Wellness: Healthy Living
Toxic chemicals also found in dog food
A long-term study conducted in Britain has found that male dogs are losing fertility, and that exposure to environmental chemicals (ECs) that have leached into the environment may be to blame.
The dogs—Labradors, Border Collies, German Shepherds and Golden Retrievers bred to aid the disabled—made an ideal group to explore the larger question of a decline in human semen quality that has been occurring since long before this study.
This twenty-six year long study, 1998-2014, was conducted by Richard Lea and colleagues at Nottingham University’s school of veterinary medicine. They collected annual samples of semen from dozens of dogs, all from the same breeding program, all healthy and well cared for. Each year, the same problem recurred; a 2.4 percent dip in sperm motility, that is the ability to swim in a straight line. In addition to monitoring semen quality, they analyzed health records, finding an increase in cryptorchidism, a condition in which the testicles fail to extend normally to the scrotum. Over the same years, fewer male pups were born than females, also there was an increase in fetal and prenatal female mortality.
And, lurking in the samples of semen and testicles of dogs obtained from neutering, it found ECs—chemicals that tamper with hormones. The chemicals include polychlorinated bisphenol (PCB), a compound banned in 1977, and diethylhexyl phthalate (DEHP). PCBs don’t readily break down while phthalates are common in a wide number of products, from cosmetics to detergent. Both chemicals are associated with fertility issues and birth defects.
In human babies, exposure to chemicals has been linked to faulty development of semen quality and cryptorchidism. According to the study, such reproductive problems often cluster in geographical areas, and so are suspected of having a common cause; exposure to hormone-disrupting chemicals is “thought to be the initiator.” To explore the same possibility in dogs, chemicals were measured in canine testes and semen taken from the same geographical area where the study took place.
Both chemicals “perturbed sperm viability, motility and DNA integrity in vitro.” The researchers concluded that the direct effects of chemicals on sperm “may contribute to the decline in canine semen quality” that parallels that in humans.
“Why the dog?” said Dr. Lea. “Apart from the fact that it is a great population of animals to work with, dogs live in our homes, they sometimes eat the same food, they are exposed to the same environmental contaminants that we are, so the underlying hypothesis is that the dog is really a type of sentinel for human exposure.”
The same ECs were found in a range of commercially available dog foods. DEHP and PCB153, “were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species.”
While the brands were not named, they are reported to be both wet and dry forms sold worldwide. The scientists don’t know how the chemicals made it into the food, but since they are not deliberate additives, they may have leached from the packaging or processing sources.
These overall findings are troubling, but they also noted that: “Amongst the dry dog food samples, one sample designed for puppies (1 to 24 months of age) had higher concentrations … relative to the other samples tested.”
Plus, while the researchers cannot say the dog food is a direct source of the ECs, the New York Times reports that "Dr. Lea said it was probably a major one."
What is known is that the chemicals wound up in dog’s testicles, where they messed with sperm motility and viability. “This may be a way by which environmental chemicals directly affect male fertility.”
While the dogs in the study were still able to reproduce, it’s hardly reassuring that, once more, the dogs who share our homes also share our diseases, unwittingly, acting as the “canary in the mine” for us.
Good Dog: Behavior & Training
Differential use of the left and right nostril
The common wisdom that dogs can smell fear doesn’t give dogs full credit to the nuances of their ability to sense emotion through their noses. A recent study titled “The dog nose “KNOWS” fear: Asymmetric nostril use during sniffing at canine and human emotional stimuli” examined dogs’ tendencies to sniff various substances with the right or the left nostril. Exploring this side bias may seem like looking at random details, but the side of the nose used to sniff something tells us a lot about the dog’s emotional reaction to the odor. The use of one side of the body indicates a differential use of one side of the brain or the other, which is a clue to the dog’s emotions.
The left side of the brain processes more positive emotions such as happiness and excitement as well as stimuli that are familiar. The right side of the brain tends to take over when a dog is processing negative emotions such as sadness or fear as well as novel stimuli. In general, the right side of the body is controlled by the left hemisphere of the brain and vice versa. However, the nose is an exception; the right nostril sends information to the right side of the brain to be processed and the left nostril sends its information to the left side. The findings of this study suggest that the pathways used to process various olfactory stimuli are dependent on more than just whether they elicit negative or positive feelings.
Eight odors were tested—four from dogs and four from humans. The four human odors were collected as sweat from donors who were joyful, fearful, physically stressed, or in a neutral situation. The joyful and fearful states were elicited by movies, and the physical stress odor was collected after donors ran for 15-minutes. The four canine odors were collected from dogs who were happy following a play session with the guardian, stressed by isolation in an unfamiliar place, disturbed by a stranger approaching the car, and dogs who were asleep. The dogs who “donated” odors were different from the dogs whose sniffing behavior was studied.
