Good Dog: Studies & Research
People are able to interpret these vocalizations
Research in recent years has shown that our brains can process the emotional content of vocalizations based on acoustic structure, and that various mammalian species share the same brain structures used for such interpretation. That means that we ought to be able to interpret the emotional nature of vocalizations from other species much like we understand those of other people.
Multiple studies of communication across species have found that animals can understand the emotional nature of vocalizations made by members of other species. In a number of studies, experience with the other species enhanced the ability to understand calls from that species.
Cross-species communication is particularly interesting between humans and dogs because of the long history we have of associating with one another, leading to the possibility that we have influenced each other’s vocalizations. In order to investigate people’s ability to understand canine growls, researchers conducted a study in which people listened to recordings of dogs growling and were then asked questions about the emotional state of the dogs.
In the study, “Dog growls express various contextual and affective content for human listeners”, 40 people heard recordings of growling dogs. All of the growls were recording in one of three contexts: guarding food from another dog, playing tug with a person and being approached by a stranger. In the first part of the experiment, the people were asked to rate each growl on a sliding scale for each of the following emotions: fear, aggression, despair, happiness and playfulness.
The emotional profiles based on the 40 ratings of all three contexts were different. Food guarding had the highest aggression rating, followed by the stranger context, and the growls from play had the lowest aggression scores. For the other emotional states, the food guarding and stranger context did not differ from each other, but were rated higher in despair and fear than the playful growls and lower in playfulness and happiness than the growls recorded in play.
In the second test, people were asked in which of those three situations the growl was recorded. Overall, people correctly identified the context of 63% of the growls, which is significantly better than the 33% rate that chance predicts. The play growls were most readily identified, with 81% of them being correctly chosen. The food guarding growls were correctly identified 60% of the time, compared with 50% of the growls directed at strangers. Most of the errors in identifying these two (potentially aggressive) contexts involved confusion between the two of them, rather than with the playful context.
The authors conclude from this study that people can distinguish different types of dog growls, including being able to tell apart growls that are both in potentially aggressive contexts. Previous studies have found that people’s ability to understand canine growls is influenced by the time between growls and the duration of the growls. Based on analysis of the acoustic structure of the growls in this study, the key characters of the growls that make them seem different to people are the rhythm of the series of growls and the length of the individual growls within that sequence. Longer gaps between growls is associated with higher aggression scores. Shorter growls are generally perceived as more positive on emotional scales. In growls recorded in the context of a stranger approaching, the higher the pitch of the growl, the higher the fearfulness score.
Individual people varied in their ability to identify the context of the growls. Overall, women were better at it then men. Also dog guardians outperformed people who do not have dogs. Whether or not a person had ever been bitten by a dog had no effect on whether people were able to determine the context of a growl. This study shows that although people in general can interpret the emotion in canine growls, experience plays a role in how well they are able to do so.
Can tell what your dog’s growls mean?
Wellness: Food & Nutrition
A vet speaks out on genetically modified pet food.
Most dogs now dine on some type of genetically modified (GM) food, often in the form of corn and soy in their kibble. As these ingredients increasingly enter the food supply, we have one more reason to wonder if our shopping choices might be harming our pets.
More animal feeding studies are needed, experts say, and a recent long-term, peer-reviewed report points out why. It found that a diet of GM corn and soy led to higher rates of severe stomach inflammation in pigs, which are physiologically similar to dogs.
Robert Silver, DVM, a Boulder, Colo., holistic vet, tackled the issue earlier this year when he presented his paper, “Genetically Modified Food and Its Impact on Pet Health” at the American Holistic Veterinary Medical Association conference in Kansas City, Mo. Why did he choose this controversial topic, one that few vets even acknowledge?
Silver—a pioneer in the field of holistic veterinary medical practice—says he was inspired by a seminar he attended in Boulder on GM foods and human health. The speakers included Don Huber, a Purdue University professor, and activist Jeffrey Smith, who discussed problems, including reproductive difficulties, that have occurred in livestock fed GM crops.
“I found this seminar mind-opening,” says Silver, the lone vet in attendance. “I had always believed the PR about GM foods—that they are going to feed the world and are a good outcome of our genetic technology.”
The Food and Drug Administration, which regulates the safety of GM crops consumed by humans and animals, considers most GM plants “substantially equivalent” to traditional plants and “generally recognized as safe.” Their regulation involves a voluntary consultation process with the developer before products are brought to market.
Smith, founder of the Institute for Responsible Technology, disagrees. On its website (responsibletechnology.org), he warns that “nearly all GM crops are described as ‘pesticide plants.’ They either tolerate doses of weed killer, such as Roundup, or produce an insecticide called Bt-toxin. In both cases, the added toxin—weed killer or bug killer—is found inside the corn or soybeans we consume.”
Silver says that while “allergies, GI problems, increased risk of cancer, neurodegenerative conditions” and other ills could all be, in part, related to GM foods, “there is no objective evidence of this yet” in dogs. “However, all vets will agree that there has been an uptick in [these diseases] in the past 10 to 20 years.” The advent of GM foods in the 1990s “fits into this timing of disease increases,” he says.
His presentation referred to studies that raise doubt about the safety of biotech crops, such as one reported in 1996 in the New England Journal of Medicine, which found that genes inserted into crops can carry with them allergenic properties.
Silver says that genetic modification introduces foreign proteins that may encourage allergies, and the widely planted Bt corn, which makes its own insecticide, “could possibly cause leaky gut, the gateway to chronic disease.” Corn is a major component of most commercial pet foods. “The big problem with commercial foods is that they are manufactured at high temperatures and pressures,” which alters them and makes them “potentially more allergenic.” And commercial foods contain industrial ingredients that are “more likely to contain GM and herbicide contaminants.”
