Compared to humans, dogs see around five times brighter at night, see their surroundings better, see fast objects more clearly and perceive significantly more relevant objects. On the other hand, they see four times worse in the distance and can only distinguish between the colors blue, yellow and gray.
If dogs are in a completely darkened room at night, without any rays of light, they won't see anything either. But your sense of direction is significantly better.
In dogs, the nose is the primary sensory organ. In humans it is the eyes. Depending on their breed, they smell on average between 10,000-100,000 times better than humans.
The reason for this is, among other things, the numerous olfactory receptors in their nose. While people “only” have around 5 million of them, dogs have up to 300 million. [1]
But their hearing also helps them enormously with orientation. Compared to humans, they can hear 4 times further into the distance and can perceive sounds that are more than 3 times higher. [2]
So much for the short answer. Then let's go through the topic in depth.
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#1 Dogs see around 5 times brighter at night
The reason for this is evolutionary. Because dogs originally descended from wolves. These nocturnal hunters are mostly active at dawn and dusk.
There are also other predators such as bears that are also hunting at this time of day. Nocturnal activity also serves as protection.
There are anatomical reasons why dogs see brighter at night than humans. The 3 main differences to us are:
- 1) Dogs have more cones
The light-sensitive cells in the eye are also called “cones”. Dogs have significantly more of it than humans, which means they can absorb more light rays.
The picture above shows what the same environment looks like for us humans and for dogs. And as you can see, dogs see as clearly at night as we would at dusk.
- 2) Dogs have larger pupils
The pupil size varies depending on how light or dark it is. In humans, the pupils are on average around 3 mm in size in daylight and around 7 mm at night. [3]
The pupil of dogs, on the other hand, is many times larger depending on the breed. The lens itself, which is located behind the pupil, is around 300-400% larger. [4]
Or to put it another way: In dogs, the eyes can absorb between 3 and 4 times more sun rays simply because of their larger pupils.
- 3) Dogs have reflective retinas
Have you ever wondered why dogs' eyes glow at night when you shine a flashlight on them?
The reason for this is a reflective layer behind the dog's retina (“tapetum lucidum”). This layer reflects the incoming light back through the lens.
The eye therefore has two chances to absorb light rays. By the way, humans don't have this layer. That's why our eyes don't glow in the dark. [5]
The effect? To dogs, dusk almost looks like bright sunshine. Even catching the Frisbee in these lighting conditions is no problem for them.
However, if it is completely dark – i.e. without any sunlight – then dogs only see black. Just like you would only see black with a night vision device.
Because night vision devices, like dogs' eyes, only amplify the existing light. If there is none of this, then the effect will not occur.
Dogs have larger pupils, more cones and a reflective layer in the retina. This means you can see around 5 times brighter than humans at night. However, dogs are also blind in a completely light-tight room.
#2 Dogs only see yellow, blue and gray at night
Dogs don't see the world in black and white. That's a myth. Instead, they have 2 color receptors in their eyes that help them see all shades of blue and yellow. [6]
Or as ophthalmologists would say: dogs are “dichromats”. They can therefore only distinguish around 10,000 different colors from one another. Gray tones are also included.
Have you ever wondered why the obstacles in dog competitions are always blue and yellow? Well, now you know about it.
Our world, on the other hand, is much more colorful. Because we are so-called “trichromats”. Specifically, this means: Instead of only seeing yellow and blue tones, we can also perceive red. [7]
Because of all the color combinations, we can distinguish around a million colors from each other. Or to put it another way: dogs only see around 1% of the colors we do.
This applies both during the day and at night.
Now you know why I constantly have to touch my head when it comes to red dog toys. Because dogs simply cannot see this color.
Image may be used under these guidelines.
Ready for a crazy mind game? Butterflies don't just have 3 color receptors, but 6. Imagine how colorful the world looks with them.
Hold onto. There is more. The mantis shrimp even has a whopping 16 color receptors. So more than 5 times more than us humans.
Compared to humans, dogs only see the world in yellow, blue and gray at night. They cannot perceive red tones due to the lack of a color receptor. This means you can only distinguish a total of 10,000 colors from one another.
