A few years ago, dog trainers and behaviorists renewed their love affair with tail-wagging, constantly checking to see whether dogs were wagging their tails higher to the right or to the left. Our awkward attempts at positioning ourselves to observe this behavior were surely entertaining to others. Why were we so eager for the information conveyed by these asymmetrical tail wags? Because they indicate dogs’ differential use of the left and right hemispheres of their brains and are, therefore, a window into their emotions.

The study of asymmetrical tail wagging that prompted our collective interest (Quaranta et al. 2007) found that differences depended on what inspired the wags in the first place. Dogs wagged higher to the right when greeting their guardians. The same right-side bias was seen in response to unfamiliar people, although the wags were lower overall. In response to cats, there was little wagging, but it was still higher to the right. In the tests, the only stimulus to which dogs’ wags had a left-side bias was an unfamiliar, confident dog.

Left or Right?
Asymmetrical tail wags reflect the way the two sides of the brain process information and affect the body. The right hemisphere controls the left side of the body and the left hemisphere controls the right side. When dogs wag their tails to the right, they are engaging the muscles on the right side of their body more actively than those on their left; this demonstrates greater involvement of the left hemisphere of the brain.

The left hemisphere is activated when the brain is processing positive experiences associated with emotions such as happiness, affection and excitement, as well as anything familiar. The right hemisphere takes precedence when processing sadness, fear, other negative emotions and novel things.

This link between emotions and sides of the brain came to light in studies of humans. Ahern and Schwartz (1979) found that people who were asked questions that elicited either positive or negative emotions responded in accordance with this principle. They looked to their right (showing left brain hemisphere involvement) in response to questions that elicited positive emotions, but looked to their left (showing right brain hemisphere involvement) in response to questions that evoked negative emotions.

Individuals—canine or human—who favor the left paw or hand more often use the right hemisphere of their brain, while right-pawed and right-handed individuals have a more active left-brain hemisphere. Studies have shown differences between right-pawed and left-pawed dogs. They have also revealed that dogs who are ambilateral—who don’t have a paw preference—are different in predictable ways from dogs who strongly prefer one paw over the other.

Lateralization research, an active area of study, informs our understanding of emotions and behavior. Though dogs and people are common study subjects, similar patterns have been found in fish, amphibians, reptiles, birds, and primates and other mammals.
We now know that the significance of brain lateralization, handedness and paw preference extends far beyond matters of scissors and can-openers (people) and learning to shake (dogs). There are strong links between paw preference, the strength of that preference, and the behavior and emotional life of dogs.

Determining Paw Preference
In humans, we identify hand preference based on which hand a person uses to eat, write and so forth or by seeing who keeps their arms tucked in tight when eating at a small round table. (It’s the lefties, because they are used to colliding with the righties next to them if they don’t act to prevent it.) In dogs, most determinations are based on the “Kong test,” in which dogs are observed extracting food from a Kong. Every time the dog uses a paw to stabilize the Kong, the observer records which paw was used. If the dog uses both paws simultaneously, that is also recorded. From these data, researchers determine a dog’s paw preference as well as the strength of that preference. There are approximately equal numbers of left-pawed, right-pawed and ambilateral dogs, which is different than the preponderance of righties in humans.

Paw Preference
Our dogs’ paw preferences provide insight beyond knowing which paw is used to steady a Kong. Batt et al. (2009) reported that being right-pawed was associated with lower arousal and calmer responses to novel stimuli and strangers. Schneider et al. (2013) found that dogs who were left-pawed exhibited more stranger-directed aggression than dogs who were either right-pawed or ambilateral. Many potential guide dogs fail their training—usually for behavioral reasons—and Tomkins et al. (2012) documented higher success rates of right-pawed than left-pawed dogs in training programs.

Strength of Lateralization
In addition to the effects of paw preference on emotions and behavior, the strength of those preferences also has an effect. Branson and Rogers (2006) demonstrated that dogs without a paw preference were more reactive to loud noises than dogs with a paw preference.

