The Nature of Natural

Over the last few years, the sale of dog foods that carry a claim of natural, either embedded into their brand name or proclaimed on their front label, has exploded. According to the marketing research firm Packaged Facts, natural foods are currently the fastest growing segment of the U.S. pet food market. The sale of foods that are marketed in this way doubled between 2008 and 2012 and accounted for almost 80 percent of all new products introduced between January and August of 2014. Natural pet food sales dollars during the same period exceeded 3 billion dollars, making up two-thirds of total pet food sales.

So, what is all of the fuss about? Does a claim of “natural” mean anything for your dog or is it just one more marketing gimmick?

Natural Balance                     Natural dog food label

What natural is: The Association of American Feed Control Officials (AAFCO), the organization that sets pet food ingredient and labeling definitions, states that a pet food manufacturer can include the word natural in a product’s brand name or as a label claim if the food has been preserved using only non-synthetic (i.e. naturally-derived) preservatives. This means that the food cannot include artificially produced compounds such as  butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ), or ethoxyquin. Instead, naturally-derived preservatives such as tocopherols (vitamin E), ascorbic acid (vitamin C), citric acid, and rosemary extract are used. In today’s pet food market, this is not a high bar to clear. Starting in the 1980’s, consumer pressure to eliminate the use of ethoxyquin in pet foods was followed by a general trend away from artificial preservatives. Today almost all pet food manufacturers produce at least one product line of foods that are preserved without synthetic compounds and legally carry the “All Natural” claim.

All Natural

In practice: AAFCO’s definition of “natural” is so broad that it includes nearly every single type of pet food ingredient that is currently included in commercial pet foods, with the exception of chemically synthesized vitamins and minerals. And even with these, there is a loop-hole. A manufacturer that includes these items can still use the natural moniker provided the statement “with added vitamins and minerals” is tacked onto the natural label claim.

What natural is not A pet food label claim of natural does not signify anything about a food’s quality, the source or type of ingredients that it includes, the company’s manufacturing practices, or the food’s safety record. Neither does the appearance of the word natural signify that a food is organic, that it contains no GMO ingredients, is made from human-grade or high quality ingredients, or does not contain by-products. The bottom line is that other than assuring the owner that the food does not contain synthetic preservatives, a label claim of “natural” is meaningless and provides no information that helps to differentiate among foods in terms of their ingredients, quality, digestibility, manufacturing practices or food safety.

Natural vs. organic: There is however an important distinction between the terms natural and organic. According to the USDA’s National Organic Standards Board, a food can be labeled organic if the plant ingredients that are included were grown without pesticides, artificial or sewage sludge fertilizers, or irradiation and exclude genetically modified organisms (GMOs). Animal-source ingredients must come from animals that were raised exclusively on organic feed, were not treated with hormones or antibiotics, and were housed/fed according to an agreed upon welfare standard. However, these requirements were developed for human foods and the National Organic Program (NOP) lacks the legal authority to regulate organic label claims on pet food. Pet food companies can voluntarily choose to meet the NOP standards, apply for NOP certification, and if accepted can use the USDA Organic seal. However, because certification is optional, a pet food company’s use of certified organic ingredients does not mean that the product itself is certified organic via USDA standards. AFFCO has not yet developed a regulation for organic pet foods  and recommends that pet food companies attempt to follow the USDA organic food regulations in their labeling practices. However, companies are not required to do so. If a company chooses to follow the guidelines of the National Organic Program (NOP), you should be able to tell by reading their claim and the ingredients list. If the label states “100 Percent Organic“, every single ingredient must be organic. Foods labeled simply “Organic” must include at least 95 percent organically produced ingredients. Below this level is the label claim “Made with Organic Ingredients”, for which at least 70 percent of the product’s ingredients are organic.

Cat's Poo

Why natural? Oddly enough, despite the fact that the term organic is more narrowly defined and better regulated than the term natural, it is the natural foods segment and not organic pet foods that are taking off in sales. A recent marketing research study examined these differences (1).

