When it comes to canine senses, most of the attention goes to the nose.
Dogs' incredible ability to detect the most minute amount of odour is absolutely incomprehensible to us humans. A dog can detect a teaspoon of sugar diluted in a million gallons of water - that is the size of two Olympic swimming pools! They are sniffing machines, which is probably why their eyesight gets so little attention and they are mislabeled as either colour-blind or only able to see in black and white. Well, both labels are dead wrong. Dogs do see in colour, but their vision is different than ours.
An eye is able to detect colour due to the number of cones. Cones are the photoreceptors responsible for the perception of details and colour. Humans have three kinds of cones which are sensitive to red, blue or green wavelengths. Dogs have only two kinds, which are sensitive to the colours blue and greenish-yellow. This means that dogs see a colour most vividly when it is in the range of blue or green.
To get a better understanding of this and how this relates to human vision, anything that we perceive as yellow, red or orange doesn't look the same to dogs. Those colours are more pastel, less vivid than they are to us. The red is not viewed as another colour - as is the case with colour blindness - but rather as a weird pastel shade of red.
The reason dogs perceive colour as they do has to do with their wolf cousins and their ancestors. Being carnivores, they did not need to perceive bright colours like herbivores or omnivores need to. Animals, including humans, that ate a plantbased diet needed to be able to find food and most plants are brightly coloured. Hence our ability to detect bright colours and shapes. Dogs or wolves ate meat. Most of their prey had a coat that offered natural camouflage, or blended into their environment easily. So it was redundant for a wolf to be able to see the bright red of a pepper when it ate the meat of an earthcoloured deer.
What was important was for them to be able to see the camouflaged deer moving. The ability to detect movement is due to photoreceptors called rods. This is where dogs excel in eyesight over humans. Dogs have as many as three times more rods than humans, some breeds even more. In humans these rods are clustered in our peripheral vision, giving us the ability to detect movement best from the corners of our eyes. Dogs' rods are much more dense than those of humans, which gives them the ability to see a fly whizzing by and snap at it with astounding acuity.
But what is even more amazing is what is called "flicker-fusion" rate. This is the number of snapshots the eye takes of the world per second. We assume we see the world as a seamless stream of information, but what is actually happening is our eyes are taking a series of still pictures - 60 per second - of our surroundings, creating a moving picture within our heads. Dogs have a higher flicker-fusion rate. Their eyes take 70 or 80 snapshots per second. They literally see the world faster than we do!
This is also the reason why most dogs pay no interest in (non-digital) TV. TV shows are really a sequence of still pictures sent rapidly to trick our eyes into seeing a continuous stream of information. But that's not fast enough for dogs. When they watch non-digital TV, they see the individual image as well as the black gaps between each image as it passes across the screen at 60 images per second. This slow-moving picture show, plus a lack of scent from the image, makes it uninteresting to most dogs. Digital TV eliminates the flicker-fusion problem and dogs may start watching TV with you. If they could talk they might have an opinion on the Luongo trade too!
But where this fast flicker rate shines is when a dog is trying to catch something we have thrown. They see the tennis ball at its new location a fraction of a second before we do. Wrap your head around that one! Dogs may "see" the world through their nose, but their eyesight is just as amazing. Dogs are so cool!
Joan Klucha has been working with dogs for more than 15 years in obedience, tracking and behavioural rehabilitation. Contact her through her website k9kinship.com.
