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
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.
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.
Good Dog: Studies & Research
Puppies are most responsive to this type of talk
Baby talk may make grown-ups sound ridiculous to many people, but that doesn’t take away from its value. Extensive research has shown that human infants are better able to learn language when we talk to them using higher pitches and at a slower speed than when we talk to other adults. This style of communication is called “infant-directed speech”, and it’s natural for many folks to slip into it when addressing young individuals, especially those who are not yet verbal.
A new study called “Dog-directed speech: why do we use it and do dogs pay attention to it?” suggests that the same principle may be operating when humans speak to dogs—another of our social partners who don’t fully understand our language. People tend to talk to their dogs in a way that is similar to the way they address children. There may be value in this “dog-directed speech” as well.
This study investigated the behavior of two species, and reported a major finding about each of them. On the human side, only women were studied, and researchers found that they used dog-directed speech with dogs of all ages, but used higher pitches when they were talking to puppies than when addressing fully grown dogs. For the canines, this worked out well based on their age-related responses to the way we talk to them. Adult dogs were equally responsive to normal speech and dogs-directed speech. Puppies, however, became more engaged when addressed with dog-directed speech than when the women spoke to them as they normally talk. Specifically, it was the higher pitch in the dog-directed speech that influenced how attentive puppies were.
There are many questions that flow naturally from this study and its intriguing results. Do men talk to their dogs with higher-pitched, slower speech patterns, and does the age of the dog influence the degree to which they do it? Do dogs who look more juvenile because of larger eyes, shorter muzzles and bigger heads elicit dog-directed speech more than dogs who have a more mature look? Does dog-directed speech facilitate language learning in dogs as it does in human babies?
Do you talk to your dog using a different speaking style than the one you use for adult humans?
Good Dog: Studies & Research
The same genomic regions affect human social behavior
The remarkable social abilities of dogs include the many ways that they are able to interact with humans. Dogs seek out humans for food, companionship, assistance and information. They have evolved these social skills throughout their recent evolutionary past because of the advantages of communicating and cooperating with people. Genetic changes in the domestic dog over thousands of years are the source of these behavioral changes, but there remains a lot of variation in both canine genetics and canine social behavior.
A recent study (Genomic Regions Associated With Interspecies Communication in Dogs Contain Genes Related to Human Social Disorders) investigated behavioral and genetic variation in hundreds of Beagles with similar upbringing and similar previous experiences with humans. Researchers studied the dogs’ social behavior by presenting them with an impossible task. Dogs were given a container that held three treats, but only two of them were accessible to the dog. The third treat was impossible for the dog to obtain. Using video, researchers quantified the time dogs spent looking at the people in the room with them, approaching them, and being in physical contact with them. Different dogs showed different tendencies to seek human interaction when they faced an unsolvable problem.
To investigate possible genetic sources of this behavioral variation, the scientists used a process called GWAS (Genome-Wide Association Study). Basically, this means that a large number of parts of the entire DNA of each dog were examined to discover potential genetic variants that were associated with the social behavior. This study shows a strong genetic aspect to differences in human-directed social behavior by dogs. Researchers found multiple sections of DNA that were associated with differences in social behavior. In some cases, specific alleles (gene variants) were strongly associated with the tendency to seek out humans for physical contact.
Interestingly, the genes associated with variation in dog behavior in this study have been found to be related to various behavioral issues and social behavior complexes in humans. Specifically, autism, bipolar disorder and aggression in adolescents with ADHD (Attention Deficit and Hyperactivity Disorder) are all variations in human behavior whose genetic contributions come at least in part from the same areas of DNA that influence human-directed social behavior in dogs. This suggests that dogs may be an appropriate and valuable model for studying these aspects of social behavior in people.
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
How to approach future research
“Yes, that’s just how it is with my dog, too!”
“Everybody knew that before reading about it.”
“I figured I wasn’t the only one who felt that way about my dog.”
These are common responses to stories about the many research papers investigating the relationship between people and dogs. Most of us read the latest scientific findings with a great sense of happiness and validation. Our relationship with dogs is very much like our relationship with our children? Yep. Our dogs consider their guardians to be extra special and emotionally important? Whew, thought so. Our attachment to our dogs provides us with many benefits? Duh. Being a helicopter parent does not cause the damage to fur kids that it can to human kids? Yay! Gazing into our dog’s eyes can enhance the feelings of true love between us? Awww.