A study published last year found that GM crops engineered to withstand the toxic herbicide Roundup must now be doused with even more herbicide, since weeds have also developed resistance to it. Residues of these chemicals on crops can find their way into pet food.
A 2013 study published in the science journal Entropy reports that the heavy use of Roundup could be linked to Parkinson’s, autism, infertility and cancers. It goes on to report that residues of Roundup in food can interact with, and enhance, the damaging effects of other environmental toxins. “Negative impact on the body is insidious and manifests slowly over time as inflammation damages cellular systems throughout the body,” the study’s researchers say.
According to Silver, heightened sensitivity to dietary ingredients “is probably what we are seeing with GM foods. It is of concern that this may be driving the increase in GI problems in pets.” Although gluten probably does account for some problems with grain consumption, “I think that grain-free diets, if they are also soy free and contain protein from animals not fed GM crops, can help many dogs, due to being GM free—and not due to some allergy or gluten issue.”
To a holistic doctor, food is medicine, and Silver strongly recommends home meal preparation from individually sourced ingredients to avoid feeding GM ingredients, especially to pets who have other health problems. “I am truly a holistic practitioner in that I believe an ounce of prevention is worth a pound of cure.”
Benbrook, C.M. 2012. Impacts of genetically engineered crops on pesticide use in the U.S.—the first 16 years. Environmental Sciences Europe 24: 24.
Ordlee, J., et al. 1996. Identification of a Brazil-nut allergen in transgenic soybeans. The New England Journal of Medicine 334: 688–692.
Samsel, A., and S. Seneff. 2013. Glyphosate’s suppression of cytochrome P450 enzymes and amino acid biosynthesis by the gut microbiome: Pathways to modern diseases. Entropy 15 (4): 1416–1463.
Good Dog: Studies & Research
Little dogs pee more often on walks
Scent marking is a common form of communication across a wide range of mammals. Although dogs can scent mark in various ways, they most often use urine, which is obvious to anyone who has watched dogs pee here, there and everywhere out on walks or during play time.
Urination, and other forms of scent marking, allow animals to convey a large amount of information in an indirect manner. That means that they can communicate without direct interactions. That has the advantage of avoiding the costs of social interactions, which can include stress, the energetic costs of interacting and potential injury. In many species, body size is closely correlated with competitive ability, which is why scent marking may be especially important to smaller individuals, who may be unlikely to fare well in direct encounters.
Dogs have an enormous size range for a single species, but only recently has the effect of size on frequency of scent marking been investigated. Researchers wondered whether smaller dogs take advantage of the indirect nature of scent marking through urine to be more competitive with larger dogs.
In the recent study, “Scent marking in shelter dogs: Effects of body size”, researchers walked 281 shelter dogs (mostly mixed breeds) that they categorized by size. Small dogs measured 33 cm or less at the withers, large dogs measured 50 cm or more, and medium dogs were above 33 cm but less than 50 cm. They recorded urinations during the first 20 minutes of each walk, noting whether they were directed at a target or not. (Targeted urinations were those that occurred after sniffing a spot on the ground or on some other surface, and those that involved urinating somewhere other than the ground even without sniffing it first.) The study found that smaller dogs marked more often than medium or large dogs and that they were more likely to direct their urine at targets compared to large dogs. Though smaller bladder capacities of smaller dogs could explain increased frequency of urination, that cannot account for the increased frequency of urinating on targets.
As expected, males also marked more frequently and directed their urine at targets more often than female dogs did. The length of time that dogs had spent in the shelter was positively associated with frequency of directed urinations, but not with total number of urinations. Size had no effect on the frequency of defecations on walks, but dogs who had been at the shelter longer were a little bit more likely to defecate on walks.
The authors concluded that smaller dogs use scent marking in the form of urination more frequently that medium or large dogs. It is possible that they are using scent marks in order to avoid direct interactions.
Good Dog: Studies & Research
Scientific study into the cues causing dogs’ reactions
“Fighting like cats and dogs” is an expression that succinctly describes the worst case scenario of dog and cat interactions. Not all dogs and cats have to get along with each other to live full and happy lives, but it sure is important to know which dogs can live with cats and which ones can’t. That’s especially critical for shelters seeking to find homes for dogs, because nobody wants to adopt a dog who will terrorize their cat. Though there are many ways that shelter staff can evaluate a dog’s response to other dogs and to people, there is far less information, and no validated assessment tool, for evaluating how a dog will react to cats. In most cases, we don’t even know what it is about a cat that sets dogs off, other than the useless knowledge that the dog is reacting because the cat is a cat.
A recent study seeks to change that by adding to what we know about which triggers from cats set dogs off. “Dogs’ responses to visual, auditory, and olfactory cat-related cues” concludes that the sound of a cat and how a dog reacts to it may be of critical importance when evaluating dogs. In the study, dogs reacted more to the auditory stimuli of cats than to visual stimuli of cats, but the stimuli they used were not directly comparable.
The visual stimulus was an animatronic children’s toy, the auditory stimulus was a recording of cat vocalizations, and the olfactory stimulus was cat urine. Because only the auditory stimulus was the actual stimulus that a dog would perceive in the presence of a cat, it is hard to accept the conclusions of the study. The actual odor of a cat and the sight of a live cat are different than the stimuli presented in the study.
The researchers found that dogs who had previously hurt a cat were more attentive to the auditory stimuli than other dogs were, though there was no difference in the behavior of dogs in either group towards the visual cat stimulus. The olfactory stimulus was associated with dogs spending more time sniffing than when no olfactory cue was present.
Responses to cat sounds could be a useful predictor of whether or not a dog will get along with cats, but more research is necessary. (It would be of particular importance in future studies to consider the stimuli presented during assessments.) The results of this study could also be explained by concluding that dogs attend more to realistic cat stimuli and that dogs who have previously hurt a cat are especially attentive to realistic cat cues, which in this study only applied to the auditory cue.