The Study: Marketing researchers at New Mexico State University surveyed a group of 661 U.S. dog owners regarding their pet food choices. The researchers used a research methodology called “discrete choice analysis” in which they presented participants with a panel of dog foods that varied in key attributes such as price, ingredient type, label claims, and package size and asked them to identify the food that they would choose for their dog. The objectives of the study were to test the effects of label claims such as “Veterinarian Recommended“, “Natural” and “Organic“, as well as package size, life stage formulation, and price upon dog owner preferences. Because a primary goal was to study perceptions of  natural pet foods, the participants were provided with the AAFCO’s definition of the term natural and the USDA’s definition of the term organic prior to starting the survey.

Results: Of the five primary dog food attributes that were studied, the price of the food was found to be the most important determinant of choice. U.S. dog owners were consistently interested in finding the least expensive food. Following product cost, owners focused most intently upon whether or not the food’s ingredients were promoted as being natural or organic. When these two ingredient types were compared, dog owners were willing to pay the highest (premium) price for a dog food containing a claim of natural ingredients, more so even than for a food stating that it contained organic ingredients. Other attributes such as being recommended by a veterinarian, life stage formulation, and package size were less important. Following price point, the most important driver for choosing a dog food was seeing the word “Natural” somewhere on the label or in the brand name.

Take Away for Dog Folks:  Perhaps the most important fact that dog owners should be aware of is that virtually anything goes when it comes to the “It’s Natural” claim on pet food labels. (This is also true of human foods, by the way). The only significant requirement is that a dog food labels as “All Natural” has is that it cannot contain artificial preservatives. That’s All.

Thats all folks

However, even knowing the ridiculously broad definition of the term natural, people continued to attribute great value to the term and showed that they were willing to pay a premium price to see it on their dog’s food label. In fact, this study showed that owners were willing to pay more for natural ingredients than for organic ingredients despite learning just minutes earlier about the clear differences between the two terms and the stricter guidelines for and regulation of organic foods. Make no doubt about it; this distinction is a win-win for pet food manufacturers because the cost difference between making an “All Natural” pet food claim (that means nothing) and an “Organic” claim that (though optional) is associated with set guidelines for ingredient production and sourcing, is substantial. Expect to see even more of the word natural on pet food shelves in the future.

And train yourself to ignore that word.

Pet food claims for providing superior nutrition, for promoting health, or for being safer do not follow from a claim of naturalness without evidence of such benefit. And, this is especially true when the word means nothing at all in the first place.

Natural Cheetos

Cheetos – Good for you because they contain all natural ingredients

Cited Study:

1. Simonsen JE, Fasenko GM, Lillywhite JM. The value-added dog food market: Do dog owners prefer natural or organic dog foods? Journal of Agricultural Science 2014; 6:86-97.


New Book! “Beware the Straw Man: The Science Dog Explores Dog Training Fact & Fiction”

Beware the Straw Man: The Science Dog Explores Dog Training Fact & Fiction” is now available! Click on the image below for more information and to order.

Book summary:   The Science Dog (aka Linda Case) takes a skeptic’s look at many commonly held beliefs about dog behavior and training. Each of the book’s 32 essays explores a question posed by leading researchers and provides detailed and thought-provoking analysis of their findings. Learn how dogs react to different training methods, discover the pitfalls associated with the use of extinction, and read about new studies that evaluate programs that communities use to keep children safe from dog bites. Other essays explore owners’ ability to understand their dog’s emotions, how people perceive and train small dogs, and if standard behavior tests used by animal shelters to assess dogs’ adoptability hold up under scrutiny. Whether you are a professional trainer, work with dogs in shelters or rescue groups, own a dog-related business or train your dog for fun, the information provided in “Beware the Straw Man” will be of interest and of value to you. Be forewarned though; this book does not provide the reader with pat answers. Rather it presents the current state of the science of dog training and encourages you to decide for yourself how to proceed.

                                                                             ♥♥♥♥♥♥♥♥♥♥♥♥♥♥Beware Straw Man Cover

Not Your Grandmother’s Kibble

When I was in graduate school, a fellow student recommended a book called The Structure of Scientific Revolutions by Thomas Kuhn. Published in 1962, it was already considered a classic in the philosophy of science by the 1980’s. Kuhn is responsible for defining and popularizing the concept of “paradigm shifts.” He explains that historically, scientific advancement has occurred as a series of relatively uneventful periods punctuated by intellectually abrupt “revolutions.” These are discoveries that are so new and unexpected that they change the entire way in which we do science, think about a topic, or even live our lives. Once accepted, these new concepts completely replace those that preceded them.

