Are dogs colour-blind?
For decades, it was widely believed that dogs live in a black and white world. This idea was attributed to Will Judy, who, in 1937, declared that dogs had poor vision and were only able to see single shade and general outlines and shapes. Further research in the 1960s affirmed his theory and the idea that dogs are colour-blind became widely accepted.
What is colour-blindness?
People with colour vision deficiency find it difficult to identify and distinguish between certain colours.
It’s sometimes called being “colour blind”, although total colour blindness (an inability to see any colour) is very rare.
There are different types of colour blindness and in extremely rare cases people are unable to see any colour at all, but most colour blind people are unable to fully ‘see’ red, green or blue light.
The most common forms of colour blindness are collectively known as ‘red/green colour blindness’. Although ‘red/green colour blindness’ is a common term, there are different types and severities (Source: Colour Blind Awareness).
Being ‘red/green colour blind’ means people with it can easily confuse any colours which have some red or green as part of the whole colour. So someone with red/green colour blindness is likely to confuse blue and purple because they can’t ‘see’ the red element of the colour purple.
How do dogs’ eyes compare to humans?
There are some basic differences driven by evolution and function. Dogs are nocturnal hunters, tracking and catching their food at night and as such their eyes adapted to see well at night and focus on movements as opposed to a trichromatic vision (full colours). Additionally, there are structural differences as well. The retina has:
- rods, which are responsible for catching movement and working in low lights; and
- cones, which work in bright lights and control colour perception.
Dogs’ eyes have more rods than humans, which means they can see much better at night. Dogs also have a layer of eye tissue that humans lack called the tapetum lucidum, it reflects light into the retina.This boosts dogs’ night vision even more and is the reason why dogs’ eyes shine in the dark.
Can dogs see colours?
Dogs can see colours, but only in shades of blue and yellow. Because dogs can only see these two colours, they have dichromatic vision. They can also see shades of grey. Colours such as red, orange, and green are out of a dog’s colour spectrum, so these colours are not visible to dogs. This is why hunters can wear orange to be visible to other hunters but not to animals. People have what’s called trichromatic vision, which means we can see a lot more colours than dogs.
Dogs can make out yellow and blue, and combinations of those colours. This renders a lot of the world greyish-brown. What does your dog think of your lush green lawn? It probably looks like a field of dead hay. That bright red throw on his sofa? Still comfy, but it probably comes across as a dark brown blob to your dog.
How good is a dog’s eyesight?
A dog’s vision is blurry. If a dog were a human, they would be considered near-sighted and would need glasses to see objects farther away, like the board in the front of the classroom or a road sign. However, dogs’ eyes are spaced slightly farther apart than ours, at a 20-degree angle. This greater angle increases the field of view and therefore a dog’s peripheral (side) vision.
How about sighthounds?
Sighthounds are dogs historically bred for hunting by speed and sight. Their vision extends to a whopping 270-degree field (our range is only 180 degrees), allowing them to effectively scan the horizon for possible prey. Sighthounds also have something called stereoscopic vision, which means they are well-suited to seeing moving objects. Their eye placement and vision not only allow them see objects behind them but also over a half-mile out in front! However, when it comes to the spectrum, theirs is as limited as any other dog breeds’.
What does it all mean to you and your dog?
Now that you know that dogs don’t see certain colours, it would make sense to choose products for them that feature the colours they can see. This knowledge may help explain why some dogs go crazy over yellow tennis balls, but are apathetic about the same ball in pink or red.
When you’re throwing a ball or any fetch toy for your dog to retrieve in the grass or the lake, don’t choose something red, or he’s likely to lose it. And if you’re teaching him to differentiate between two toys, it would be wise to go for one blue and one yellow.
So when your dog runs past the red ball you have just thrown, she may not be stubborn or stupid, it may be your fault for choosing a toy with a colour that is hard to discriminate from the green grass.