Good Dog: Studies & Research
A study of the Delboeuf illusion
Visual illusions reveal the inner working of the eyes and of the brain, and when used in comparative studies, they can teach us a lot about the differences and similarities in vision and neurological processing between species. A common research approach involves using illusions that affect perception of size and investigating whether the illusions affect choice. Allowing research subjects to choose between various options can elucidate the illusions’ effects on members of various species.
One such illusion is the Delboeuf illusion, which causes identically sized objects to appear different in size depending on what surrounds them. In the image below with dark circles of identical size, humans (and other primates) tend to overestimate the size of the circle on the left, which is surrounded by a ring that is smaller than the ring around the circle on the right.
In the study, one set of trials tested whether dogs could correctly choose larger portions of food over smaller ones. Dogs were given a choice between two piles of biscuits on plates—one pile of biscuits weighed 18 grams and the other weighed 32 grams. Once dogs chose to go for one plate, the other one was picked up and no longer available. Sometimes both portions of food were on small plates, and sometimes both were on big plates. Each dog was offered this choice multiple times. Pooling the date into one big analysis, dogs consistently chose the bigger pile of biscuits.
In another series of trials, dogs were offered a choice between equal portions of food that were presented on different size plates. The dogs had to choose between 32 grams of food on a large plate and 32 grams of food on a small plate. If dogs are susceptible to the Delboeuf illusion, the expectation is that they would choose the smaller plate even though the quantity of food was identical on both plates. Instead, dogs’ choices were no different than if they picked a plate at random with no reference to its size. They were not significantly more likely to choose the large plate or the small plate, providing evidence that the Delboeuf illusion does not affect dogs the way that it affects humans. Dogs are not fooled by the size of the plate.
Good Dog: Studies & Research
Studies on dogs following gestures.
AT TWO WEDDINGS, darling ring bearers paraded down the aisle proudly holding the prized objects. They couldn’t have been more than six. When they suddenly stopped—as six-year-olds tend to do—to look at something on the ground, guests leaned into the aisle and pointed toward the beaming faces ahead. Smiles filled the crowd as they continued on their way.
At one wedding, the ring bearer was a little boy, and at the other, a dog.
If we’ve spent any time with companion dogs, we aren’t surprised when a dog stops to check out the ground. It also shouldn’t surprise us that a dog might go where we point. Pointing is about social communication, and it often feels like dogs are right there with us, sometimes even more than members of our own species.
In the last 20 years, dogs’ attention to our communicative gestures—particularly this thing we do with our arm and finger—has attracted enormous attention from researchers around the globe. In fact, the pointing gesture is so fundamental that seemingly no article on the canine mind is complete without a sentence such as “dogs read our gestures, like pointing, more flexibly than any other animal” (New York Times), or—more boldly in Time—“While chimps and even wolves lack an innate ability to understand what pointing means, dogs come by the knowledge naturally.”
These statements tend to produce any number of reactions in dog owners, from “Obviously,” sometimes accompanied with a side of, “Why do they bother to do this research anyway?” to the flip side: “My dog doesn’t do that … what are they talking about?” Or even the more nihilistic view: “Sure they do, but who cares?”
Here’s why we care: this one little gesture, in all its complexity, could be a core feature of the intimate bond we share with dogs.
Since the late 1990s, researchers have tried to uncover why and how dogs pick up on our cues. Initially, key questions focused on whether their ability to follow the pointing gesture arose from our long-standing co-evolutionary history or, alternatively, if they learned the behavior over the course of their individual lives.
Pointing Is About Us
Pointing is something we humans do as part of our social communication, and it is useful only because we all agree on how it should be interpreted. Imagine if your point were perceived as, “Hey! Check out my fingertip. No dirt under my nail. Wonderful, huh?” Not exactly useful for communication. Fortunately, we understand that pointing creates a shared experience beyond our fingertips; pointing draws someone’s attention past our outstretched index finger to something out there in the world.
This cooperative gesture serves us well. Yelling, “Look out!” is only somewhat informative, but yelling, “Look out!” and pointing can help a fellow human locate and respond to a Frisbee sailing in at head level or Godzilla rampaging down Fifth Avenue. Communication achieved.
Despite our mothers’ reminders that pointing is rude, it has a function: it reflects our ability to hold shared attention with others, which could also indicate that someone else is aware of the same thing that we are. Pretty meta. Joint attention can thus be associated with an ability to infer others’ mental states, which is considered an important social capability in humans.
At about six months, children start following the gaze and gestures of others. We start pointing around our first birthday and become increasingly point-savvy as we age. When toddlers see something of interest and point at it, they become excited when we also look. They will also point when seeking something or to provide information (I want that. You dropped something). Regardless of how it’s used or understood at any given age or moment, pointing intrinsically aids our communication with one another.
Do Dogs Get the Point?
It shouldn’t come as a surprise that much of the academic interest in the canine mind that blossomed in the late 1990s was actually largely about us, investigating to what extent dogs responded to our communicative gestures— notably, our pointing. In research labs around the world, it has been a pointing party ever since.
Watch any program covering research into the canine mind and you’re bound to hear mention of studies involving a dog, two cups and a pointing human. The experiment, commonly referred to as the object-choice task, follows some variation of this procedure: a dog first learns he can get a treat for approaching either of two identical cups. He then watches as a person points to one of the cups. Will the dog follow the point to the cup?
Human children are quite good at this task, and numerous studies confirm that dogs are, too. From an early age, dogs are highly responsive to this gesture. Dogs do well when a person points with a foot, or bows or nods. They’ll also respond to what’s commonly referred to as a “momentary” point, in which the person points and then lowers his or her arm before the dog makes a choice. They will follow the point even when a person stands by one cup and points at the other. Although we all know smell is a major player in the canine world, it doesn’t appear to factor greatly into dog performance; when food is hidden under one cup and nobody points, they don’t do so well. Some researchers describe their performance as “remarkable” and “outstandingly flexible.”