It’s exciting that there has now been enough research into attachment between people and dogs and the bonds they have for one another to prompt a review paper to suggest where to go from here. The recently published “Measuring dog-owner relationships: Crossing boundaries between animal behaviour and human psychology ” summarizes what we know and discusses what should be studied next as well as how. That means we can all happily anticipate more revelations that will further confirm the many details about what we know: Humans and dogs are close in wonderful ways that benefit us both. In the introduction to the paper, the authors say, “In this review, we propose that the next step in anthrozoology [study of interactions between humans and other animals] research is to use all the potential information within attachment theory, to reveal whether or not different types of relationship styles exist among different dog-owner dyads and how they might be identified. Furthermore, we give suggestions for which factors may contribute to the development of different attachment styles in dogs, hence deserving more attention in future studies of the dog- human relationship.” What this means is that there is a wealth of information about relationships between humans and the styles of connection that people have with one another that can be used to inform future research on the ways that dogs and people forms bonds to one another.
Some suggestions that these authors have are to focus on both dogs and people simultaneously rather than just one side of the relationship. They also recommend investigating physiological as well as behavioral responses to situations (such as separation and reunions) that are often the focus of attachment studies. They encourage addressing both the attachment style of individual dogs and the caregiving style of individual people to help pairs avoid any conflicts that have plagued them in the past and to help them form the best, most positive relationships in the future.
What are you most interested in knowing about the science of your relationship with your dog?
News: Guest Posts
Well, it looks like recent research into prehistoric Japanese graves proves, at least, that dogs were indeed our long-time hunting companions. In this fascinating study written by Angela Perri recently published a fascinating study that proves just this. This line of inquiry started when she was a grad student at Durham University in the UK. As David Grimm writes in Science:
“She wanted to get a sense of how dogs may have aided early humans in taking down game, so she did her best to approximate the activity: In 2011, she joined a group of Japanese businessmen on a wild boar hunt in a dense forest near Hiroshima. ‘It was terrifying,’ says Perri, now a zooarchaeologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. ‘The boar sound like a train. They’re very aggressive, and they have big tusks. At any moment, one could come charging at you.’”
But the biggest takeaway she got was just how impressive the dogs were during this hunt. Not only did the 5 Bloodhounds and Shiba Inus help to track down the prey, but they also warned the humans when the boars were nearby.
That got Perri interested in investigating Japanese research papers for anything about dogs and the Jōmon culture—hunter-gatherers from 16,000 to 2,400 year ago. They lived in the northern islands with a cold climate filled with large terrestrial megafauna of the Pleistocene, like Naumann’s elephants and Yabe’s giant deer. But during the Holocene, 10,000 to 12,000 years ago, there was a climatic warming displacing the larger animals with smaller, quicker ungulates like sika deer and wild boar. As Perri notes in the Antiquity paper, “This environmental shift … led to the creation of new exploitation niches for Jōmon foragers, including important variations in plant availability, coastal resources and terrestrial prey species.”
Perri’s research has involved studying dogs as “hunting technology,” and as she noted, “A hunting partnership between dogs and humans has long been postulated in the archaeological literature, with some researchers suggesting that such a collaborative alliance was the basis for the initial domestication of dogs. She points out that, “Dogs are an important, and in some cases indispensable, hunting aid for many modern forager groups, as they probably were for foragers in prehistory.” And explains that, “Injured deer often run, leading hunters on long chases, and wild boar can be aggressive and quickly learn to evade capture. Hunting dogs mitigate these factors by tracking blood trails, forcing game into vulnerable positions (e.g. in water) and holding prey until the hunter can make the final kill.”
Perri was familiar with the significance that dogs had with many ancient cultures, and how the ethnographic record has confirmed their importance and the revered status many of the dogs obtained, which often was displayed in the manner they were buried in “remarkably human-esque ways, often with grave goods and markers.”
She performed a comprehensive survey of Japanese archaeological literature, and found that the Honshu Jōmon did bury their canine hunting partners in shell middens, same as they did with humans. And found over 110 canine burials from 39 archaeological sites. “They were treating their dogs the same way they treated their human hunters.” And, “Like people, the dogs (which may have resembled Shiba Inus) were placed singly and appear to have been arranged in particular postures. ‘They looked like they curled up and went to sleep,’ Perri notes. Some had suffered what appeared to be hunting injuries—broken legs and teeth—and many of their bones had healed, suggesting people had taken care of them. Some were also found with grave goods, like shell bracelets and deer antlers.” Their ages ranged from newborn to over 12 years old. While the prehistoric puppies weren’t certainly valued as hunters, she noted that “the ethnographic record shows that puppies in hunter-gatherer groups are often valued for their potential as future hunting partners.”