Batt et al. (2009) showed that dogs with stronger paw preferences were bolder and less cautious than dogs with weaker paw preferences. They were more confident, less prone to arousal and anxiety, quicker to relax or become playful in new environments, and exhibited calmer responses to novel stimuli and strangers. It turns out that we humans are similar to our best friends in this regard: People with weak hand preferences are more likely to suffer high anxiety levels and are more susceptible to both PTSD and psychosis than those with a strong handedness.

Just as being right-pawed predicted guide-dog training success, dogs with a strong lateralization (either left or right) and a low rate of using both paws in the Kong test fared better in these programs (Batt et al. 2008). The authors hypothesize that this may be because strongly lateralized and right-pawed dogs are less likely to experience high reactivity and distress responses, which are detrimental to success as a guide dog.

Sensory Processing
In studies of sensory processes and lateralization (Siniscalchi et al. 2008, 2010), dogs were simultaneously presented with identical stimuli on both their left and right sides while eating from a bowl. The direction in which they turned their heads indicated which side of the brain was involved in processing and responding to the stimulus, revealing the dogs’ emotional reaction to it. Dogs consistently turned to the right (involving the emotionally positive left-brain hemisphere) in response to the social cues of canine isolation or disturbance calls and canine play vocalizations, but tended to turn left (showing the activation of the emotionally negative right-brain hemisphere) when they heard thunder.

Dogs also turned left in response to images of cats and snakes but not to images of dogs. With repeated presentations, there was a change toward right-turning behavior, indicating that the left side of the brain and its associated positive emotions were involved. This suggests that novelty may be a factor in fear and other intense negative emotions that tend to be processed by the right side of the brain.

To understand the role of lateralization in processing olfactory stimuli, it is essential to know that each side of the brain processes the information received on the same side: the right nostril goes to the right hemisphere, the left nostril goes to the left hemisphere. Dogs started to sniff novel but non-aversive stimuli (food, lemon, dog secretions) with their right nostril and then shifted with repetition to using their left nostril, showing a change from negative to positive emotions. When presented with adrenaline and sweat from their vets (really!), dogs demonstrated a consistent bias toward the right nostril, suggesting that their emotions started, and remained, negative in response to these odors (Siniscalchi et al. 2011).

Practical Applications
Our understanding of lateralization has potential to improve our dogs’ quality of life, our relationships with them and even our success in training them. We may be able to reduce stress by approaching dogs from their right side in exams, during greetings or in any stressful situations. We can quickly see how dogs react emotionally to a variety of stimuli by attending to which way they turn, and we can observe the asymmetry in their tail wags to ascertain their emotional state. It’s possible that we can even minimize the development of noise phobias by placing dogs whose lateralization suggests vulnerability in quieter homes. We can minimize the substantial investment of time and money spent on training guide dogs by training only those dogs who have the greatest chance of completing the program.

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Love and understanding compound one another with our dogs, and lateralization is a case in point. A dear dog friend of mine is strongly right-pawed; it was pitiful to watch him attempt to learn to give a left high-five, or use his left paw to hold his Kong when he briefly had a bandage on his right paw. I used to find how hard it was for him to do anything with his left paw somewhat comical. Now I understand that this trait is part of the package that makes him the unflappable, happy, don’t-care-about-the-power-tools-running-all-day-during-the-kitchen-remodel, playful and exploratory, nothing-fazes-him kind of dog I love so much. I’m honored and overjoyed that when he greets me, his tail wags are as one-sided to the right as the rest of him.

When and how much our dogs sleep matters to us because it affects our own sleep. Most people who have ever raised a puppy know the horror of sleep deprivation, and many people caring for elderly dogs or those who are unwell are facing the same problem. Even dogs who don’t need to be taken out in the middle of the night or in the wee hours of the morning often work against the goal of an uninterrupted stretch of eight hours of restorative sleep each night.

I once had a dog who slept in every morning, and I valued that quality in him immensely.  Though I made many attempts to figure out how to transfer this quality to all dogs, I suspect he just came into the world that way. True, we did feed him healthy food and give him lots of exercise, but that surely hasn’t worked on a large number of other dogs. Still, I maintain a strong interest in learning about the variables that affect dogs’ sleep patterns, with the eventual hope that dog guardians everywhere can apply it to their own dogs for the benefit of all.

