What are dogs thinking?

The enthusiasm is partly built in. Mutual eye contact between a dog and its owner raises oxytocin in both of them - a feedback loop that does not happen between wolves and people, and one of the clearer signs of what domestication actually changed.

They also read us better than almost anything else does. Dogs follow human pointing without training, which chimpanzees largely fail at, and puppies manage it before they have had much human contact at all.

The face that gets you is a muscle wolves do not have. Domestic dogs carry a small muscle above the eye that raises the inner brow and makes the eye look larger and more infant-like. Wolves have only a scrap of it. Dogs that produce the movement more often are rehomed faster from shelters, which is the mechanism showing its working.

Smell is not a better version of our sense, it is a different instrument. A dog has on the order of two hundred million olfactory receptors against roughly five million in a person, plus a dedicated patch of nasal tissue that routes sniffed air away from the air being breathed. Smelling and breathing are separate jobs happening in the same nose.

The nostrils sample independently, which is how a dog smells in a direction. Each side reports separately, and the difference between them gives a bearing the way two ears give a bearing on a sound. The exhale vents out through the side slits rather than straight ahead, so the outgoing breath does not blow away the thing being sniffed.

A wag is not one signal. Dogs wag with a rightward bias for something they want to approach and a leftward bias for something they would rather withdraw from, and other dogs watching read the difference, staying calmer at right-biased wagging. A wagging dog is saying something specific, not simply saying yes.

The guilty look is about you, not the bin. In the study that tested it, dogs looked most guilty when they were being scolded, whether or not they had actually done anything, and least guilty when they had offended but the owner did not know. What reads as remorse is an appeasement display aimed at the anger it can already see.

Colour is reduced rather than absent. Dogs have two cone types rather than three, so the world runs on blues and yellows and red collapses toward a greenish grey. The bright red ball on the green lawn is, from down there, a low-contrast object lying in a field of roughly its own shade.

Yawning is catching, and it is catching selectively. Dogs yawn back at yawning humans, and do it more readily for someone familiar than for a stranger - the same familiarity gradient contagious yawning shows in people, which is why it gets treated as a crude marker of emotional contagion rather than tiredness.

The hearing continues past where ours stops. Dogs hear to roughly 45 kilohertz against a human ceiling near 20, and swivel each ear independently to place a source. A dog reacting to nothing in an empty room is usually reacting to something in the next one.

Sleep is fragmented by design. Dogs take twelve to fourteen hours across a day in short bouts rather than one block, and drop into REM faster than we do, which is what the paddling and the muffled barking are. A dog that sleeps all afternoon is not bored, it is keeping the schedule its body expects.

The nose print is individual. The pattern of ridges and creases on a dog's nose is distinct enough to work as identification, and some registries have used it that way. It is the closest thing a dog has to a fingerprint, sitting in plain sight on the front of its face.