#3 Dogs see fast objects more clearly at night
How many images our eyes can see per second depends on our attention and the lighting conditions. The values fluctuate between 10-60 light stimuli per second.
This means that in the best light and maximum attention we have a “flicker fusion frequency” of 60 Hz. [8]
Now you also know why televisions from the 90s often flicker. Because the refresh rate here is usually below 60 Hz.
Specifically, this means: We can perceive the short pauses between the images. On the other hand, we can only see very fast objects, such as a racing motorcycle, in a blur.
In dogs, the maximum flicker fusion frequency is a whopping 80 Hz. So on average they see around 33% more images per second.
Specifically, this means that dogs see fast things that we only perceive as blurry, even at night. [9]
Image may be used under these guidelines.
Catching balls, Frisbees and other fast objects is therefore much easier for dogs. Your visual reflexes are simply 1.3 times better.
Now you know why you can rarely kill household flies. Because they perceive up to 250 images per second. So you see our hand so clearly, as if in slow motion.
Dogs see up to 1.3 times more images per second during the day and at night. They can therefore see even fast objects, such as a wild animal in full sprint, clearly at all times. The human eye, on the other hand, can only perceive such things in a blur.
#4 Dogs have a harder time seeing into the distance at night
Dogs' eyes are not better than humans at everything. When it comes to seeing into the distance, for example, we are clearly superior.
An average human has 20/20 depth perception. So it sees things completely clearly even from a distance of 20 feet (around 6 meters). [10]
In dogs, depth perception is only 20/80. So you see things 20 feet (6 meters) as clearly as we see things 80 feet (24 meters) away.
Specifically, this means that people see into the distance around four times better than dogs. [11]
Image may be used under these guidelines.
But why can dogs see a cat walking across the meadow 50 meters away at night? There are 3 reasons for this:
- Dogs' primary sensory perception is their sense of smell, which allows them to smell objects that are far away.
- Dogs not only hear further into the distance, but also significantly more sounds that are simply inaudible to us.
- Dogs' perception is much more focused (see #5).
The natural shortsightedness of dogs therefore has significantly less impact in practice than poor eyesight in humans.
Compared to humans, dogs see around four times worse at night. Everything from a distance of around 6 meters becomes increasingly blurry to them. With the help of their excellent sense of smell and hearing, they can still perceive almost all relevant objects from a distance.
#5 Dogs perceive fewer objects at night
Have you ever bought new shoes and then suddenly saw that so many people were wearing the same model? This is the work of your selective perception.
Because without filtering the millions of sensory stimuli per second, you would be constantly overwhelmed with unimportant things. By the way, dogs have the same ability.
Compared to humans, however, dogs' filters are much finer. Therefore, even at night, they almost exclusively perceive objects that are relevant to them and hardly anything else.
This is also the reason why dogs have much more trouble recognizing instinctively “unimportant things” as important.
Because if a guide dog doesn't consider a curb or zebra crossing important, then it can be fatal for both him and his owner.
The selective perception of vision is significantly more focused in dogs than in humans. You therefore only see absolutely relevant objects both during the day and at night. They ruthlessly ignore everything else.
#6 Dogs see their surroundings better at night
You've probably noticed that even when you focus your eyes on your nose, you see moving objects around you.
This is so-called “peripheral vision”. This type of indirect vision is significantly better in dogs for anatomical reasons. The reasons for this are twofold:
- 1) Increased eye relief
On average, an adult measures 6.2 cm between the pupils – the so-called “eye distance”. Depending on genetics, this distance varies between 5.4 and 7.2 cm. [12]
For dogs, the distance between their eyes depends primarily on their breed. The average eye relief here is around 7.7 cm.
Image may be used under these guidelines.
Or to put it another way: Dogs' eyes are around 24% further apart than people's. Your perspective is therefore broadened.
- 2) Side eye position
While people's eyes look straight ahead, dogs' eyes are oriented slightly to the side. And that has advantages as well as disadvantages.
The advantage of this is that dogs can perceive their environment much better at night. On the other hand, they see things that are in front of them somewhat worse.
Or to put it in technical terms: dogs' peripheral vision (side) is better, but humans' foveal vision (frontal) is superior.
Now you also know why you should never throw treats from the front, but rather slightly to the side. Otherwise…