Along with the burials themselves, Perri found that the “importance of hunting dogs in this region is also demonstrated by the numerous dog-shaped clay figures (dogu), including a set that features a dog barking at three wild boar.” Or, “One Yayoi representation of dogs is found on a ceremonial bronze bell (dotaku) depicting a number of scenes, one of which is a boar surrounded by a hunter and a pack of dogs.” As shown here:
A 2500-year-old bronze bell depicting a Jōmon hunt with dogs. Image courtesy of Tokyo National Museum (http://www.tnm.jp/)
Perri concludes that while dogs were an integral part of the ancestral forest hunting culture, once an agricultural subsistence culture took over, the dog burials stopped as well.
As Grimm noted in his article and quotting Melinda Zeder, an archaeozoologist at the Smithsonian Institution National Museum of Natural History, “it may be a disparity in loyalty. “Humans were a bit of a fair-weather friend—we were not as reliable as they were,” she laughs. “We could do to be a little more doglike.” We couldn’t agree with that sentiment more.
Good Dog: Studies & Research
The influence of each species’ feeding ecology
Humans tend to be risk-averse, which is often illustrated by our decision when offered either $100 or the opportunity for a 50-50 shot at receiving either $200 or nothing. In general, humans go for the sure thing. We are not, as a species, risk-prone, or we would gamble on the shot at getting the bigger payoff.
It turns out that a number of studies across a broad range of species have shown that how a species responds to risk is predictable based on their feeding ecology. Animals who depend on erratic, ephemeral food sources, such as meat that they hunt or fruits that are patchy and only ripe for a brief time, tend to be risk-prone. They are willing to gamble on the big payoff. Species that eat diverse types of food or food that is more reliably available, such as vegetation, are risk-averse.
Some of our primate relatives are like us, and some are the opposite. For example, bonobos and lemurs (who both eat a very diverse diet that is mainly vegetarian) are risk-averse like us, choosing a sure thing of lower value over a chance at something better. Chimpanzees and capuchin monkeys—both meat and patchy fruit eaters—are different, being risk-prone and choosing the option that may yield a big reward but could leave then empty-handed. This pattern has appeared in closely-related species birds, too, where those who eat insects are risk-prone, while species who eat seeds are risk-averse.
Scientists haven’t fully explored how widespread this pattern of feeding ecology predicting risk-taking behavior is, but wolves and dogs are an interesting test case. These two species diverged quite recently in an evolutionary sense, but their feeding ecologies differ greatly. Wolves are primarily hunters and dogs are mainly scavengers. Hunting has a high failure rate, but the rewards of a big kill are enormous. In contrast, the source of food for the vast majority of dogs worldwide is human refuse, which tends to be available far more regularly.
In a recent study called “Exploring Differences in Dogs’ and Wolves’ Preference for Risk in a Foraging Task” scientists investigated whether wolves and dogs conform to the pattern seen across so many other species. Based on their different feeding ecologies, they predicted that compared with each other, wolves would be risk-prone and dogs would be risk-averse. The study was done at Wolf Science Centre in Austria, using dogs and wolves who were raised and live at the facility and have had the same overall experiences there.
The subjects of the study were trained to choose either a bowl that contained a dry pellet of food or a bowl that had a fifty percent chance of containing a piece of meat and a fifty percent chance of holding a stone. After each choice, the subject was given the contents of the bowl. All the wolves and dogs in the study were subject to tests to confirm that they understood the choice they were making and also to confirm that they preferred the meat to the dry food pellet.
The researchers found that the pattern of risk-taking seen in other species also applied to wolves and dogs. As expected, wolves were more risk-prone than dogs. However, there is more to this study than that simple conclusion. Wolves learned the system faster than the dogs, and the researchers acknowledge that they may have understood it better than the dogs. Additionally, dogs’ preference for the meat versus dry food pellet was not as strong as it was for wolves. Therefore, the risk of losing out and getting nothing for the chance to get something only a little better than a food pellet may not have been worth it to dogs. There was greater variation among individual dogs in risk-taking strategy compared with wolves, who were more similar in their choices, so it’s possible that there are dogs who are risk-prone as well as dogs who are risk-averse. (Dogs made the risky choice from 38 to 76 percent of the time, while wolves took the risky option 70 to 95 percent of the time.)
Overall, despite the conclusions made from the data in this study, direct comparisons of the choices made by these two species may require further study. It would be very interesting to learn more about decisions to take risks by dogs and wolves in a study with more than seven of each species, though I realize possible subjects for a study such as this are limited. It would also be fascinating to know about the decisions foxes and coyotes would make if presented with the same choices. Comparative research that include dogs as one species among many allow us to learn a great deal about how their evolutionary history and ecology have affected their behavior. It’s one of many ways that we can deepen our understanding of the animals who share our homes and live in our hearts.
Copyright © 1997-2017 The Bark, Inc. Dog Is My Co-Pilot® is a registered trademark of The Bark, Inc