Culture: Science & History
How Humans and Their Dogs Drove Neanderthals to Extinction
Pat Shipman, PhD, is a retired adjunct professor of anthropology at Penn State and an internationally recognized expert in taphonomy, the study of how living animals are transformed into skeletons, and then fossils. Her scientific training and boundless curiosity lead her to take on the intriguing question of just why Homo neaderthalensis, one of the most successful apex species of hunters who had thrived for millennium in Eurasia, would almost suddenly, anthropologically speaking, become extinct. Her hypothesis: The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction (The Belknap Press) points to the abilities of both certain wolves and our ancestors to pair up and this gave them the competitive edge in the battle of survival. It is certainly true that this wasn’t done intentionally, but such an evolutionary breakthrough resulted in an alliance that had devastating effects on not just the Neanderthals but on a long species list including the huge woolly mammoth, saber-toothed tigers and Cave bears. Could it be possible “man’s best friend” have been the Neanderthals’ worst nightmare ? Shipman’s thesis starts with Homo sapiens, who in expanding north out of Africa were not only as an invasive species, but the most invasive in history, wreaking ecologically enormous changes throughout continents. The evidence that she relies on, by a meticulous review of the most current archeological research and genomic and genetic studies, can perhaps most readily be seen in the mammoth remains megasites, where the number of kills increases almost exponentially after the first evidence of the wolf-dog–human alliance was discovered. For ten thousand years before the domestication of the wolf-dog, evidence of early humans hunting mega-fauna like mammoth is scant, but with the addition of the superior hunting and tracking talents that wolf-dogs contributed to our projectile throwing ancestors lead not only to more successful kills of large prey but insured the success of our two predatory species. As for the Neanderthal, it wasn’t just simply that humans bested them as hunters but climate change was also a key contributing factor: but the combo of the alliance of the apex predators with the ice age ensured their extinction, so goes evolution. As Shipman notes about the Jagger Principle, “… the immortal words of Mick Jagger (yes that one) and Keith Richards are the best statement I know of to describe evolution. Things don’t stay the same; you can’t always get what you want; but with a little flexibility, you might get what you need to survive.” This is truly a fascinating and thought-provoking book, and Shipman presents a compelling argument for how canines and humans proved their flexibility and how this could have been the main reason that we survived and the Neanderthals didn’t. But drawing upon the wisdom of another ’60s duo, we also got by with a little help from our [first] friends. See the following interview with Dr. Shipman to learn more.
Bark: How long did it take humans, once they migrated out of Africa, to team up with wolves, a species that was unknown in Africa?
Pat Shipman: There were wolves in North Africa, but my guess is that humans did not team up with them but rather, based on genetic information, with European wolves. The earliest humans in Europe date to perhaps 42,000 years ago. The earliest wolf-dogs we know at present show up about 34,000 years ago (or about 37,000, if the raw radiocarbon date is calibrated for irregularity in the deterioration of C-14). Thus, it may have taken 6,000 years, or less—I seriously doubt we have found the first wolf anyone ever attempted to domesticate.
BK: What environmental reasons led to this amazing partnership?
PS: There were many different predators in Europe when modern humans arrived; competition for prey was considerable, and even worse once humans came on the scene. The idea of domesticating any animal was completely unknown, but somehow— probably by accident—some wolves began cooperating with some humans because the alliance benefited both.
They caught more prey, faster, with less risk to canine or human, which meant more energy for reproduction. Wolves had a set of skills for hunting in packs: speed, keen ears, a very keen sense of smell, sharp teeth and claws. Early humans were much slower, had lousy senses of smell and hearing, and blunt teeth, but they had distance weapons that could kill an animal while avoiding injury from close contact. By teaming up with special wolves—wolfdogs they could capture a much wider array of animals with much less risk and less expenditure of energy. They were nearly unstoppable.
BK: You write that proto-dogs were like “living tools” to humans. Was this a mutually beneficial arrangement?
PS: Absolutely. You cannot force any animal to cooperate if it does not want to. You cannot force an animal not to be hostile to humans or to cooperate with humans if there is no benefit to the animal.
BK: Wolves are highly territorial, and may kill other wolves who come into their area. Since this was well before human settlements, humans and wolf-dogs would have traveled great distances, through other species’ (i.e., wolves’) territory. Could the advantage to the wolfdogs come from the protection offered by their human partners?
PS: Both wolf-dogs and humans were more efficient hunters through cooperation— the wolf-dogs by having hunters kill the prey from a distance after they had found it, isolated it and stressed it through charging and holding it at bay.