Not all species catch our communicative drift. A bee that flies into your car will never be aided by your outstretched arm pointing toward the open window. Given dogs’ long history with us, researchers wondered whether canine sensitivity arose through the domestication process—in which case, wolves, their closest relative, might be less adept in this task—or, on the other hand, whether it’s a product of learning and dogs’ individual life experiences. Or maybe the reality is not so black-and- white. What underlies their highly flexible ability?
Wolves do not follow our gestures as flexibly as dogs. Nor do chimpanzees, our closest relatives. This isn’t to say that wolves (or chimpanzees) can’t or don’t do it. Extensively socialized wolves and enculturated chimps—those highly familiarized with human behavior— can follow our points, but dogs generally respond more readily and easily, and wolves need more exposure to perform similarly. In 2002, Brian Hare of the Duke Canine Cognition Center pulled together then-current research on dogs, wolves and chimpanzees and, in an article in Science, concluded, “Dogs’ social-communicative skills with humans were acquired during the process of domestication.”
Both Nature & Nurture Point to Success
More immediate genetic influences, like artificial selection, could also influence dogs’ skills. Márta Gácsi and colleagues at the Family Dog Project in Budapest found that while all dogs tested followed the point better than chance would predict, dogs bred for cooperative work (like gun dogs) performed better than those bred for independent work (like guard dogs). All the dogs in the study were living as pets and none had received special training, implying that genetics plays a role at some level in enhancing dogs’ ability to follow our gestures.
At the same time, individual life experiences could also contribute to a dog’s responsiveness. For example, the reactions of shelter dogs to our pointing gestures vary widely, and a small group of intensively socialized lab-raised dogs did not fare well in the task.
Lucia Lazarowski of the Comparative Cognition Laboratory at Auburn University, one of the investigators in the lab-raised dog study, saw their challenges first-hand. But when she later adopted Captain, a study participant, and informally examined his responsiveness to pointing, she found he performed much better in her home: “He actually looked in the direction I pointed and sniffed in the area I was pointing to. During the test, however, he was one of the more non-responsive dogs. Now, we like to play a game where I toss small treats around the room for him to hunt, and if he can’t find them, sometimes I’ll point to them, so he probably has picked it up from that.” Captain’s transition to canine pointfollower highlights that learning and life experiences can factor into the skill.
The person behind the point can also affect dog performance. Amy Cook, CDBC, CPDT-KA, conducted a study on the topic at the University of California, Berkeley; reporting in Animal Cognition, Cook noted that when owners and strangers were pitted against one another (in what I hope was described as a “point-off”), dogs tended to follow their owners, even when they received no reward (i.e., the point did not lead to the dog getting food). As Cook explains, “Dogs make decisions by attending preferentially to social signals from humans with whom they have become more familiar.” Many of us think it’s all about us, and our dogs might agree.
If dogs respond to the pointing gesture based on whose finger is doing the work, then again, it looks like life experiences could be controlling the switches. But not so fast: Cook suggests that this unique spin on the issue— dogs being more attentive to a familiar person—could have been shaped by evolutionary pressures to bond with a caretaker. Attachment relationships between dogs and their humans are well documented and, as Cook says, going with your person could be “a successful strategy in the long term.”
Isn’t it nice when everyone can be right? Dog responsiveness to our communicative gestures could be a product of their evolutionary history plus their ability to learn rapidly once in a human environment. In a 2009 article in Behavioural Processes, Pamela Reid, CAAB and vice president of the ASPCA’s Anti-Cruelty Behavior Team, reflects on what’s behind canine responsiveness to our social cues: “Dogs are too skilled for it to be pure trial-and- error learning. Yet it is improbable that a versatile behavior like this would be largely innate.” She suggests that what we see in dogs is an adaptive specialization of learning. “In essence, they come with a built-in head start to learn the significance of people’s gestures, in much the same way that white-crowned sparrows acquire their species-typical song and ducklings imprint on their own kind.” This fits in well with what is understood of instinctual or innate behaviors. As Jack Hailman explained in his inf luential piece in Scientific American in 1969, “How an Instinct Is Learned,” species-specific behaviors require some amount of experience and development.
When Patricia McConnell, CAAB, mulled over the pointing research on her blog, “The Other End of the Leash,” she agreed that dogs could be “predisposed to learn to follow a pointing gesture.” McConnell also highlights something you might have seen yourself: present a very young puppy with an outstretched finger and that puppy is going to approach your fingertip, not follow it to a distant location. McConnell’s point is that point-following in puppies is not automatic, although they learn it very easily.
To this, Reid adds, “Just because a skill appears early in development does not preclude learning. It does, however, demand that puppies be highly attentive to the actions of humans, a tendency that has been confirmed in studies of dog-human attachment.”
What Do You Understand, Dog?
What do dogs think of all this? What does it mean to be a dog who “understands” our pointing gesture?
A 2013 article by Ádám Miklósi and József Topál of the Family Dog Project in Trends in Cognitive Sciences concludes by highlighting that “dog social competence [appears] sometimes ‘infant-like’ or ‘human-like,’ but, importantly, the underlying mental mechanisms may turn out to be quite different.”
It’s hard enough for us to figure out if, for example, our boss is merely suggesting that we do something or telling us to do it. The same is true for dogs and the pointing gesture. Do dogs see pointing as an imperative—“You. Go there.”—or as simply providing information or a helpful suggestion—“I recommend that you go there.”—a subtle yet meaningful difference. A 2011 article published in Applied Animal Behaviour Science by Helene Pettersson and colleagues found that, like children, dogs are more likely to follow a point when it is accompanied by a cooperative tone of voice as opposed to a prohibitive tone. At the same time, dogs sometimes follow the point to an empty container, leading some to wonder whether, under certain circumstances, dogs might perceive the gesture as a command.