Kuhn CycleParadigm Shifts: A paradigm shift is a change from one way of thinking to another; a new way of looking at an old problem. These shifts do not just happen, but rather are driven by people of great minds or by events of great import. For example, the development of agriculture changed humans from nomadic hunter-gatherers to sedentary community builders, and for better or for worse, allowed us to populate and dominate the entire planet. Similarly, Darwin’s theory of evolution changed not only how we looked at all other species on the planet, but (with some continuing resistance) how we look upon being human itself. Paradigm shifts also can be caused by new inventions. The invention of the printing press in the 1400’s led to the unprecedented preservation and distribution of knowledge and had a major role in the scientific revolution. In our own time, the introduction of the personal computer and the internet have had cultural ramifications that have impacted our personal and professional lives in ways that could never have been anticipated. These transformations all involve a replacement of old belief systems or way of doing things with an entirely new paradigm.

At the risk of over-dramatization, it appears that we are in the middle of a paradigm shift today that affects how we think about commercial pet foods and how best to feed our dogs. Although not a life-changing event for most people, or even perhaps not for most dog people, the changes that we are seeing in the pet food industry and among owner attitudes during the last seven years are unprecedented and certainly worth examining.

Paradigm Shift

If you remember, the pet food industry was literally “born” in the early 1960’s as a consequence of the development of the extrusion process. Producing dry foods that provided complete nutrition, stored well and were convenient allowed dog owners to feed their dogs a single product for a relatively low price and to feel good while doing it.

Vintage Label

Pet Food Choice Explodes: Starting in the mid 1980’s, research that studied the nutrient needs of dogs increased dramatically both at universities and within the private sector (pet food companies). This expansion occurred in large part because of the increasing importance that dogs had to our lives and the creation of an entire pet industry around that relationship. The advances in our understanding of canine nutrient needs and feeding behavior led to improvements in both the quality of many foods as well as an explosion in the number of brands and products that were available to dog owners.

By the new millennium, more than 90 percent of Americans were feeding a commercial dry (extruded) dog food to their dog and the explosion of life stage and life style foods has occurred almost exclusively within the extruded dry product segment. In addition to puppy and adult foods, we saw the development of products that target different adult sizes, activity levels, breeds, and health conditions. The variety of ingredients included in foods has similarly expanded, with the inclusion of new protein sources, grains (or no grains), types of fat and “functional” nutrients.

Cat's Poo

On the business side of things, the 1990’s and early 2000’s witnessed unprecedented growth in sales, followed by an epidemic of pet food company mergers and acquisitions. Small, privately owned pet food companies and their brands were gobbled up by a small handful of multi-national corporations. Over time, a single company became the owner not only of multiple brands of food but also numerous product lines within brands. By the early 2000’s, the majority of pet food brands sold in the United States were owned by the “five giants” of the pet food industry: Mars Petcare; Nestle-Purina PetCare; Colgate-Palmolive (owner of Hills); Procter and Gamble (P&G) Pet Care; and Del Monte Foods (recently renamed Big Heart). These five are now further consolidated down to four, when Mars purchased all of P&G’s pet food brands (Eukanuba, Iams and Natura) in April of 2014.

Pet Food Recall of 2007: The pet food paradigm shift that began in the early 2000’s accelerated tremendously in the spring of 2007. Sadly, this change came about not in response to a new discovery or an innovative type of pet food. Rather, it was set off by a massive pet food recall of unprecedented proportion that was caused by the intentional adulteration of a common food ingredient.  The problem began when numerous dogs and cats started to become suddenly ill with renal failure, many never recovering. Although we now know that the company that was responsible, Menu Foods, had started to investigate the problem by early March, it took weeks of consumer complaints before a voluntary recall was initiated.