For wolf-dogs and humans to travel together, they must have cooperated to drive off or kill the wolf packs through whose territories they passed. Indeed, there is a marked rise in the number of wolf bones in human sites after wolf-dogs appear. I think wolves were deliberately targeted by humans in order to protect the wolf-dogs, and to protect the remains of their kills from scavengers.
BK: Why do you think that Neanderthals did not also have wolf-dogs?
PS: One quite real possibility is that modern humans had adaptations that fostered better communication with wolf-dogs and possibly (we don’t know) Neanderthals did not. For example, humans are the only primates with whites to their eyes, which makes communicating the “direction of gaze”— where you are looking—very obvious. This is a huge advantage in silent cooperative hunting. We do not yet know if Neanderthals had this adaptation or not. Assuming that they saw humans working with wolf-dogs, why Neanderthals did not steal them or make their own is unclear. Humans undoubtedly prized the canines and may have gone to great lengths to prevent them from being stolen. Maybe Neanderthals did not have the empathy and ability to understand wolf-dogs that is so necessary to a good working relationship. Maybe Neanderthals tried and just couldn’t figure out how to handle them.
BK: What do you think inspired humans to see that teaming up with wolves might give them a competitive edge? Did it have to do with their diet perhaps?
PS: I don’t think humans set out to domesticate wolves into dogs; I think it was an accident based on taking in orphaned puppies and raising them. Before working with wolf-dogs, humans were rarely able to kill mammoths or other very large game; afterward, there are sites with dozens of mammoth kills. I suspect that killing mammoths efficiently and regularly required the help of wolf-dogs, so mammoths weren’t really a preferred human food until humans had wolfdogs to help.
BK: It was interesting that the primary protein source in the bones of both wolfdogs and humans can be detected. What does that tell us?
PS: First, this sort of study tells us that, at the same site, wolf-dogs and wolves ate different prey animals predominantly. (That is a very surprising finding if my colleagues and I are mistaken and the wolf-dogs are really wolves, that would make them a very odd and distinctive group.) Second, this type of study shows us that humans may have provisioned wolf-dogs, rather than letting them simply eat whatever was left over.
BK: You say that wolf-dogs were a first, but unsuccessful, attempt at domestication; and that domestication happened several times in different areas. Are you concerned that their mtDNA (mitochondrial DNA) evidence hasn’t been found in modern-day canids?
PS: Not at all. There is as much mtDNA evidence that these identified wolf-dogs were wolves as there is that they were dogs: none. The mtDNA we have so far from wolf-dogs is unique, previously unknown. What that means is uncertain.
This particular genetic material is passed from mother to daughter to granddaughter and so on; the father’s mtDNA is not. This means that if you have a small population with an unusual mtDNA, the probability that it will go extinct in 1,000 years—much less 35,000—is very, very, very high.
It could be as simple as a few females who don’t reproduce successfully or have only males due to random chance. Also, athough we have several thousand mtDNA lineages from living animals, there are millions of dogs and wolves whose mtDNA is unknown. Maybe the sample sizes of living animals are too small and the wolf-dog mtDNA is still out there somewhere. Maybe it is simply extinct.
The standard calculation is that 99 percent of all mtDNA lineages go extinct, so we can’t conclude too much from that. I am not at all worried that the mtDNA information from wolfdogs has not yet been matched in any other group. Also, the entire wolf-dog group may well have gone extinct, with a still-later domestication of wolves into dogs. We just don’t know.
Good Dog: Behavior & Training
Short and sweet if given the choice
I recently attended one of my favorite annual events—the Interdisciplinary Forum on Applied Animal Behavior (IFAAB) conference. This is a small gathering of 30 Certified Applied Animal Behaviorists, Veterinary Behaviorists, Academics and Trainers who get together each year for a discussion of all kinds of topics related to Applied Animal Behavior. Every attendee gives a talk, and we discuss everything with enthusiasm from the first talk to the concluding remarks.
This year, fittingly, the first talk was about greetings. Camille Ward, PhD, CAAB, started things off with a talk called “What’s Up? Dog-to-Dog Greetings.” Greetings are a fascinating area of behavior because so much can happen in such a short time, and there are so many possible functions of greetings. Greeting between members of the same species serve a variety of functions from reducing uncertainty, fear and arousal to gathering information. Greetings can involve the signaling of status, increasing tolerance for being close to one another and may play a role in conflict management and reconciliation, which are important areas of behavior in social species though they have been primarily studied in primates.
