Inside of a Dog: What Dogs See, Smell, and Know

by Alexandra Horowitz

it is very intent on those two things. If we want to understand the life of any animal, we need to know what things are meaningful to it. The first way to discover this is to determine what the animal can perceive: what it can see, hear, smell, or otherwise sense. Only objects that are perceived can have meaning to the animal; the rest are not even noticed, or all look the same.

Thus, these two components—perception and action—largely define and circumscribe the world for every living thing.

What domestic dogs do seem to have inherited from wolves is the sociality of a pack: an interest in being around others. Indeed, dogs are social opportunists. They are attuned to the actions of others, and humans turned out to be very good animals to attune to.

Undesired behavior gets no attention, no food: nothing that the dog wants from you. Good behavior gets it all. That’s an integral part of how a young child learns how to be a person. And that’s how the dog-human gang coheres into a family.

Human noses have about six million of these sensory receptor sites; sheepdog noses, over two hundred million; beagle noses, over three hundred million. Dogs have more genes committed to coding olfactory cells, more cells, and more kinds of cells, able to detect more kinds of smells. The difference in the smell experience is exponential: on detecting certain molecules from that doorknob, not single sites but combinations of sites fire together to send information to the brain.

It is when language stops that we connect most fully.

Dogs are not color-blind, as is popularly believed. But color plays a much less important role for them than it does for humans, and their retinae are why. Humans have three kinds of cones, the photoreceptors responsible for our perception of details and of colors: each fires to red, blue, or green wavelengths. Dogs have only two: one is sensitive to blue and the other to greenish-yellow. And they have fewer of even those two than humans do. So dogs experience a color most strongly when it is in the range of blue or green.

Dogs also have a higher flicker-fusion rate than humans do: seventy or even eighty cycles per second. This provides an indication why dogs have not taken up a particular foible of persons: our constant gawking at the television screen. Like film, the image on your (non-digital) TV is really a sequence of still shots sent quickly enough to fool our eyes into seeing a continuous stream. But it’s not fast enough for dog vision.

Part of normal human development is the refinement of sensory sensitivity: specifically, learning to notice less than we are able to. The world is awash in details of color, form, space, sound, texture, smell, but we can’t function if we perceive everything at once. So our sensory systems, concerned for our survival, organize to heighten attention to those things that are essential to our existence. The rest of the details are trifles to us, smoothed over, or missed altogether.