Worst nightmare: I remember that time well. My mom and I were attending a Canine Freestyle seminar together in St. Louis, Missouri. My mother, a trainer also, had been a board member of NADOI, and this seminar was held in conjunction with the organization’s annual meeting. During a seminar break, a long-time friend of my mother’s came and sat with us. She tearfully related that she had lost her beloved, young, German Shepherd earlier that week to renal disease, brought on by the tainted food. The most heart wrenching detail that I remember from that conversation was the distraught woman telling us of her continued attempts to entice her sick dog to eat the tainted food prior to knowing that it was the food that was actually causing her dog’s illness and eventual death. She spoke of warming the food and adding little tidbits to it, in an attempt to nurture her boy back to health. For me, and also for my mom and others in the room, this put a highly personal face on the daily statistics of pet illness and loss that we were reading about in the media. It is an understatement to say that losing a dog in such a way is every dog lover’s worst nightmare.

Over the following months and into early summer, the extent of the problem became appallingly evident. According to Dr. Stephen Sundlof, who was the head of the FDA’s Center of Veterinary Medicine at the time, the root cause of the contamination came from a switch in ingredient supplier. Buyers at Menu Foods had recently changed to a new supplier of wheat gluten, an ingredient that is included in canned foods as a thickening and binding agent. They had switched to an Arizona-based company called ChemNutra that was importing the ingredient from China. ChemNutra offered wheat gluten at a price that was about 30 percent lower than the cost of making (not selling) the ingredient in the US. It eventually became known that the Chinese suppliers were intentionally adding two non-food compounds, melamine and cyanuric acid, to wheat flour in order to make the flour appear to be the more expensive ingredient, wheat gluten. The adulteration had the effect of raising apparent protein levels of the ingredient in a deceptive manner, thus allowing the company to charge a higher price for what was actually a very low quality product. When present together in a pet food, we now know that melamine and cyanuric acid crystallize into a complex that accumulates in the kidney, leading to kidney damage and death. By the end of the disaster, it was estimated that over 5,000 pet food products had been tainted and were recalled and thousands of cats and dogs were sickened or killed.

This event, along with several subsequent pet food recalls for salmonella and aflatoxin (a toxin produced as a result of mold contamination to corn or wheat ingredients), led to changes in dog owners’ understanding of how pet food was made in the United States and to a dramatic shift in overall perceptions of the pet food industry. Perhaps the biggest shock to dog owners was the revelation that a single manufacturer, in this case Menu Foods Limited, was responsible for the production of dozens of brands of pet food that were owned by a wide variety of pet food companies, including the “big five” discussed earlier. As a result, different brands of foods were often produced using the same ingredients that originated from a common supplier. Perhaps even more significant was the realization that many pet food ingredients were sourced from outside of the United States, often in countries such as China, that had few or insufficient regulatory standards. Collectively, the truths that were revealed in the wake of the largest and most devastating pet food recall in history led to a rapid loss of consumer confidence and to increased skepticism of pet food companies and their products. Contaminated food

Other cultural shifts: While pet food recalls are dramatic and highly salient examples, several other cultural changes have also contributed to the pet food paradigm shift. It is common knowledge among people who work in the pet food industry that trends occurring in the human food industry quite reliably predict what we can expect to see occurring a few years later in the pet food industry. A recent example of this is the increased popularity of grain-free dog foods. These foods have their origins in the gluten-free and eventually grain-free movement in human diets. Grain-free brands of dog food were virtually non-existent before the year 2000. Today, almost every pet food company includes a dedicated grain-free brand or product line and some companies sell nothing but grain-free products. Similarly, as interest has grown about where and how our own food is produced, so too has there been increased interest in knowing more about the origin of the foods that we feed to our dogs and cats. Owners are increasingly sophisticated in their knowledge of foods and are more willing than ever before to scrutinize ingredients and label claims. Market segments that were once considered small and “niche” are now mainstream. Some owners wish to choose only foods that include organic ingredients, some eschew any foods that may contain genetically modified organisms, and others are switching to raw diets for their dogs. Many are concerned about the source of ingredients that go into foods as well as about who is producing their dog’s food. And, some are equally concerned with the environmental or animal welfare issues surrounding their own and their dogs’ foods or with consuming only foods that originate locally or regionally.