Like humans, dogs seem to distinguish when communication is—or is not—intended for them, although they could be relying on a more limited set of cues. Numerous studies find that initiating eye contact and using high-pitched vocalizations help dogs understand that the communication is for them. Setting is also important. In a 2011 study reported in PLoS ONE, Linda Scheider and colleagues found that if a person points to a location where a dog has never experienced reinforcement, the dog is not as likely to follow as he would be if he had previously received reinforcement there (making me wonder whether the ring-bearer dog would spontaneously follow the point to the altar).
At some level, every pointing gesture suffers from a fundamental ambiguity: we might be pointing to a particular object, or we might be pointing to a specific space that happens to be inhabited by a particular object. Usually, we can figure it out without too much cognitive difficulty. Even nine-monthold infants understand when pointing refers to an object as opposed to the place where the object is located.
How about dogs? In a study recently published in the Journal of Comparative Psychology by Tibor Tauzin and colleagues, an experimenter pointed at one of two different toys on either side of him. Before the dog could approach, the experimenter switched the location of the objects in full view of the dog. The researchers wondered whether the dog would approach the object that had initially been pointed at but that was now in a new location, or to the original location of the point. The result? Dogs did not follow the object to its new location. Instead, they approached the old location, which seems to imply that, for the dog, pointing could be more about the location than the pointed-at object.
For those of us who live or work with dogs, much of the value of pointing studies lies in what we do with the results. Despite being unflashy, the pointing gesture is actually rich in dimensions and angles that we can explore with our dogs. As Reid recommends, “Take note of your body gestures. Does your dog attend to your gestures in all cases, or only in certain contexts? Dogs are often way more sensitive than we can grasp. They’re not trying to fool you or trick you, get one over on you or cheat the system. Attending to our gestures is just what dogs do. It’s who they are.”
Cook, A., et al. 2014. My owner right or wrong: the effect of familiarity on the domestic dog’s behavior in a food-choice task. Animal Cognition 17: 461–470.
Franco, F., and G. Butterworth. 1996. Pointing and social awareness: declaring and requesting in the second year. Journal of Child Language 12(2): 307–336.
Gácsi, M., et al. 2009. Effect of selection for cooperation and attention in dogs. Behavioral and Brain Functions 5:31.
Hailman, J.P. 1969. How an Instinct Is Learned. Scientific American 221(6): 98–106.
Hare, B., et al. 2002. The domestication of social cognition in dogs. Science 298(5598): 1634–1636.
Hochman, D. 2014. You’ll Go Far, My Pet. New York Times, April 11.
Kaminski, J., et al. 2011. How dogs know when communication is intended for them. Developmental Science 15: 222–232.
——— and J. Nitzschner. 2013. Do dogs get the point? A review of dog-human communication ability. Learning and Motivation 44(4): 294–302.
Lazarowski, L., and D.C. Dorman. 2015. A comparison of pet and purpose-bred research dog (Canis familiaris) performance on human-guided object-choice tasks. Behavioural Processes 110: 60–67.
Miklósi, A., and J. Topál. 2013. What does it take to become ‘best friends’? Evolutionary changes in canine social competence. Trends in Cognitive Sciences 17(6): 287–294.
Pettersson, H., et al. 2011. Understanding of human communicative motives in domestic dogs. Applied Animal Behaviour Science 133(3-4): 235–245.
Reid, P. 2009. Adapting to the human world: Dog’s responsiveness to our social cues. Behavioural Processes 80(3): 325–333.
Scaife, M., and J.S. Bruner. 1975. The capacity for joint visual attention in the infant. Nature 253: 265–266.
Scheider, L., et al. 2011. Domestic dogs use contextual information and tone of voice when following a human pointing gesture. PLoS ONE 6(7): e21676.
———, et al. 2013. Do domestic dogs interpret pointing as a command? Animal Cognition 16: 361–372.
Tauzin, T., et al. 2015. What or where? The meaning of referential human pointing for dogs (Canis familiaris). Journal of Comparative Psychology 129(4): 334–348.
Udell, M., et al. 2008. Wolves outperform dogs in following human social cues. Animal Behaviour 76: 1767–1773.
Zimmer, C. 2009. The Secrets Inside Your Dog’s Mind. Time, September 21.
Good Dog: Studies & Research
They show a bias against them
In a study called “Third-party social evaluations of humans by monkeys and dogs” scientists evaluated capuchin monkeys and domestic dogs to investigate their responses to people after watching them interact with other people. Specifically, researchers studied their evaluations of people who were either helpful or who refused to help another person. There’s an entire behavioral area of research involving what are called “third-party social evaluations” which simply means the study of how individuals respond to people after watching them interact with others.
In the experiment with dogs, the person pretending (for the sake of science) to be in need of help was the dog’s guardian. The dog watched as the guardian spent about 10 seconds attempting to open a clear container holding a roll of tape. In the “helper” situation, the guardian then turned to one of the people on either side of him/her and held out the container. The helper held the container so that the guardian could open it. The guardian removed the roll of tape, showed it the dog, put in back in and replaced the lid. In the “non-helper” condition, the person who the guardian turned to for help responded to the non-verbal request for assistance by turning away, at which point the guardian continued with the unsuccessful attempts to open it. In both cases, there was a person on the guardian’s other side, who was not asked for help.
At the end of this role-playing situation, both the person who was asked for help and the other person next to the guardian offered the dog treats. When the person had helped the guardian open the container, dogs were equally likely to take the treat from either person. However, when there was a refusal to help, dogs were more likely to choose the treat held by the person who was not asked for help. Dogs chose to avoid taking treats from people who were not helpful. This study found similar results in capuchin monkeys, and the same pattern is well known to occur in children.