To further explore the phenomenon of side bias in sniffing, the guardians of the dogs in the study filled out a questionnaire related to each dog’s temperament. During the study, dogs were led to a video camera under which was mounted a Q-tip saturated with various odors. The videos captured the dog’s sniffing behavior so that it was possible to determine a laterality index for each dog for every odor based on the amount of time spent sniffing with each nostril. A laterality index of 1.0 indicated exclusive use of the left nostril and negative 1.0 indicated exclusive use of the right nostril. Dogs’ cardiac activity was also recorded during the tests of each odor.
I’m sure it’s the science geek in me, but I got a kick out of reading the sentence, “Results for nostril use are shown in Figure 2.” Three of the odors elicited consistent sidedness in nostril use and five of them did not. Dogs more frequently used the right nostril to sniff the canine isolation odor. They more frequently used the left nostril to sniff the human fear odor and the odor from human physical stress.
There were two ways in which the results of the questionnaire were correlated with the laterality pattern for a particular odor. The higher a guardian ranked the dog’s fear/aggressiveness to other dogs, the more likely that dog was to use the right nostril for sniffing the disturbed canine odor. This suggests that individual differences in emotional arousal and perhaps even in temperament influence asymmetries in sniffing behavior. Dogs with higher scores for predatory behavior used the left nostril more for sniffing the odor that came from physically stressed humans. This makes sense when we consider that it is structures in the left side of dogs’ brains that are involved in predatory behavior.
Dogs’ brains are every bit as amazing as their noses, as research about both of them reveal!
News: Guest Posts
An international group of scientists proposes dual domestication from wolves.
Among the many hotly debated topics related to the appearance of dogs in the lives of humans is how often and where it first occurred. In their landmark 1997 paper on dog origins, Robert K. Wayne, Carles Vilá, and their colleagues made the case for multiple origins, but many other students of dog evolution, including Peter Savolainen, a co-author on that paper, have repeatedly and strongly argued for a single place of origin.
In this week’s Science magazine (June 3, 2016) [the article is available here, gratis], Laurent Frantz of Oxford University’s ancient dog program, writing for more than a score of his colleagues from institutions around the world, presents the case for dual domestication of Paleolithic wolves in Western Eurasia and Eastern Asia. According to this hypothesis, a now extinct ancestral wolf split into at least two genetically distinct populations on opposite sides of the Eurasian continent where they encountered and joined forces with humans to become dogs.
Frantz and his coauthors pin much of their argument on analysis and comparison of the fully sequenced genome of a 4,800- year old dog unearthed at Newgrange, Ireland, to other ancient and modern dogs and modern wolves. They found it retained “a degree of ancestry” different from modern dogs or modern wolves. Using that and other evidence the researchers argue that the most comprehensive model for the appearance of the dog involves at least two domestication events 15,000 or more years ago. Frantz writes: “The eastern dog population then dispersed westward alongside humans at some point between 6,400 and 14,000 years ago, into Western Europe (10,11, 20), where they partially replaced an indigenous Paleolithic dog population. Our hypothesis reconciles previous studies that have suggested that domestic dogs originated either in East Asia (9, 19) or in Europe (7).”
I asked Greger Larson, co-director of the Oxford project and corresponding author on the paper, just what were the boundaries of “Western Eurasia,” comprised apparently of Europe and the Middle East, and “Eastern Asia?” He answered in an email that the boundaries were left deliberately vague because where wolves became dogs remains unknown, like the date itself.
In Science, Frantz writes: [W]e calculated the divergence time between two modern Russian wolves used in the study and the modern dogs to be 60,000 to 20,000 years ago.” The first number puts the dog in the time when Neanderthal was still the big kid on the European block, raising the possibility that Neanderthal had protodogs or that early modern humans came to Europe with dogs or soon allied with wolves. Either of the first two prospects must have set off alarms in some circles for Frantz cautions that those dates should not be taken as “a time frame for domestication” because the wolves they used may not have been “closely related to the population(s) that gave rise to dogs.”
Fundamentally, this paper is at once a bold attempt to come up with a workable hypothesis to explain the appearance of the dog in human affairs and a tentative step into troubled waters. Left unanswered are virtually all outstanding questions regarding the who, what, when, where, and why of the transformation of wolves to dogs. Geographically all it does is exclude Central Asia. Whether it does so wrongly may depend on how you define Central Asia geographically.