Because I am interested in canine sleep, I was interested in a study that investigated some basic aspects of dogs’ sleep patterns. The research looked into the effects of age and feeding frequency on dogs’ sleep patterns. Dogs were in one of three age ranges (1.5-4.5 years, 7-9 years, 11-14 years) and were fed either once or twice daily.

The researchers found that older and middle aged dogs slept more during the day than young adult dogs, but that was because they took more naps, and not because their naps were longer. Older and middle aged dogs also slept more at night than younger dogs because they had a longer total sleep interval at night (waking up later) and woke up fewer times during the night.

Dogs of all ages were affected in a similar manner by being fed twice daily as opposed to once a day. Dogs who were fed more frequently took fewer naps during the day, but the naps lasted longer. Dogs fed twice a day fell asleep earlier at night, but woke up earlier, too with a decreased total time sleeping at night. (The earlier waking time more than compensated for the earlier bedtime.)

>The take home message to me is that if you want more sleep, just wait until your young dog ages a little. That’s interesting when you compare dogs to humans, because we sleep considerably less as older adults than as young adults.

Have you noticed a change in your dog’s sleep pattern with age or with changes in feeding schedules?

One disadvantage of being a canine behaviorist is that so many human behaviors scare me. My heart leaps into my throat all too often when I see people performing risky behaviors around dogs. From hugging dogs and picking up dogs to sticking their faces right by a dog’s face or bending over a dog, there are plenty of gasp-worthy moments. I see people performing these behaviors and want to scream out a warning. It’s similar to the reaction I have when watching a horror movie and want to yell, “Don’t go in the house!”

I work with so many clients whose dogs have bitten someone, and as I hear the stories of the bites, the same human behaviors are mentioned over and over. I’m not saying this to blame the people, but rather to help us all learn how to lower our risk of being bitten.

Dog bites are a serious problem that we should all attempt to avoid, and among the most distressing are bites to the face. In a new study called Human behavior preceding bites to the face, scientists examined 132 incidents of bites to human faces that did not involve bites to any other parts of the body. The goal of the study was to determine the human behavior that preceded bites.

Well-know risky behaviors such as bending over a dog, putting the face close to a dog’s face and eye contact with the dog and person very close to each other did occur before many of the bites, which is no surprise. What was a bit of a shock was the percentage of times that these no-no behaviors happened before the 132 incidents in the study. In 76 percent of the bites, people bent over the dog just before the bite! In 19 percent of the cases, a bite was preceded by people putting their faces close to the dog’s face, and in five percent of the cases, gazing between dog and person at close range occurred before a bite. In no incidents was a bite to the face preceded by trimming the dog’s nails, falling on the dog, hitting the dog as punishment, stepping on the dog, pulling the dog’s hair, tugging the dog’s body or scolding the dog.

More than 75 percent of the bites to the face happened to people who knew the dog. Over two-thirds of the bites were to children, and of those, 84 percent were to children under the age of 12. Children who were bitten were with their parents in 43 percent of the cases and with the dog guardian in 62 percent of the incidents. Sixty percent of the bites were to females, and no adults were bitten by their own dogs. More than half of the bites were to the nose and lips of the person, as opposed to the chin, cheek, forehead or eye area.

All of the dogs who bit someone in the face were adult dogs, and over two-thirds of them were male dogs. In only six percent of the bites did people report that the dog gave a warning such as growling or tooth displaying prior to biting. (To me, this is the single most surprising finding in the study, and I think it’s quite possible that some people did not notice or failed to remember warnings by dogs.)

As the authors of the paper mention, this research is based on questionnaires that ask people about past events. As such, there are inherent limitations with the study. Still, the results about the frequency with which kids are bitten, the greater likelihood of male dogs biting faces than female dogs, and the finding that only adult dogs bit faces are consistent with previous research.

If you have ever been bitten in the face or seen it happen to someone else, what do you remember about the human behavior right before the bite?

With their extremes of limb and coat, purebred dogs may seem more prone to health problems. And don’t breeders even compound defects, as they tinker with uniformity? Yet the dog of many varieties, a potluck of traits, outlasts them all.