It is interesting that dogs act as though they assume that people are okay and trust them—until they have evidence to the contrary. In this study, they gave people the benefit of the doubt, reacting just as well to people who were never asked for help as to those who did provide help. Once they observed someone refuse to help their guardian, though, they avoided taking treats from them. This matches the experience many of us have with dogs in that behaviorally healthy, well-socialized dogs seem to like and trust people in general. It as though dogs pursue a “trust unless specific information advises me to do otherwise” strategy regarding social interactions.
Good Dog: Studies & Research
Humans’ empathy, personality and experience play a role
People understand and react to the facial expressions of dogs in ways that are similar to their responses to people’s expressions. Dogs can distinguish positive human expressions from negative ones, showing that they perceive the emotional content of human expressions. Our mutual understanding of one another is astounding considering that we’re not all that closely related, and yet few humans are surprised by it. We feel a kinship with our canine companions that goes beyond what we share with members of any other species except our own. The biological miracle of our relationship with dogs deserves the attention of scientists, and happily, that is happening more now than ever.
One recent study investigated the role of empathy, personality and experience on people’s ratings of facial expressions. People were asked to rate the expressions (in pictures) of people and dogs showing neutral, threatening or pleasant expressions with regard to each of the basic emotions of happiness, sadness, anger/aggressiveness, surprise, disgust or fear. They also rated how negative or positive the expression was. The study, “Human Empathy, Personality and Experience Affect the Emotion Ratings of Dog and Human Facial Expressions” found that many factors affect how people perceive the expressions of others.
People’s experience plays a smaller role in interpreting facial expressions of dogs than their personality and ability to be empathetic. This suggests that people have a natural, inherent ability to understand the facial expressions of dogs. Perhaps this is because we have co-evolved with dogs over thousands of years, but it may also simply be a result of the similarity of many facial expressions between humans and dogs. We share many of the same muscles and movements as dogs, as do many other mammals, an idea that was made popular in Charles Darwin’s classic work “The Expression of the Emotions in Man and Animals” which was published in 1872. In that book, Darwin made the case that similar behavior in humans and other animals indicated similar internal emotional states, including emotions such as anger, fear, surprise, happiness, disappointment and love. He presented photographic evidence that humans and other animals reveal their emotions through similar facial expressions and behaviors.
Though the role of experience is minimal, it still has an effect on people’s interpretations of canine facial expression. People who were involved in dog-related hobbies such as agility, obedience or hunting, rated happy faces of dogs as “more happy” than people who lack such experience. Experienced people were also more likely to rate neutral expressions as happy, perhaps indicating the subtly of relaxed, content expressions in dogs, or a more positive views of dogs among people who have a lot of experience with them.
Empathy—the ability to understand the emotions and experiences of others—played an especially strong role in the way that people perceived canine expressions. People who are particularly empathetic interpreted the facial expression of dogs more intensely and more quickly than people who are less empathetic. Researchers point out that it is not known whether empathetic people are any more accurate in their assessments of canine expressions.
Personality traits such as being extroverted or being neurotic influenced people’s interpretation of facial expressions. Extroversion influenced ratings of human expressions, but not canine expressions. Neuroticism scores were correlated with lower rankings of anger/aggression in neutral expressions of both species.
The results of this study show that there are many facets to interpreting the emotional expressions of both dogs and humans, and that psychological factors in the observer have an influence. Reading dogs’ facial expressions is a talent and a skill—both natural ability and experience influence people’s reactions to them.
Good Dog: Studies & Research
More satisfaction, less conflict characterize relationship
Long before people began to consider dogs members of the family, many kids were wishing that instead of brothers and sisters, they could just have more dogs. Dogs (and other pets) fulfill all of the roles that researchers consider important in an attachment figure. Kids find them enjoyable, comforting, they miss them when they are not around and they seek them out when they are upset. That may make them especially important for adolescents, who are learning to rely less on their parents and more on relationships with other individuals. The non-judgmental feeling people experience with their dogs may contribute to enhancing young people’s self-esteem.
We know that pets are important to kids, but scientific studies quantifying the value of their relationships are sparse. The recent study “One of the family? Measuring young adolescents' relationships with pets and siblings” demonstrates the true value that kids place on their pets. The research involved surveys of 77 people who were 12 years old. It made some interesting, if hardly surprising conclusions:
If many adults consider their relationships with dogs to be like those they share with children, it’s no wonder that many kids relate to their dogs much like they relate to their brothers and sisters—only better!
Culture: Science & History
Canine Origin Story
Researchers have identified the origin of cattle, horses, pigs, sheep, camels, ducks, chickens, cats and goats. But the genesis of the domestic dog, our oldest companion and the most varied, numerous and widely distributed domestic animal on the globe? We’re still trying to figure out that one.
The study of patterns of diversity is called systematics, and it is a critical subdivision of evolutionary biology. Systematics researchers (earlier called naturalists and taxonomists) sort out species’ genealogical relationships and estimate the points at which populations diverged from one another. Traditionally, they relied on observations of differences in stable physical traits like teeth, skulls and sometimes fossils. More recently, genome-wide comparisons have been used to provide detailed information about species relationships, including the question of when and where wolves became dogs.
Canis lupus familiaris exhibits the most variability in shape, size, behavior and temperament of any mammal species living on earth. About one billion dogs, a population larger than any other domestic subspecies, roam the globe. Canine fossils, some dating to as long ago as 36,000 years, are found on every continent except Antarctica.
Add to that the unusual phenomenon that extreme variation can occur in as little as one generation—a sort of evolution at hyper speed—and we begin to understand why classifying domestic dogs has challenged many of the taxonomical systems that have been used to make sense of Canidae, a family that includes wolves, jackals, foxes and dogs.
Historically, as far back as the fourth century BCE, theories of the descent of animals were the product of using philosophical approaches to relate organic life to the history of time. At first, fundamental ideas about species-change involved sorting out living beings by means of their common essential properties. Philosophers wanted to know how organic life forms were related, not where they came from.