Ward videotaped greetings between pairs of dogs at a local dog park in Ann Arbor, Michigan and analyzed the behavior that she observed. When she watched the behavior in the greetings, she collected data on a large number of behavioral details. (Videotaping is a common tool in behavioral research that allows scientists to gather more data than is possible when doing it live, and also takes so much time that it prevents scientists from taking over the world or even having a life because it keeps them too busy for such undertakings.)
In this study, 52 dogs were recorded, in 26 greetings. Each dog was only observed in a single greeting. Ward recorded whatever greetings happened to occur at the dog park, although she specifically avoided greetings when a dog first entered the park. She was interested in pairs of dogs greeting and when a dog first arrives, he is often mobbed by other dogs. Pairs of interacting animals are called “dyads” in the animal behavior literature, and the dyad was the unit of study in this project.
For each dyad, Ward noted which dog initiated the greeting or if it was a mutual approach. She noted the relative sizes of the dogs and whether play or aggression followed the greeting. Other data included whether each dog’s overall body posture was high, neutral or low both at the beginning and the end of the greeting, and if both dogs participated in the greeting by sniffing the other dog.
One of the most interesting and practical results from this study was how short the greetings were. When dogs are off leash and free to choose, they don’t hang around interacting for a long time. The greetings Ward observed were typically in the six to eight second range, which is very brief. It’s certainly a lot less time than we spend talking with our human friends when we run into them on dog walks. When that happens and our dogs also greet, they are forced to be in close proximity to the other dog when that is not what would happen if they were doing things their own way. Greetings are naturally short—far shorter than just about all of us experts at this conference would have predicted! We should keep this in mind if we have dogs greet on leash and not allow the interaction to extend beyond that time frame unless the dogs progress into play.
Based on Ward’s study, play is not a highly likely outcome of many greetings. Only six of the 52 greetings (twelve percent) she recorded resulted in play. Perhaps we should consider that many dogs want to meet and greet one another, but don’t want to engage in play as often as many of us expect. None resulted in aggression, which is encouraging, but that rate might be higher in a population of dogs that are not at the dog park as some people wisely choose not to take dogs prone to aggression to the dog park.
Greeting were either reciprocated or unreciprocated. In a reciprocated greeting, both dogs were involved in the interaction and showed similar behavior—e.g., both dogs sniffed each other. With an unreciprocated greeting, only one of the dogs sniffed or investigated. The other dog ignored or showed little attention to the greeter.
Large weight differences usually involved the heavier dog initiating the greeting. When weights were closer between the two dogs, involvement by both dogs was more common. Over 80 percent of the greetings were initiated by only one of the dogs. This pattern suggests that dogs are using greetings as a way to assess other dogs.
If you have observed your own dog greeting other dogs, does his behavior match up with what Camille Ward documented in her study?
Good Dog: Behavior & Training
Dogs who excel often do so in many tasks
Are dogs smart like people are smart? That is the question posed by researchers at the London School of Economics. They weren’t looking into whether dogs are as smart as people, but rather if they are smart in a variety of ways like people are.
When people take IQ tests, they tend to perform at a similar level across various tasks. If they do well in one area, they typically also shine in others. Are dogs the same way, showing a similar structure to their intelligence? By creating a dog IQ test of sorts with several components, the authors of, A general intelligence factor in dogs sought an answer to this question. They study was done with 68 working Border Collies to eliminate breed differences and to minimize differences in upbringing.
The tests performed on the dogs investigated their abilities to navigate barriers to get to food, to determine differences in quantities of food, and to follow a human gesture indicating the location of food. The combined tests took about an hour for each dog.
The general conclusions of the study suggest similarities between the structure of human and canine intelligence. Specifically, just like in people, there was individual variation and dogs who did well on one test were more likely to succeed at other tasks. Dogs who were quick at solving problems were also more accurate.
I think it is very interesting that we have moved away from the idea of “intelligence” as a single factor in humans, but researchers are searching for such a unified concept in dogs. Years ago, people spoke of general intelligence in humans as a separate thing than talents such as social skills, emotional connectedness and athletic or musical or artistic abilities. Now, we are more inclined to discuss people’s emotional or social intelligence or musical IQ, and more likely to discuss factors that are included in intelligence (like problem-solving ability) by being specific about them.