Not just your grandmother’s kibble anymore: So, let’s take a look at where exactly the pet food paradigm shift has led us. During the last 5 years, the pet food industry has witnessed an explosion of innovation and the development of new feeding philosophies and products. The development of extrusion in the early 1960’s almost instantaneously revolutionized the pet food industry, in large part because it led to the mass production of foods that were convenient, economical and that could be stored for long periods. Because the extrusion cooking process efficiently cooked starch and resulted in both increased digestibility and enhanced taste, dry foods contained a relatively high proportion of starch, plus various sources of animal- and/or plant-based proteins, animal or plant fats/oils, and vitamin/mineral “pre-mixes.” Convenience has been an attractive feature of extruded dry foods for many dog owners. Not only are these foods easy to store and feed, but they can now be purchased at every supermarket and big box outlet found in America’s shopping centers. Owners can purchase dry dog foods at grocery stores and mass market retailers such as Walmart, Target and even Walgreens. Together, these large retail sources are responsible for more than 70 percent of dog food sales. The pet superstores are responsible for about one-fifth of sales, followed distantly by small pet supply stores. Generally speaking, the perception of owners is that higher quality (i.e., premium) foods are available at pet supply stores, while the lower quality brands, which are also lower in cost, can be readily purchased at grocery store chains and mass market retailers. And generally speaking, these distinctions are true.

Notwithstanding the continued popularity of extruded foods, there are a number of completely new approaches to producing dog foods that have been developed in recent years as part of this paradigm shift and that provide a new set of choices to dog owners. Several of these approaches are used primarily to produce safe and storable raw foods, such as dehydration and freeze-drying. Others are a new approach to cooking and storing foods that contain ingredients other than those that are typically included in dry foods, in some cases, using ingredients that never leave the “edible” (USDA term for human grade foods) supply stream and so are classified as being produced from human grade ingredients and using human food production methods. While these foods still comprise a relatively small portion of the pet food market, I think they reflect the enhanced innovation and exploration into new possibilities that are coming about during the new age of pet foods as well as a response from dog owners who are demanding higher transparency from the pet food industry, along with higher quality and safer foods. The table below summarizes several of these approaches and provides a few brand examples for you to explore, should you so choose. (Note: The table does not contain a complete list of brands, but rather is intended to provide a randomly selected group of brands as examples).

Food Form Description Brand Examples
Dehydrated Dehydration involves removing most of the water from the mixed and ground raw ingredients. Gentle heating during dehydration kills microorganisms and partially cooks the food. Portions are rehydrated with warm water immediately prior to feeding. The Honest Kitchen, Addiction, ZiWi Peak
Freeze-dried Ingredients are mixed and then frozen under a vacuum to allow which allows product moisture to sublimate directly from the solid phase to the gas phase. Portions are rehydrated with warm water. Stella & Chewy’s, Nutrisca, Orijen, SoJo
Refrigerated Ingredients are gently cooked (not extruded), shaped into tubes or patties and refrigerated. FreshPet
Frozen (Cooked) Ingredients are gently cooked (not extruded), then frozen. May be complete and balanced or a pre-mix to which other ingredients are added at home Evermore, Bil-Jac, Buddy’s Kitchen
Frozen (Raw) Ingredients are combined, frozen, and packaged as rolls, or individual meal-size patties Stella & Chewys, Nature’s Variety, Bravo!
Pre-mixes A frozen or freeze-dried mix of either non-meat ingredients (to which the owner adds cooked or raw meat), or of meat ingredients (to which the owner adds vegetables, fruits, grains) Fresh Oasis, SoJo, Bravo!
Raw Coated Baked or extruded kibbles coated with freeze-dried (usually raw) ingredients Great Life, Instinct (treats)

 NOTE: This essay was excerpted from my 2014 book “Dog Food Logic(Dogwise Publishing, 2014), Chapter 7, pages 116-119. To continue reading and learn more, just click the image below. (Also available on Amazon). This essay kicks off a new series of Science Dog blogs that will examine new research in canine nutrition and feeding. Coming Soon – “The Nature of Natural”!

Amazon Cover

Talking Turkey

I grew up with a story-book grandmother. She was my mother’s mom, “Nana” to my sister and me. As required of all perfect grandmothers, Nana was a great cook and regularly expressed her love through sumptuous meals and comfort foods. Although she did not actually reside “over the valley and through the woods”, her home was definitely the place to be on all food-oriented holidays, including birthdays (cake!), Christmas (cookies!), and of course, the ultimate All-American food holiday, Thanksgiving (turkey!). Like many Americans on this day, my family gorged ourselves with all that Nana placed on her over-loaded dining room table – mashed potatoes, stuffing, butternut squash, warm rolls, salads, corn casserole, and of course, the mandatory roasted turkey. Following this annual feast, my sister and I would fall into food-induced stupors, sleeping off our over-indulgence for several hours before rousting ourselves to eat one more piece of pie.

