How well do we know man’s best friend? (Andrew Burton/Getty Images)

Alexandra Horowitz is the principal investigator in the dog cognition lab at Barnard University and the author of “On Looking” and “Inside of a Dog.”

Why is America fascinated by dog shows? The Westminster Kennel Club show, held at Madison Square Garden this week, attracts will attract millions of television viewers, and that could be because it blends the novel and the familiar. Spectators may goggle at unusual breeds, such as the proud, long-eared treeing Walker coonhound or the shepherding puli, nearly hidden by its heavy dreadlocked coat. At the same time, we all have experience with dogs and a sense that we understand them. Some of our commonly held beliefs, though, deserve reexamination.

1. “Best in show” is the best breed all around.

Since the Westminster Kennel Club was formed in 1877, its mission has been to “increase the interest in dogs, and thus improve the breeds.” Certainly, interest in dogs has increased over the past 137 years. But the effort to improve breeds has created a problem: The “best in show” and the runners-up may not be the healthiest dog breeds out there.

Many well-bred purebreds have genetic disorders that no one hoped for or expected. For instance, to meet the breed standards, pugs and bulldogs have been bred to have squat heads, which severely restrict breathing. The English bulldog’s body is so altered that it cannot mate or deliver puppies without human intervention. The ridge that gives the Rhodesian ridgeback its name often co-occurs with a neural tube defect. The Cavalier King Charles spaniel is prone to syringomyelia , a painful swelling at the back of the skull.

These are the unavoidable results of breeding individuals from a small, closed gene stock. They can be corrected by breeding outside the line — which might betray the principles of a breed standard, but the dogs would be better for it.

2. You know what you’re getting when you get a purebred dog.

This is the sort of thing people sometimes say to explain why they want a pedigreed dog rather than a mixed breed. And it’s true that the breed standards encourage the perpetuation of lines of dogs with particular characteristics. According to the American Kennel Club, the golden retriever is supposed to be “friendly, reliable, and trustworthy,” the poodle “intelligent,” the Rottweiler “self-confident.”

But some people treat the AKC’s listing of dog breeds and their characteristics as a catalogue. They comparison-shop one breed’s features against another’s, and they forget that dogs are not fixed products. As with people and every other animal, the genome interacts with the environment to create the individual. A timid golden retriever puppy who gets out of a fearful encounter by biting could learn to become a regular biter of anyone who approaches suddenly. A poodle who is given no stimulation may seem less intelligent than a nuisance.

No one should get a dog based on breed specs alone.

3. Dogs are the domesticated descendants of wolves.

The contemporary gray wolf, Canis lupus , is indeed the cousin of the domestic dog. But the latter did not descend from the former. All the evidence, genetic and otherwise, points to a shared ancestor: some ancient wolflike animal , now extinct, from which they both evolved tens of thousands of years ago .

The distinction is important. In some cases it is appropriate to look at wolf behavior to understand dog behavior, and vice versa. Yet there are significant differences between the species. For instance, wolves use eye contact as a threat, whereas domestic dogs are able to make eye contact with people in a way that encourages our feeling of mutual understanding.

With so many years of evolution between them, we can be sure that no dog, let out of the house, is going to “return” to being a wolf — nor would its offspring, nor its offspring’s offspring.

4. You need to be the alpha with your dog.

Perhaps the most influential tenet of the Dog Whisperer, Cesar Millan, is the notion that in the dog-owner relationship, the owner needs to be the leader of the pack. Ignore this principle, proponents say, and the dog in your house will try to displace you as the pack’s alpha.

But this conception of “pack” and “alpha” is inapplicable to dogs and humans. The idea is rooted in legitimate research — but the conclusions of that research hold only for the study population: wolves, most of them adolescent males, held captive in a small enclosure. In the mid-20th century, animal behaviorist Rudolph Schenkel determined that these wolves established a hierarchy in which certain individuals ate and mated first, and he suggested that other members of the group were in a perpetual struggle to take over the alpha position.

But wolf behavior in prisonlike conditions doesn’t extend to wolves in the wild — or to dogs. Indeed, researchers have found that wild wolf packs are typically family groups. The parents are in charge, but only in the same way that I am in charge of my son. My son doesn’t try to overthrow me, nor do younger wolves try to overthrow their parents. Studies of free-ranging dogs have found that they don’t form strict dominance hierarchies, either. They do stay together, but they don’t hunt cooperatively like wolves do.

It makes sense to be a leader for your dog insofar as you make your expectations clear. But trying to dominate your dog, lest he dominate you, is like taking a parenting lesson from “Lord of the Flies.”

5. You can tell your dog is guilty as soon as you walk in the door.

Many people believe that dogs feel guilty for doing something wrong and that we can tell this from their body language. That’s the assumption in the viral video of the yellow Lab Denver, who grimaces after she’s accused of eating cat treats. The video has been viewed more than 33 million times on YouTube — and has inspired “Denver’s guilty bandanas ” and “The Adventures of Denver the Guilty Dog,” a planned series of children’s books.

The problem is, the “guilty look” is not what it seems. A dog may plaster his ears against his head, turn away, wag his tail low between his legs or just take off when accused of a misdeed. But in research I did where owners confronted dogs both guilty and innocent of eating a forbidden treat, I found one clear result: The “look” happened most when dogs saw scolding, questioning or angry owners, whether the dog was guilty or not. Later work replicated this finding. And separate research has found that owners are right only 50 percent of the time — the equivalent of random chance — when asked to guess, by looking at their dogs, if the dogs had transgressed in their absence.

The “guilty look” would be better called the “submissive look,” as in, “Don’t punish me for whatever it is you think I did.” We don’t yet know whether dogs actually feel guilt, but we shouldn’t assume that they do.

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