The main result of this study—that certain abilities in dogs such as negotiating detours, assessing quantities of food, responding to human gestures and solving problems quickly tend to be linked—is very interesting. I wish the authors would have focused on the links between the specific tasks they studied instead of generalizing to the point of putting every ability into one category called intelligence. What is going to happen if future studies suggest that a particular trait or ability is found to have no correlation to the others? Will it be considered irrelevant to intelligence, in its own special category or will it pose a problem to the concept of a general intelligence?
That said, I consider this an excellent study. It clearly shows that some individual dogs consistently have better success when asked to solve problems to accomplish various tasks. Very few studies have looked at how dogs differ from each other in this way. More studies on individual differences in cognitive ability are needed and I look forward to learning more about how dogs’ minds work as researchers continue to pursue studies comparing individuals’ abilities.
Good Dog: Studies & Research
Superior Senses: Hearing
Floppy, folded, small, large—dogs’ ears come in many shapes, but they all serve the same purpose: as funnels for sound. Did you know that at least 18 muscles work to tilt, raise and rotate these furry appendages, helping the dog identify and capture sounds from different directions? Here are a few fast facts about canine ears and hearing.
Sources: Alexandra Horowitz, Inside of a Dog; Bruce Fogle, Dogs; DVM360.com; hypertextbook.com; aspcabehavior.org
Good Dog: Behavior & Training
It influences adult behavior
“Tell me about your mother.” This phrases, so common in therapy, all but assumes that whatever is going on with someone can be traced back to the mother. Was she a good mother—attentive, patient, nurturing? Was she less than stellar—harsh, uncaring, neglectful? Whatever she does, you can bet her offspring’s behavior will be considered a result of her actions, and that doesn’t just mean in people. It’s old news that maternal care affects primates and rodents, but a new study investigated the phenomenon in dogs.
The authors of “Levels of maternal care in dogs affect adult offspring temperament” investigated the influence of the mothers on the behavior of adult dogs. Researchers looked at 22 litters of German Shepherd Dogs bred to become Military Working Dogs with the Swedish Armed Forces. The 94 puppies in the study were all continuously videotaped with their mothers during the first three weeks after birth. Videotapes were analyzed for many variables, such as the amount of time that the mother had her paws in the box with her puppies, time that she was in physical contact with at least one puppy, time she spent nursing, time she spent licking puppies, and the number of times she sniffed, poked or moved a puppy around using her nose. (Litter size was accounted for in the statistical analysis.)
When the puppies were 18-months old, they were evaluated with the Swedish Armed Forces’ standard temperament test. Dogs were assessed for their reactions to a number of situations, including social and cooperative ones with humans as well as potentially scary stimuli such as loud noises. Not surprisingly, the main result of the study is that researchers found an association between the mothers’ behavior and the behavior of her adult offspring.
Mothers were consistent over the course of the study regarding the time they spent interacting with their young. The amount of interactions that mothers had with their puppies was a really important factor associated with the behavior of these individuals as adult dogs. Specifically, puppies whose mothers had a large number of interactions with them were more socially engaged with humans as adults, more physically engaged with them, and scored higher on tests for aggression. Based on the paper, it's not clear what is meant by "aggression" or whether the association with maternal care is a positive or a negative one. (It's also not clear whether "aggression" was considered a desirable trait for these working dogs.) Confidence of the adult dogs was the fourth category of behavior measured, but no association was found between confidence and level of maternal care.
There are many factors to consider when choosing which dogs to breed in any situation, including working dog programs. This study suggests that there are benefits to paying attention to maternal care behavior when choosing which females to breed. That is, more attentive mothers are an important piece of successfully breeding dogs with desirable traits, and females who are good mothers should be considered an asset to any breeding program.
Good Dog: Behavior & Training
Familiarity affects their generosity
Do dogs act in a way that offers no benefit to themselves, but helps out other dogs? A new study called Familiarity affects other-regarding preferences in pet dogs addresses this question. The term “other-regarding” comes from the field of economics. Actions based only on the material benefit to oneself are called “self-regarding.” Actions that take into account the effects on other individuals are called other-regarding, and are often based on kindness or a sense of fairness.
In the experiment, researchers investigated dogs’ willingness to give food to other dogs. Donor dogs had the opportunity to move a tray that put food within the reach of a receiver dog or to move an empty tray instead. The donors did not receive food or any other tangible reward for giving food to the receiver. The major finding of the study was that dogs were more likely to give food to dogs that they know—their friends—than unfamiliar dogs.