Tgiving Food Coma


A number of years later I learned that my post-feast drowsiness was (presumed to be) caused by to a specific nutrient in turkey. This theory, first put forth by a nutritionist, proposed that turkey meat contains unusually high levels of the amino acid, tryptophan. Once absorbed, tryptophan is used by the body to produce serotonin (a neurotransmitter) and melatonin (a hormone). The neurological pathway through which serotonin works has anti-anxiety and calming effects and melatonin helps to induce feelings of drowsiness (i.e. enhances sleep). Therefore, the theory goes, after consuming a high-protein meal, in particular one that is high in tryptophan, the body’s production of melatonin and serotonin increase, which in turn cause drowsiness, reduced anxiety and a calm state of mind. Presto – the post-turkey coma!

Tryptophan Cartoon

Tryptophan Takes Off: The tryptophan/turkey theory became so popular and widespread in the early 1980’s that nutrient supplement companies decided to by-pass the turkey part of the equation altogether and began producing and selling tryptophan supplements (L-tryptophan). These were initially promoted as sleep aids and to reduce signs of anxiety. However, as is the nature of these things, the promoted benefits of L-tryptophan rapidly expanded to include, among other things, claims that it would enhance athletic performance, cure facial pain, prevent premenstrual syndrome, and enhance attention in children with attention deficit-hyperactivity disorder. (My personal favorite was the promotion of L-tryptophan as a treatment for Tourette’s syndrome). L-tryptophan enjoyed a robust reputation as the nutrient for “all that ails ye’” until 1989, when it was found to be responsible for causing eosinophilia-myalgia in more than 5000 people, killing at least 37 and permanently disabling hundreds. The US Food and Drug Administration quickly banned its import and sale as a supplement. Although the problem was eventually traced to a contaminant in a supplement that was imported from a Japanese supply company (and not the L-tryptophan itself), the ban remained in effect until 2009. Today, L-tryptophan is once again available as a nutrient supplement but it has never regained its earlier popularity in the human supplements world.

What About Dogs? Given its history, it is odd that L-tryptophan was largely ignored by the dog world until a research paper published in 2000 suggested that feeding supplemental L-tryptophan might reduce dominance-related or territorial aggression in dogs (1).The researchers also studied dogs with problem excitability and hyperactivity, but found no effect of L-tryptophan on either of these behaviors. However, the paper led to the belief that tryptophan supplementation was an effective calming aid in dogs (which it definitely did not show in the study) and as an aid in reducing problem aggression. Today, a range of L-tryptophan supplements are marketed for reducing anxiety and inducing calmness in dogs. Interestingly, none are pure L-tryptophan, but rather also include other agents that are purported to have a calming effect on dogs, such as chamomile flower, passion flower, valerian root, or ginger.

What Does the Science Say? Does eating turkey or taking an L-tryptophan supplement reduce anxiety and induce calmness? And, can it be used as an effective nutrient supplement to reduce anxiety-related problem behaviors in dogs?

 The Turkey Myth: It is a myth that consuming turkey induces drowsiness or reduces anxiety. The theory fails on several counts. First, turkey meat does not actually contain a uniquely high level of tryptophan. The amount of tryptophan it contains is similar to that found in other meats and is only half of the concentration found in some plant-source proteins, such as soy. (Do you get sleepy after gorging on tofu?).

Trypt Levels in Foods


Second, researchers have shown that the amount of tryptophan that is consumed after a normal high-protein meal, even one that contains a lot of tryptophan, does not come close to being high enough to cause significant changes in serotonin levels in the blood or in the synapses of neurons, where it matters the most. Third, to be converted into serotonin (and eventually into melatonin) tryptophan that is carried in the bloodstream following a meal must cross the blood-brain barrier and enter the brain. This barrier is quite selective and only accepts a certain number of amino acids of each type. Tryptophan is a very large molecule and competes with several other similar types of amino acids to make it across the barrier. Following a meal, especially if the meal is high in protein, tryptophan does increase in the blood and is pounding at the blood-barrier door for access. However, it is also competing with other amino acids that are also at high levels (turkey contains all of ‘em). As a result, very limited amounts of tryptophan make it into the brain for conversion following a meal that includes lots of other nutrients.

