Gazette Vet: How Dogs Perceive the World
By John Andersen, DVM
Helen Keller, both deaf and blind since a toddler, went on to become a world famous speaker and author, advocating for people with disabilities and for a number of political causes. Even though she lacked the two most important and most refined of the human senses, she was able to use her mind and intellect to accomplish these goals. Conversely, the story of a wolf in the wild who was both deaf and blind would have had a much quicker and tragic end.
We sometimes forget the major differences in the way we perceive our world and the way our dogs perceive it. As humans, although we have very good vision and pretty good hearing, it is mostly our intellect which drives our survival and innovation.
Now don’t be offended when I tell you your dog isn’t capable of higher thinking, but it’s true—he is but a simple-minded creature. Instead of relying on reason, logic, and forward thinking, his survival is directly linked to his senses and his instinct. His mind is not made for deep thought or contemplation, but rather simply to process his immediate surroundings and react. Take away his vision and his hearing and you have effectively taken away two- thirds of his intelligence.
But that is not to say your dog is not smart. I find their sensory perception and their trust of their own natural animal instinct to be pretty incredible.
We simply cannot fathom how incredible the dog’s sense of smell is. A dog’s sense of smell is thought to be 1,000 times more sensitive than ours. Whereas we have about 5 million olfactory sensors in our nose, dogs have 100-300 million, depending on the breed! Also, although the dog brain tends to be about one-tenth the size of ours, the region of their brain that processes smell is 40 times greater than ours.
Consider the working dogs who can sniff out narcotics or explosives, or find survivors in the wreckage of some disaster. There are even dogs who have been trained to detect certain types of cancer by smell.
Often while I’m walking my dogs around the block, there are a few choice spots they simply must stop and sniff. I feel like if I didn’t eventually pull them away, they could spend hours sniffing one spot. Where we humans see just a clump of our neighbor’s decorative grass, our dogs can smell an entire story. They can smell the urine of other dogs and are likely able to detect if they were male or female, strong or weak. They can probably smell and remember how those dogs’ urine has been changing, how often they come to this same grass, how their health is changing, perhaps what they’ve been eating. And it’s probably a no-brainer to them that some mice live beneath that grass, and bugs, and dirt… I can only imagine what my dogs think of me when I come home from work. I let them smell my pants and my shoes, telling the story of the pets I saw that day and much, much more.
Dogs’ hearing is also better than ours, though less dramatic than our smell differences. The human hearing range is from about 20 Hz (low) to 20,000Hz (high), while a dog has a similar low end, but can hear frequencies up to 45,000Hz. Hence the dog whistles. Or why they may bark at the vacuum (it probably has a lot more sounds than we hear). Additionally, if you’ve ever had a dog with thunderstorm anxiety, you know that they can tell a storm is coming well before we can. Whether they actually have better low-end hearing or have the additional ability of sensing pressure changes better than we do is unclear. Testing a dog’s hearing has proven to be very difficult, since they don’t give us any feedback, but I think there is more to this sense than we yet know.
Although many aspects of human vision are superior to dogs’, they still hold some advantages. Our distance vision is generally better (we are at 20/20 while they are roughly 20/75) and our near vision is better as well. However, dogs have much better peripheral vision than we do since their eyes are located more on the sides of their faces. They also have much better night vision than we do—due to having both more low-light cells in their eyes and a reflective layer in their retina that gives them that eye shine at night. Although dogs are not truly color- blind, they tend to see colors more in shades of blue and yellow, with little ability to pick up greens and reds. Dogs can see images on the TV, but many also see a lot of flickering light as their flickering light resolution frequency is different from ours. One of our dogs never pays any attention to the TV, while the other goes crazy anytime there are other dogs on.
When we compare the senses and intelligence of dogs and humans, it is easy to consider where one species is better or worse off than another. But I think it more appropriate to just marvel at the creation of the dog. A perfect blend of vision, hearing, and smell matched with a brain that is uniquely connected to react to these senses and lead to incredible instinctual behaviors. This has allowed wild dogs like wolves, foxes, and coyotes to survive for ages in the ruthless natural world. And now we have domesticated dogs with wonderful personality traits and characteristics, but still with these incredible senses and instincts.
So the next time you take your little wolf on a walk, let them indulge a little when they get to their sniffing spots. There’s more than meets the eye!