Close up of dog tail

Does that wagging tail really mean that he’s happy? Don’t count on it. As is often the case with people who we think we know, there’s a lot of misunderstanding going on between man and his canine best friend.

It’s certainly not for a lack of effort on the dog’s part: Recent studies have shown that our faithful companions can track human eye movements, sniff out diseases — sometimes before our doctors do — and wag their tails differently for their owners.

But since dogs haven’t mastered English yet, there’s a good deal of mind reading required when it comes to understanding canines.

“With dogs and owners, it is not so much a dialogue but a monologue,” says Anders Hallgren, a Swedish animal psychologist and the author of The ABCs of Dog Language. “Owners take over the communication and don’t listen or don’t read what the dogs are saying.”

From half-moon eyes to demand barking, there are myriad ways that our four-legged wonders try to communicate with us every day.

The Eyes Have It

“If you look at dogs’ eyes, you can see so much,” says Hallgren. “There are so many muscles around each eye that they can quickly change from attack mode to flight mode to ‘I’m starving mode’ — especially if they’re near the table.”

One commonly misinterpreted eye movement is what animal psychologists call "half-moon eyes."

“You often see this when children hug a dog,” says Karen Pryor, author of Reaching the Animal Mind. “The head is lowered and turned away, and the whites of the eyes are showing, which is like us clenching our fists because we hate what’s happening to us."

In addition to telegraphing their own needs, dogs also seem to have an ability to read our minds. According to a new study, this isn’t actually doggie ESP, but the result of some rather keen powers of observation.

Closeup of Yorkshire Terrier eyes

Researchers recently recorded dogs tracking humans’ eye movements, as if trying to decode intent — a phenomenon akin to a baby watching his parents. “Dogs are receptive to human communication in a manner that was previously attributed only to six-month-old human infants," coauthor Jozsef Topal told Discovery News. “They can play the role of being a child substitute.”

And, just like babies, our favorite fuzz balls may even be able to read human expressions.

In a study conducted at Azabu University in Japan, dogs were shown photos of their owners either smiling or with neutral expressions on their faces. The canines were trained to only identify photos of smiling owners. When they were shown photos of non-owners, many of the dogs still flagged pictures of humans who were smiling.

This behavior isn’t necessarily innate to canines — who usually equate bared teeth with aggression — but it’s one that may have been learned thanks to constant contact with humans.

Wag This Way

What is that propeller of a tail really trying to tell you? Truthfully, it can signal anything from elation to aggression.

“A lot of trainers will tell you that a truly happy dog will wag his tail in a circle,” says Pryor. “If a dog does that, you should feel very complimented.”

But it can also be a common sign of aggression. “There’s a lot of misunderstanding,” says Dr. Jules Benson, BVSc MRCVS, a veterinarian at the Doylestown Animal Medical Clinic and a member of the Board of Trustees for the Pennsylvania Veterinary Medical Association (PVMA). “A lot of slow tail wagging is exploratory and often a sign of ‘I’m excited or scared,’ while lateral movements are a sign of indecision. Bouncing up and down? That’s a happy tail.”

As for the direction of a tail wag, well, that all depends on who’s approaching. According to a recent New York Times piece, when dogs feel positive about someone, their tails wag more to the right. When they have negative feelings, the wagging is biased to the left.

Just don’t be surprised if it’s hard to see evidence of this at home. “The degree of the movements was statistically significant but hard to observe,” says Dr. Benson. “The researchers had to rely on stop-motion photography.”

Sensitive Sniff Test

As the old saying goes, the nose knows — especially with pooches.

“Dogs are capable of sniffing everything from drugs to electricity,” says Dr. Michael A. Selmer, DVM, of the Advanced Animal Care Center in Huntington, N.Y. “Recent studies suggest that they may even be capable of detecting human illnesses, like epilepsy and cancer, with their noses.” In fact, when asked to sniff out colon cancer in a recent study, canines were 90 percent accurate or “just below what a colonoscopy is able to do,” adds Dr. Benson.

So what makes Fido such a super sniffer? According to Dr. Selmer, a dog’s olfactory glands are about four times larger than ours, and their brain is about 10 times smaller. “This means that your dog’s brain has 40 times as much of its brain devoted to smell than we do,” he says, adding that a dog’s sense of smell is estimated to be 100,000 times better than his human owner.

This is partly why dogs are often attributed psychic powers — but it’s more that their noses know no bounds.

A dog can smell fear — or at least the pheromones that are released when we’re afraid, says Dr. Selmer. “Sniffing chamomile can make your dog calmer, whereas peppermint can make him more excited,” adds Dr. Selmer. “All these things make him one special creature.” (Though be sure to speak with your own vet before  trying any kind of aromatherapy with your dog.)

Can You Hear Me Now? The ABCs of the Canine Bark

Dog barking at a tree

Barks are expressions of emotion,” says Pryor. “An animal can bark because he’s alarmed, and that’s the ‘stranger danger’ bark. And an animal can bark because he’s calling for help.”

And then there’s that most domesticated of barks: “Animals often learn to bark to get you to do something,” says Pryor. “That’s called ‘demand barking,’ and this is definitely something you don’t want to encourage.”

Howling, on the other hand, is a more primitive habit. “That’s a more instinctive type of behavior,” explains Hallgren. “Dogs are born with it.” Baying at the moon — or a neighbor’s Cockapoo — may hark back to an innate need to strengthen pack bonds. Wolves, for instance, will wake up and howl in unison before heading off to hunt.

One thing that always precedes howling is what experts call a “key stimulus,” such as another dog or a fire engine. In other words, there’s usually a good reason why a dog lets loose.

But if he starts to howl when no one is home, it may be your behavior that needs changing. “The dog is calling you and asking you to come home,” says Hallgren. “It’s a symptom that he feels lonely.”

Of course, there is one ubiquitous bark that can (and should) be corrected — barking at the door. “This is a bark we treat totally wrong,” says Hallgren. “We rush after the dog, and try to silence him.” The problem with this approach? When the dog hears the doorbell, he wants the whole pack to go with him because he knows there’s strength in numbers.

Instead, Hallgren advises dog owners to equip everyone who passes through the door with a treat, so that the dog learns to equate the doorbell with a reward for good behavior. In other words, take a wag the dog approach to bark management.