The Greek philosopher Aristotle (384–322 BCE) endorsed the idea that natural beings were always here and always would be. He commented on the dog’s origin, not in respect to the animal’s continuous chronological past but rather, in terms of breed creation. In his view, the dog that nature created was bred to the fox to make small dogs and to bears to make big ones, perhaps making the point that breeds (although he was mistaken about cross-species hybridization) were created by humans. Still, in the Aristotelian view, dogs always existed.
As time went on, the earliest naturalists came to understand that species were related in more complicated ways, and began to devise orderly classification systems. The bigger picture of life, however, was explained within a theological context: a specific act of an omnipotent creator transformed all living things whole and complete. The revolutionary notion that every animal might not be a singular divine creation didn’t materialize until the late Middle Ages, a contradiction that had to be explored hypothetically to avoid conflict with religious doctrine.
In the late 18th century, France’s leading naturalist and the father of paleontology, Georges Cuvier (1769–1832), introduced a new way of looking at life and death. Although he was firmly in the camp of divine creationism, he theorized that animals eventually went extinct.
Earlier, 16th-century English cleric Edward Topsell (1572–1625), author of The History of Four-footed Beasts, whose worldview was defined by fire-and-brimstone religion, based his categories on morality. This was not as much of a stretch as it might seem from today’s vantage point; during Topsell’s time, people had real reason to fear wolves. For them, the predatory wolf and sagacious, noble dog provided excellent examples of two moral extremes.
Domesticated farm livestock had derived from prey species, and no other large predator had (or has) been domesticated. So it seemed illogical that the gentle, devoted dog could have evolved from the wolf. As one writer lamented, “How could such a noble animal as the dog be derived from the likes of the wolf? If evolution were true of dogs and wolves, wouldn’t every beast choose to live the noble life?” Indeed.
But as Darwin later observed, if organic beings didn’t possess an inherent tendency to vary, humans could do nothing. Unlike bears and lions, wolves, for reasons still scientifically unclear, possessed the variation necessary for the creation of the multiple hundreds of dog breeds recognized today.
The Shape of Things
Imagine how frustrating it must have been to try to make sense of how dogs were related and where they came from based on their appearance. Travel the world over and a cat will usually look like a cat, but dogs were a vexing contradiction.
The lack of understanding of the complexity of canine morphology made it difficult to unravel relationships among the ever-increasing numbers of dogs and dog-like animals being discovered on far-away, previously unexplored continents. In the Americas, many were likely Old World breeds introduced by European explorers, eventually returned to a feral state. Over time, they interbred with American Indian dogs, wolves and coyotes, defaulting to pariah-type dogs—a catchall term for semi-feral, free-ranging canines. But a misunderstanding of the distinct differences between wild, tame, domestic and feral dogs added to the confusion about how Canidae should be classified.
The father of modern taxonomy, Carl Linnaeus (1707–1778), assigned dogs both wild and domestic to groups based on their anatomy (muzzle, jaw, ear shape), tail carriage (dog tails curve when relaxed, wolf tails don’t), hair texture, limb length and behavior, criteria that are still used today.
Linnaeus’s contemporary, Georges- Louis Leclerc, Comte de Buffon (1707– 1788)—of whom Linnaeus sniffed, “Always eloquent, often incorrect”— suspected that changes in canine morphology were influenced by environmental pressures, such as climate. But, like his colleagues, Buffon did not consider change within an evolutionary context.
Dividing dogs into categories based on skull shape was Cuvier’s idea, and although his forward-thinking approach to paleontology and the history of organisms would seem to make him an advocate for evolution, he was not. Cuvier’s interest, after all, was in a species’ demise, not its origin. Nevertheless, his contributions greatly influenced Charles Darwin.
Darwin (1809–1882) believed that the dog had multiple origins: from wolves, jackals and at least one South American species. He supported the latter by referencing his observations of dogs in Patagonia who swam underwater and an unusual dog he had seen in Central America. He also advanced the idea of multi-regional domestication.
Darwin further imagined that these small populations of “inferior” native dogs were eventually supplanted by the incursion of more robust dogs introduced by Europeans, an analogy he used to demonstrate the idea of “survival of the fittest.”
Although the fundamental theory of origin is attributed to Darwin, other taxonomists previously proposed similar ideas and connections, including Jean-Baptiste Lamarck and Alfred Russel Wallace. Unlike Lamarck and Wallace, however, Darwin suggested that the evolutionary process occurred through natural selection.
Although Darwin used the breeding of dogs and other artificially selected animals as analogies to explain how natural selection worked, dogs continued to be an untidy group of animals —a puzzle that science has began to unlock by the use of genome-wide sequencing.
In the Genes
Once scientists discovered methods to explore origin at the molecular level, they began to test these historical theories. As early as the 1970s, research papers were published suggesting that dogs may have been derived from several different gray wolf populations, and that canine domestication may have happened much earlier than the fossil record’s 15,000 years ago. By the late 1990s, geneticists worldwide were working together to build a comprehensive map that would chart the evolutionary journey of domestic dogs.
The path was not smooth. Differences of opinion erupted and criticism of research methodologies undermined a delicately balanced collaboration process. Numerous studies argued for canine origin in places as diverse as East Asia, Mongolia, Siberia, Europe and Africa, with timing varying from somewhere between 15,000 and 135,000 years ago. Archeologists who’d studied ancient canine burials were relegated to the sidelines, their fossil records dismissed as “old school,” which created further dissention. Researchers struggled to find common ground, but without much success.
The debate ramped up in 2013, when UCLA evolutionary biologist Robert Wayne and his team published a comprehensive set of data suggesting that dogs evolved from a group of European wolves, now extinct, somewhere between 19,000 and 32,000 years ago.