        Why So Sleepy? The real explanation for the drowsiness and euphoria that we all feel following a great turkey dinner at Nana’s house is more likely to be caused by simply eating too much (which leads to reduced blood flow and oxygen to the brain as your body diverts resources to the mighty job at hand of digestion), imbibing in a bit of holiday (alcoholic) cheer, and possibly, eating a lot of high-carbohydrate foods such as potatoes, yams, and breads, which lead to a relatively wider fluctuation in circulating insulin levels. Whatever the cause, don’t blame the turkey or the tryptophan.

Eat too much  Blame Tryptophan                                        THE TRUE CAUSES OF TURKEY COMA

Tryptophan Flying Solo:  The erroneous focus upon turkey did have some positive consequences in that it led to a closer look at tryptophan’s potential impact upon mental states and behavior when provided as a supplement. As a serotonin precursor, tryptophan (and its metabolite 5-hydroxytryptophan or 5-HTP) has been studied as either a replacement or an adjunct therapy for serotonin reuptake inhibitors (SRRIs), medications that are commonly used to treat depression in people and are sometimes prescribed as treatment for anxiety-related behaviors in dogs. Although limited work has been conducted regarding the effects of tryptophan supplementation in dogs, several informative papers did follow the initial dog study of 2000:

            Tryptophan and anxiety: Researchers at Wageningen University in the Netherlands studied a group of 138 privately owned dogs with anxiety-related behavior problems (2). Study design: Half of the dogs were fed a standard dog food (control) and half were fed the same food, formulated to contain supplemental L-tryptophan. Neither the owners nor the researchers were privy to dogs’ assigned groups. In other words, this was a “double-blind, placebo-controlled study” (see my book “Dog Food Logic” for more about studies), the Gold Standard of research designs. Dogs were fed their assigned diet for 8 weeks, during which time the owners recorded behavior changes. At the end of the study, the researchers also performed a set of behavior evaluations to assess the dogs. Results: Although blood tryptophan levels increased significantly (by 37 %) in the dogs that were fed supplemental tryptophan, neither the owners nor the researchers observed any difference in behavior between the supplemented group of dogs and the control dogs. There were moderate changes in behavior over time in all of the dogs, but this change was attributed to a placebo effect. Overall, supplementation with L-tryptophan demonstrated no anxiety-reducing effects in the dogs enrolled in this study.

        Tryptophan and abnormal-repetitive behaviors: This was another double-blind and placebo-controlled study (3). In addition, the researchers used a “cross-over” design in which half of the dogs are first fed the control and the other half are first fed the test diet for a period of time and are then all switched to the alternate diet for a second study period. This is a well-accepted study design that is helpful when a researcher has limited number of subjects and that helps to control for the placebo effect. A group of 29 dogs was identified, each presenting with a form of abnormal-repetitive behavior. These were: circling, anxiety-related lick granuloma, light chasing/shadow staring, or stool eating. (Note: One might question the inclusion of stool-eating in this study, since many pet professionals consider eating feces to be a form of scavenging behavior that is normal and common in the domestic dog). Dogs were treated for 2-week periods and the frequencies of their abnormal behaviors were recorded daily. Results: The researchers reported no effect of supplemental L-tryptophan on the frequency or intensity of abnormal-repetitive behaviors. Although the owners reported slight improvements over time, this occurred both when dogs were receiving the supplemental tryptophan and while they were eating the control diet (there is the insidious placebo effect again). Limitations of this study were that it was very short-term and it targeted uncommon behavior problems that are notoriously resistant to treatment. Still, this study did not provide any evidence to support a use of tryptophan supplementation for repetitive behavior problems in dogs. (So, to all you folks who live with poop-eaters – sorry, no easy answer here with L-tryptophan).

