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

by Alexandra Horowitz

Bringing the dog to the scene of the crime to enact the punishment is common—and is an especially misguided tactic.

Instead of a punishment happening to them, they’ll learn best if you let them discover for themselves which behaviors are rewarded and which lead to naught.

Undesired behavior gets no attention, no food: nothing that the dog wants from you. Good behavior gets it

is only off the trail to you; to the dog it is a natural continuation of walking, and he will learn about trails in time. You may never see the invisible thing in the bush, but you learn, after a dozen walks, that invisible things are in bushes, and the dog will return to you.

There are bites done out of fear, out of frustration, out of pain, and out of anxiety.

wolves. Stray dogs—

do not take on more wolflike qualities.

Neither hunts cooperatively: they scavenge or hunt small prey by themselves. Domestication changed them.

Somehow, word hasn’t gotten to the dogs. Each dog has to be taught this set of parameters for his life with people. The dog learns, through you, the kinds of things that are important to you—and that you want to be important to him.

The dog’s universe is a stratum of complex odors. The world of scents is at least as rich as the world of sight.

push the present air deeper into the nose, or off through slits in the side of the nose and backward,

out the nose and out of the way. In this way, inhaled odors don’t need to jostle with the air already in the nose for access to the lining of the nose. Here’s why this is particularly special: the photography also reveals that the slight wind generated by the exhale in fact helps to pull more of the new scent in, by creating a current of air over it.

create tiny wind currents in exhalations that hurry the inhalations in.

they are continually refreshing the scent in their nose, as though shifting their gaze to get another

noses are labyrinths of channels lined with special skin tissue. This lining, like the lining of our own noses, is primed to receive air carrying “chemicals”—molecules of various sizes that will be perceived as scents.

six million of these sensory receptor sites; sheepdog noses, over two hundred million; beagle noses, over three hundred million.

The difference in the smell experience is exponential:

a dog can detect a teaspoon of sugar diluted in a million gallons of water: two Olympic-sized pools full.1

Each petal on a rose may be distinct, having been visited by insects leaving pollen

a single stem actually holds a record of who held it, and when.

And time is in those details: while we can see one of the petals drying and browning, the dog can smell this process of decay and aging.

it’s just a way of getting even more information about other dogs or animals in the area.

specialized sac above the mouth or in the nose covered with more receptor sites for molecules.

it sits above the roof (hard palate) of the mouth, along the floor of the

urine, in particular, is a great medium for

one animal to send personalized information to members of the opposite sex

we wear in odor what we’ve eaten today, whom we’ve kissed, what we’ve brushed against. Whatever cologne we put on merely adds to the cacophony. On top of this, our urine, traveling down from the kidneys, catches odorous notes from

result, dogs find it incredibly easy to distinguish us by scent alone.

To dogs, we are our scent.

another beat before my dog notices her own friend. And odors are subject to decay and dispersal that light is not: a smell from a nearby object may not reach you if a breeze carries it in the other direction, and the strength of an odor diminishes over time.

wearing someone else’s clothes, we might expect a moment of puzzlement—it is no longer “us”—but our natural effusion will soon give us away.

It doesn’t take very much of our odor: some researchers tested dogs using five thoroughly cleaned glass slides, to one of which a

placed outside on the building roof for a week, exposed over the course of the seven days to direct sun, rain, and all manner of blowing debris, the same dog was still correct on almost half

but by noticing very small changes in odor.

dogs don’t just notice a smell. They notice the change in a smell over time.

roles, to keep the scent fresh.

identify individuals by odor, they can also identify characteristics of the individual. A dog knows if you’ve had sex, smoked a cigarette (done both these things in succession), just had a snack, or just run a mile. This may seem benign: except, perhaps, for the snack, these facts about you might not be of particular interest to a dog. But they can also smell your emotions.

likely that dogs do smell fear, as well as anxiety and sadness.

dogs are skilled readers of our behavior.

there is sufficient information in our posture and gait for a dog to see it, too.

next to the smells; they weren’t rewarded when they didn’t. Then the scientists collected the smells of cancer patients and patients without cancer, in small urine samples or by having them breathe into tubes able to catch exhaled molecules.

the dogs could detect which of the patients had cancer. In one study, they only missed on 14 out of 1,272 attempts.

Urine marking, as this method of communication is called, conveys a message—but it is more like note-leaving than a conversation.

Most marked spots are high or prominent: better to be seen, and better for the odor in the urine (the pheromones and affiliated chemical stew) to be smelled.

for females, sexual readiness, and for males, their social confidence.

only 20 percent of the markings were “territorial”—

to leave information about who the urinator

often he walks by this spot in the neighborhood, his recent victories, and his interest in mating.

becomes a community center bulletin board, with old, deteriorating announcements and requests peeking out from underneath more recent posts of a...

individual-dead-fish-in-individual-sweatsock odors for each individual dog. These anal sacs also release involuntarily when a dog is afraid or alarmed.