The reason this is so interesting is that most research into this sort of social behavior has been conducted on primates. Little is known about cooperation and other prosocial behavior in other groups. Dogs are an obvious choice for such a study because they are social. Social animals often behave in altruistic ways, perhaps because of the possibility of a potential future benefit. In other words, evolution may have led to kindness towards others because of the benefits to individuals of trading acts of giving over the long term. That could explain why donating food to friends was more common. Those are the individuals who are most likely to be in a position to return the favor another time, making it a good investment for the donor dogs.
Good Dog: Behavior & Training
Recent research contradicts prevailing wisdom
It’s hard to make sense of the great number of contradictory studies about the effect of black coat color on the time it takes for shelter dogs to be adopted and the likelihood of them being euthanized. There have been many studies suggesting that having a black coat is bad news for shelter dogs, and some suggesting that black fur is not important in these ways.
It continues to be reported in the media that it is hard to adopt out black dogs, and many spokespeople for shelters and rescues discuss this at length. Yet, the data are not consistent across studies. One study called Investigating the role of coat colour, age, sex, and breed on outcomes for dogs at two animal shelters in the United States that came out recently in the journal Animal Welfare is one of the studies I take the most seriously. The researchers conclude that while age, sex and breed affect adoptability and likelihood of euthanasia, having a black coat color does not.
There are a number of reasons why I think highly of this research. It includes data from over 16,000 dogs from two shelters during a four-year period, which is longer and larger than most studies of its kind. One shelter chooses which dogs it admits and one has an open admission policy, meaning that it takes in any dog that arrives at its doors with no selection based on age, appearance, medical issues or behavior. The data include how long each dog was available for adoption, and whether or not the dog was eventually adopted, was euthanized or died in the shelter. Some studies have included the time that dogs were held for various reasons but not available for adoption, which could introduce biases against black dogs. It looked at euthanasia rates as well as the number of dogs of different colors that entered each shelter. It considered breed, age and size as well as coat color.
It may sound like an obvious way to conduct research, but this study looked at actual data from shelters instead of considering opinions on black dogs in interviews. The difficulty of adopting black dogs that is commonly reported in the media is often based on a study that interviewed people working in shelters and rescues. A majority of the people in that study reported that large black dogs were more difficult to place than other dogs. This is problematic because of the opinion aspect of the study and because of the lumping of size and coat color.
Despite the mixed findings across studies about the adoptability of black dogs, it is no surprise that there is a perception of bias. A number of studies have shown that people have a negative view of black dogs, considering them less agreeable, less conscientious and less emotionally stable than dogs of other colors. Perhaps more alarming, another study found that people selected large black dogs as representative examples of dangerous and aggressive animals. In support of negative views of black dogs, another study found that people were more likely to change their path in response to a black dog than in response to a pale dog, regardless of size. Not surprisingly, there are contradictory studies in this area, too. For example, one study found that people considered black poodles friendlier than white poodles.
Overall, this recent study concluded that the dogs who were more likely to be euthanized than expected if such decisions were random were dogs that were 10-12 years old, male dogs, members of bully breeds, and brindle dogs. The length of time a dog had to wait to be adopted was also affected by many factors. The dogs who were adopted most quickly were females, young dogs, yellow, grey or black dogs, and terriers or toy breeds.
There are so many factors that can influence intake and euthanasia decisions by shelter staff and adoption choices by guardians. The idea that black dogs are difficult to adopt, though the data have been so variable on this point, may actually influence people into adopting a black dog. Many adopters prioritize choosing a dog who may not otherwise find a home, and this may mean that such people are gravitating towards black dogs.
I’m certain that there will be more research about the dogs that adopters choose, so we are sure to learn more about the effect of various factors on both adoption and euthanasia.
Wellness: Health Care
Take a Deep Breath
Somewhere in northern California, a tiny dog is still prancing around on four paws thanks to hyperbaric oxygen therapy (HBOT). Unbeknownst to the dog’s owner, a piece of string had become wrapped around his paw, hidden in the dog’s dense fur. As circulation in the paw slowed down, skin and tissue began to slough off. By the time the owner realized what was happening, the paw was in such bad shape that the little dog’s vet, understandably, recommended amputation. The owner, however, wanted to try to save it. After a strict regimen of cleaning and dressing changes failed to promote significant improvement, the dog was referred for HBOT treatment.
Deep-sea and scuba divers have long used HBOT to combat the bends, and in the medical arena, it has been employed for more than 50 years to help people recover from serious infections and hard-to-heal wounds, among other ailments.