Not quite, say U.C. Davis researchers in a recent study lead by Anita Oberbauer in Canine Genetics and Epidemiology. Their analysis of health records of 88,635 dogs, both purebred and mixed breeds, tilts assumptions. So does another recent study, in which they found both populations shared similar risk for 13 inherited disorders. One condition was even more prevalent in mixed-breeds.

Purebreds, and their health records, have made it easier to explore the genetics of diseases that get passed down, the researchers say. But as we hear about the studies, the belief that purebreds are less healthy grows. In fact, many breeds have proven more prone to some diseases, like Great Danes and hip dysplasia.

In this study, they sliced the data thinner. Could particular AKC breed groups, not just individual breeds, be the source? Do the diseases arise from dogs with genomic similarities like working and herding groups? The huge pack of canines, seen over 15 years at U.C. Davis veterinary teaching hospital, showed that ten inherited conditions are more common in purebred dogs. But surprise, not all purebred dogs.

A subset of pedigreed pups tied with mixed breeds for the disorders.

The conditions include aortic stenosis (narrowing above the aortic heart valve or of the valve); skin allergies; bloat; early onset cataracts (clouding of the lens inside the eye); dilated cardiomyopathy (enlargement of the heart chambers); elbow dysplasia (abnormal tissue growth that harms the joint); epilepsy (brain seizures); hypothyroidism (underproduction of thyroid hormones); intervertebral disk disease (affects the disks of the spine, causing neurological problems); and hepatic portosystemic shunt (abnormal blood circulation around the liver, rather than into it).

With a spotlight on the ten maladies, the researchers set out to learn which canines are more at risk. Purebreds were subdivided into categories, then compared to the mixed breeds.

For three conditions common across the purebreds—skin allergy, hypothyroidism, and intervertebral disk disease—many groups had higher prevalence than the mixes. But for seven others, most purebred groups were statistically neck and neck with mixed-breeds. (Aortic stenosis, gastric dilation volvulus, early onset cataracts, dilated cardiomyopathy, elbow dysplasia, epilepsy, and portosystemic shunt).

Terrier groups even bested the mixes for one problem, having less intervertebral disk disease.

Among the purebred groups, health differences were clear. Compared to mixed breeds, terriers and toys were more likely to have two disorders. Herding and hound groups were more burdened with four conditions. The non-sporting group, where pooches ranging from Poodles to Dalmatians fit in, were more likely to have five disorders. Working breeds, animals expected to have grit and vigor; six. Worst in health: the sporting group bred for outdoor stamina. They were more at risk for seven inherited disorders.

In fact, in three categories of dogs bred for endurance—herding, sporting, and working AKC groups—aortic stenosis, the heart condition present at birth, was higher. With narrower focus, other findings emerged. The researchers say the data “suggests that most breeds in the herding group are not at higher risk”—except the German Shepherd, which other studies have also found susceptible.

And while Retrievers were more affected by aortic stenosis, another sporting breed, the Spaniel, wasn’t. For a different malady, Spaniels were the unluckiest. Epilepsy was more prevalent in herding, hound, and sporting groups, particularly the Spaniel breeds.

Early onset cataracts beset both non-sporting and sporting breeds more often.

How did all of these health glitches arise? The study mentions other research that found some diseases, like elbow dysplasia, are more frequent in dogs of related ancestral origin. The so-called “liability genes” may hail from founding ancestors of related breeds, or be the result of human error in the quest for desired traits. This study, the authors say, “may shed light on the possible origin of certain inherited disorders in domestic dog evolution.”

For the ten diseases, the analysis found some purebreds genetically healthier than others. Flipped around, mixed breeds were no healthier than certain purebreds. But both populations may benefit from the work. According to the researchers, defining the lineage associations for such disorders may bring about new therapies.

Better, it could allow breeders to weed out the responsible genes to begin with. Especially at the local level. “Whether breeding reforms will mitigate inherited disorders in mixed-breeds will depend upon the locale,” the scientists say. That is, some regions have a greater potluck of breeds within their mixed-breeds.

Still, since most mixes have purebred ancestors, they say, improvement of the genetic health of purebreds “may trickle down to mixed-breed dogs.”