Two years later, Peter Savolainen, a molecular biologist, and his colleagues at the Royal Institute of Technology in Stockholm published convincing results indicating that dogs originated in China, south of the Yangtze River. They estimated that this dog population split from wolves 33,000 years ago.
Both teams were sequencing DNA. Why were their findings literally all over the map?
Savolainen’s research team analyzed DNA samples from living global dog and wolf populations, then tracked DNA from least to most diverse, going back through time. The general rule is that the older a population of animals, the more diversity it has in its genome, which is a hallmark of ancient origin.
Whether these animals represented the first domesticated dogs or, rather, dogs who migrated to the region from elsewhere and split off from a more ancient dog population, is unresolved. Fossil remains of an ancestral and probably extinct population of wolves that would have been indigenous to the area would seal the deal, but researchers have yet to find them. As Savolainen notes, “We have access to some archaeological samples we are about to analyze. However, there has been quite little archaeological work, especially on animals, in the region.”
While Savolainen and his colleagues worked backward in time, Wayne’s group worked forward, tracking ancient DNA collected from prehistoric bones of wolves and wolf-like dogs, then measuring decreasing genetic diversity. As DNA becomes less diverse, it points to animals transitioning from wolves to dogs. A dead end indicates that a lineage became extinct in that particular region.
Wayne’s team sequenced ancient DNA on canid skulls and bone fragments discovered in present-day Siberia and the Czech Republic dating to between 27,000 and 33,000 years ago. The physical characteristics of the skulls—wider muzzles and foreshortened jaws—suggest that these were ancient proto-dogs, not wolves. The canids may have looked similar to today’s Arctic breeds (for example, the Siberian Husky and the Greenland Dog), but were probably much larger. Although their findings were met with skepticism, the team said their data showed that domestic dogs originated from different wolf populations at different times in different places, in a series of starts and stops. And, they added, living dogs are more closely related to ancient extinct wolves than they are to modern wolves.
In an interesting twist, Wayne’s findings reignited the theory of parallel and multi-regional proto-domestication, an idea that Darwin introduced in the 19th century and one that’s gone in and out of favor since.
Both studies have detractors. Some claim that diversity in Savolainen’s ancient dog population is a result of admixture with European dogs as people traversed the Silk Road. Those who criticize Wayne’s study maintain that he has no solid proof that the ancient bones he’s studying are definitively wolf or dog. Additionally, critics say, his study is geographically biased because he excluded samples from dogs in China based on his position that there are no ancient dogs there.
Although the two studies point in very different directions, Savolainen and Wayne may both be right. It’s possible that dogs were domesticated multiple times in different regions, and that most lineages died out when humans were faced with overwhelming challenges, like climate change. Their findings aren’t mutually exclusive.
Crunching the (Very Big) Numbers
One reason for the disparities, according to Oxford’s visionary evolutionary biologist Greger Larson, who was a part of a team that successfully mapped the origin of the pig, is that scientists studying the dog are not including enough ancient DNA in their studies.
Larson and colleague Keith Dobney, an archaeologist at the University of Aberdeen, had the idea to bring together all the evidence collected to date, find ancient canid specimens from museums, apply state-of-the-art technology and create a database bigger than anything produced before. All they had to do was convince scientists to agree to work together.
Fortunately for canine genetics, Larson was able to sell the idea that more cooperation and collaboration improves the outcome. As chief mediator and conciliator, and supported by substantial funding, he has persuaded more than 50 influential canine evolutionary scientists to join the project. Team members include archaeologists, paleobiologists, anthropologists, zooarchaeologists, paleogeologists and others.
The purpose of the study, which began in 2013 and is slated to wrap up this year, is to combine ancient DNA analysis and geometric morphometric techniques and apply them to archaeological canid remains. This, he suggests, will directly address where, when and how many times dogs were domesticated.
Geometric morphometrics, the study of form in two or three dimensions, is a powerful new way to visually quantify evolutionary relationships. It does this by correlating thousands of geometric points that identify exact places on bones—specifically, points of evolutionary significance that differ between very closely related animals such as the wolf and the dog.
Using a special camera, researchers take hundreds of 360-degree photographs. Software then transfers the pictures to a three-dimensional computerized image that emphasizes a set of tightly defined, very specific points on each bone. The process results in holographic- like images that show domestication in progress through space and time, much like a movie.
Additionally, scientists are isolating and examining ancient DNA collected from museum specimens, looking for changes in the degree of genetic diversity over long periods. This will provide a comprehensive overview of the wolf-to-dog transition from the beginning to the present.
No individual genetic fragment of DNA says This is a wolf or This is a dog. Rather, scientists tease the two apart by looking at strands of DNA and identifying and measuring similarities and differences. As differences become more extreme, the separation between wolf, proto-dog and, finally, dog is suggested.
The team hopes to isolate genetic fragments that can be linked to minor changes in the geometric morphometricimaged samples. Combining the two techniques will tell a deeper, more layered and detailed story about canine domestication.
Larson expects to analyze up to 7,000 specimens representing wolves, incipient canids and domestic dogs. “We’re taking samples from all over the world, sources in not only museums but from private collections, too. Curators are very agreeable when we ask for permission, and they’re usually very happy to have us take photos and DNA samples. They help us, and in turn, we provide more information for their collection.”
While Larson is enthusiastically optimistic about the outcome of this unprecedented project, some scientists not affiliated with the study think the findings will only add to the existing mishmash of conflicting hypotheses. But that’s how science works: come up with an answer and you invariably end up with a lot more questions.
The ongoing search to understand where, when and how many times dogs were domesticated continues to be a topic of active scholarly exploration. Besides the millions of dog lovers who are curious about the roots of our affectionate and unusual cross-species relationship, substantial scientific issues are at stake, issues that may profoundly alter the future of evolutionary theory.
Read about new developments.
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