Now, this technology is being utilized to help companion animals and horses with conditions as varied as head and spinal-cord trauma, intervertebral disc disease, wounds and burns, infections, and inflammatory conditions.
The general theory behind HBOT is that it promotes healing by raising oxygen levels in the blood, allowing oxygen to diffuse into tissues at distances three to four times further than usual. Gary Richter, MS, DVM, medical director of Holistic Veterinary Care and Rehabilitation Center, Oakland, Calif., is among those who use HBOT in their practices. According to Dr. Richter, “When there’s inflammation, damaged tissues or injury, lack of oxygen is very commonly the limiting factor. By increasing the amount of oxygen delivered to tissues, we are stimulating these patients’ own healing abilities—immune systems, stem cells—to begin the healing process where other types of conventional medicine might not be able to achieve that goal.” (The dog with the damaged paw was treated at Dr. Richter’s clinic.)
Typically, HBOT treatments last about an hour and are given one to two times daily. A patient is placed in a hyperbaric chamber and breathes 100 percent oxygen at 1.5 to 3 times normal atmospheric pressure. The total number of treatments required depends upon the condition and how the patient responds. Being enclosed in the chamber doesn’t seem to distress the dogs or cats who use it; many reportedly go to sleep during treatment. Dr. Richter thinks that for the patient, it’s mainly boring; “as far as the animal’s concerned, nothing’s happening.” The cost and protocol are the same no matter how large or small the patient.
The therapy has essentially no side effects, although Dr. Richter says that it’s also important to select HBOT candidates appropriately. Dogs or cats with some types of respiratory problems or who are predisposed to specific types of seizures need to be evaluated before undergoing the therapy.
And sometimes, says Dr. Richter, the therapy may have positive side effects. Take, for example, the case of a cat with inflammatory bowel disease (IBD) so severe that she required a surgically implanted feeding tube. The surgical site became infected with Methicillin-resistant Staphylococcus aureus (MRSA), a bacterium responsible for several difficult-to-treat infections. HBOT was used to help the site heal and resolve the MRSA, but as a side effect, her IBD improved to the point that she no longer required intensive medical monitoring.
Despite being approved for use in humans for an array of medical conditions, HBOT is not without its skeptics, who say that the lack of clinical trial data supporting its claims puts it into the realm of experimental. However, based on the human experience, it would seem that HBOT has the potential to become another valuable tool in the veterinary health-care toolbox.
Good Dog: Behavior & Training
Do dogs prevent anxiety?
Kids who are asking their parents for a puppy this season have a convincing new argument to try. A recent study ("Pet Dogs and Children’s Health: Opportunities for Chronic Disease Prevention?”) reports that kids who live with a dog are less likely to be anxious than their peers living in homes without dogs. Researchers evaluated 643 children for signs of anxiety. They found that only 12 percent of kids who have dogs met the clinical criteria that would prompt health care professionals to further screen for anxiety. This was in contrast to 21 percent of kids without dogs who met those criteria.
Despite the way this study has been reported in the media, the authors of this study do not claim that there is a causal relationship between having a dog and lower levels of anxiety in children. Sure, if you are reading this, you are all but certainly a dog lover and inclined to see the benefits of being with dogs. There’s plenty of scientific evidence to back you up if this where you stand. Being with dogs can lower levels of cortisol (which is associated with stress), decrease blood pressure and heart rate, and increase levels of oxytocin (which is associated with social bonding.)
The study highlights the correlation between living with a dog and a lower likelihood of anxiety in children, but makes no claims about why the association exists. It is entirely possible, for example, that people who are less anxious by nature are more likely to have dogs, and their children just happen to share a lower likelihood of anxiety. Or perhaps people with children tend to get dogs only when their lives are not too stressful, which means that the people with and without dogs vary in their anxiety levels for reasons that are not related to having dogs.
It seems highly possible that living with a dog lowers the risk of anxiety in children, perhaps by alleviating loneliness and separation anxiety or by facilitating social interactions. Still, it’s important to understand that the links found in this study do not show the presence of the dog to be the key factor.
While I would not recommend that anyone rush out to acquire a dog for the sole purpose of lowering their children’s chances of developing anxiety, kids might try to convince you to do exactly that. They may have a point.
Good Dog: Behavior & Training
Links between canine lateralization, behavior and emotion
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?
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.
Determining Paw Preference
Strength of Lateralization
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.
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).
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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.
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