What makes it bold and radical even is the suggestion that early humans and wolves could have gotten together wherever and whenever they met on the trail of the big game they were following. There are many reasons for that including similar social and familial cultures, but humans and wolves could have joined forces to have become more successful hunters. We learn from Wolves on the Hunt: The Behavior of Wolves Hunting Prey by L. David Mech, Douglas W. Smith, and Daniel R. MacNulty (Chicago, 2016) that while wolves appear excellent at finding and trailing game, they are not very good at making the kill, succeeding perhaps half the time. It is dangerous work at which humans with their weapons excel.
Imagine the scene: Human hunters locate wolves on the hunt by watching ravens who are known to follow them. Human hunters move in for the kill and take as many animals as they can. If smart, they might share immediately with the wolves. If not, the wolves might consume what the humans do not carry off or follow them back to their encampment to take what they can.
The rest is a tale of accommodation through socialization—the ability to bond with another being—and all that entails.
This article originally appeared in Psychology Today's Dog's Best Friend, used with permission.
We may think our dog wIll take a treat from any hand that offers it, but a new study by a team of Japanese researchers suggests that may not be the case. Primates engage in something called “social eavesdropping”— essentially, making judgments about others based on interactions that don’t directly affect their own interests. This study tested dogs’ ability to do the same by setting up situations in which the dogs’ owners asked for help in opening a box and were assisted (helper scenario), rejected (non-helper scenario), or ignored (control scenario) as the dogs looked on. After these interchanges, when the dogs were offered treats, they took them randomly from Helper and Control “strangers” but were biased against non-helpers. According to Kazuo Fujita, professor of comparative cognition at Kyoto university and one of the study’s authors, the ability to socially and emotionally evaluate others “is one of the key factors in building a highly collaborative society.” So, another step in the process of understanding how Canis lupus became familiaris: like humans, dogs are able to pick up clues about who to trust and who to avoid.
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: Studies & Research
Seeing eye to eye
How better to spend a chilly winter afternoon than gazing into a pair of warm canine eyes? As it turns out, there’s a perfectly rational reason to do so, one that also suggests how dogs became our “truest companions.”
In a 2015 study reported in Science (“Oxytocin-gaze Positive Loop and the Coevolution of Human-Dog Bonds”), a team of Japanese researchers led by Miho Nagasawa studied the role oxytocin plays in the ancient relationship between people and dogs. Popularly called the “love” or “cuddle” hormone, oxytocin enhances the attachment between human mothers and infants; the longer the two gaze into one another’s eyes, the greater their levels of oxytocin. The practical effect of this feel-good neurological chemical is to stimulate contact. For mother and child, the shared gaze creates a seamless loop of affection and bonding.
Since both dogs and humans use gaze to communicate, the team hypothesized that this same loop might come into play between our two species. It could also help explain how dogs came to take their place in our lives—or, in science-speak, to suggest a reason for our unique “interspecies affiliation.”
The study’s results seem to confirm the hypothesis. In a series of experimental situations, dogs’ “gazing behavior” increased oxytocin levels in their owners, and when the owners gazed back, the dogs’ oxytocin levels went up as well. And, as with human mothers and infants, the amount of time owners talked to and touched their dogs also increased, thus deepening the bond between them.
So, the next time you find yourself engaged in a mutual-admiration session with your co-pilot, remember: it’s not just a pleasant way to pass the time, it’s also part of nature’s grand plan!
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
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).
* * * * * * *
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.
A romp at the dog park, a run along a trail, a walk around the neighborhood--we know how important it is to get our dogs out and about. But how often do we think about exercising our dog's brain? And really, why should we think about it at all?
Recently, I listened to an online seminar offered by Karen Overall, MA, VMD, PhD, DACVB, CAAB, and board certified Applied Animal Behaviorist, that provided several answers to this question.
Dr. Overall starts out by making the interesting point that it's very likely that dogs co-evolved with humans, which was made easier because both species have similar social systems that rely on work and problem-solving. Dogs still need to problem solve but in today's world, probably don't get enough opportunities to do it, which is why we need to provide them with mental stimulation as well as physical exercise.
She then discusses some of her research and shows videos of dogs working a puzzle box designed specifically for one of her projects; she also analyzes what the dogs' performance indicates about their emotional state.
The takeaway is that stimulating a dog's brain by engaging his capacity to problem solve improves both his physical and mental health. It's also key to helping dogs with behavior problems learn new ways to respond to stress.It's science nerd nirvana, a combination of theory and practical advice (most of which comes at the end in the Q&A segment).
The seminar is titled From Leashes to Neurons: The Importance of Exercising Your Dog's Brain for Optimal Mental and Physical Health, and you'll need to register to listen in (registration is free). Get started here: http://vetvine.com/article/192/akcchf-human-animal-bond-event
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