perceive the same range of colors as humans, dogs' eyes have other advantages, such as the ability to see better in low light. Humans' favorite pet is also capable of perceiving high-pitched sounds from much farther away than we can, and its sense of smell is vastly more powerful.


By Nancy Dreschel - The Conversation

There is no doubt that dogs see the world differently than we do, but it is an urban legend that their eyes are only able to distinguish white, black and slight shades of gray.

While most of us are able to appreciate a full spectrum of colors that goes from red to violet, the eyes of dogs lack some of the light receptors that allow us to distinguish certain colors, especially red and the green.

But they are able to distinguish yellow and blue.

Different wavelengths of light translate into different colors in an animal's visual system.

The top one corresponds to human sight, and the bottom one to that of a dog.

Above: Getty Images.

Bottom: the same image processed by András Péter's Dog Vision Image Processing Tool.

What we see as red or orange

for a dog can be a light brown shade

.

For my dog ​​Sparky, a bright orange ball on green grass could be a light brown ball on an equally brownish grass.

However, its intense blue ball is likely to be appreciated in a similar way.

There is 

an online tool that allows us to check how our dog would see a certain image.

The animals can't speak to explain how they see, but to measure their vision, the researchers had little difficulty training dogs to snout colored discs that lit up.

Later they trained the dogs to play the disc that was a different color from the rest.

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When these well-trained dogs stopped knowing which discs to press, the scientists deduced that at that point they were no longer able to distinguish the differences between colors.

These experiments also showed that 

dogs could only distinguish yellow and blue.

The retinas of human beings, located at the back of our eyeballs, have three different types of cone-shaped cells that are responsible for us being able to distinguish the different colors we see.

But when scientists used a technique called electroretinography to determine how the dogs' eyes reacted to light, they found that the dogs had fewer of these cone receptors.

The light reaches the back of the eyeball, which perceives it thanks to the rods and cones.

These send visual signals to the brain.Getty Images

But it's not just that dogs see fewer colors than we do;

they probably also see less clearly.

Analysis shows that both the structure and the functioning of your eye make objects at a distance appear more blurred.

While for a person a perfect vision has a value of 20/20, the typical vision of dogs is around 20/75.

That means that what a person with normal vision can see clearly from 75 meters, to see it the same, the dog must be at 20. However, since dogs do not read the newspaper,

this lower visual acuity does not affect their life.

There is probably a big difference between breeds when it comes to the visual ability of dogs.

When it comes to hunting, for example, breeders have over the years selected dogs such as English Greyhounds for having better eyesight than other breeds such as bulldogs.

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But the issue gets even more complicated.

While people have a hard time seeing clearly in low light, researchers believe dogs can see just as well during dusk or dawn as they can on a bright morning.

This is because, compared to those of humans, the retinas of dogs have a higher percentage and a greater variety of another type of visual receptor.

These are rods, so named because of their shape, and in low light they work better than cone cells.

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On the other hand,

dogs have a layer of reflective fabric on the back of their eyes that helps them see better in low light.

It is the tapetum lucidum, which works like a mirror and collects and concentrates the available light to help them see when it is dark.

It is this tapetum lucidum that makes dogs and other mammals have that light reflection in their eyes when at night we point a flashlight at their faces or try to take a photo with a flash.

Dogs have the same type of vision as many other animals, including cats and foxes.

The researchers believe that it is important for this type of predator to detect the movements of their prey at night, and for this reason their vision evolved in this way.

Like many other mammals, dogs developed the ability to forage and hunt during twilight or in low light conditions, which was detrimental to their ability to distinguish a greater variety of colors.

This is something that most birds, reptiles, and primates can do.

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Human beings, on the other hand, do not evolve to be active at night, so we retain our ability to distinguish many colors as well as our clear vision.

Before we feel sorry for dogs because they are not able to distinguish all the colors of the rainbow, let's think that some of their other senses are much more developed than ours.

They are able to perceive high-pitched sounds from much further away than we can, and their smell is much more powerful.

Although Sparky may not be able to easily distinguish an orange toy on the lawn, he can certainly smell it and easily find it whenever he wants.

Nancy Deschel is Associate Professor of Small Animal Science at Penn State University.

This article was originally published on The Conversation.

Read the original text here. 

Source: telemundo

All news articles on 2020-10-25

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