          Tryptophan-enhanced diet and anxiety: Dogs with anxiety-related behavior problems were fed either a control food or the same food supplemented with L-tryptophan plus alpha-casozepine, a small peptide that originates from milk protein (4). This was a single-blind, cross-over study in which only dog owners were blinded to treatments. All of the dogs were first fed the control diet for 8 weeks and were all then switched to the test diet for a second 8-week period. Because the treatment group always followed the control in this study design, it is impossible to distinguish between a placebo effect and an actual diet effect in this study. (Note: This is a serious research design flaw that the study authors mention only briefly). Results: A small reduction in owner-scored anxiety-related behaviors was found for four of the five identified anxiety problems. However, in all of the cases, initial severity of the problems were rated as very low (~1 to 1.5 on a five-point scale in which a score of 0 denoted an absence of the problem and a score of 5 denoted its highest severity), and the change in score was numerically very small, though statistically significant. This is not surprising since there is not very much wiggle room between a score of 1 and a score of 0. Finally, given that the food was supplemented with both L-tryptophan and casozepine, conclusions cannot be made specifically about L-tryptophan.

Take-Away for Dog Folks

First, forget the turkey. While it can be a high-quality meat to feed to dogs (especially if you are selecting a food that includes human-grade meats or are cooking fresh for your dog), as a protein source turkey contains no more tryptophan than any other dietary protein. Feeding turkey to your dog will not promote calmness (unless of course, you allow him to stuff himself silly along with the rest of the family on Thanksgiving Day). Second, keep your skeptic cap firmly in place when considering the effectiveness of supplemental L-tryptophan or a tryptophan-enriched food as a treatment for anxiety-related problems. The early study in 2000 reported a modest effect in dogs with dominance-related aggression or territorial behaviors but found no effect in treating hyperactivity. Subsequently, two placebo-controlled studies reported no effect at all and the single study that reported a small degree of behavior change could not discount the possibility of a placebo effect.

Human nature encourages us to gravitate toward easy fixes for things that ail our dogs. Hearing about a nutrient supplement or a specially formulated food that proclaims to reduce anxiety and calm fearful dogs is powerful stuff for dog owners who are desperate to help their dogs. These types of claims are especially appealing because anxiety problems can have a terrible impact on a dog’s quality of life and are often challenging to treat using the standard (and proven) approach of behavior modification. An additional risk that must be mentioned regarding our inclination to gravitate toward unverified nutritional “cures” is that well-established approaches such as behavior modification may be postponed or rejected by an owner who instead opts for the supplement, wasting precious time that could actually help a dog in need. Until we have stronger scientific evidence that demonstrates a role for L-tryptophan in changing problem behavior in our dogs, my recommendation is to enjoy the turkey, but train the dog.

Cited References:

  1.  DeNapoli JS, Dodman NH, Shuster L, et al. Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression, and hyperactivity in dogs. J Amer Vet Med Assoc 2000; 217:504-508
  2. Bosch G, Beerda B, Beynen AC, et al. Dietary tryptophan supplementation in privately owned mildly anxious dogs. Appl Anim Behav Sci2009; 121:197-205
  3. Kaulfuss P, Hintze S, Wurbel H. Effect of tryptophan as a dietary supplement on dogs with abnormal-repetitive behaviours. Abstract. J Vet Behav 2009; 4:97.
  4. Kato M, Miyaji K, Ohtani N, Ohta M. Effects of prescription diet on dealing with stressful situations and performance of anxiety-related behaviors in privately owned anxious dogs. J Vet Behav 2012;7:21-26.

*A version of this article was published in the July 2014 issue of Whole Dog Journal.

You Barkin’ At Me?

I have a ring tone on my mobile phone that I really like. It barks. Five barks (bark-bark-bark-bark-bark) for each ring. It is a real dog’s voice, not a person fake-barking in that annoying way that certain people feel compelled to do when they see a dog. (Really, what is that about anyway?). Earlier this week, my phone started barking while I was getting my hair cut. My hairdresser laughed and asked if any of my  dogs react to the barking phone. I told him that no, they always ignore it, which is strange, since it is definitely the recording of a real dog bark.

To which he replied “Maybe the dog isn’t saying anything”.

Barking Cartoon

Maybe. But recent research suggests that dogs do have something to say and that other dogs are often quite interested in hearing what that is.

Background information: The auditory (vocal) signals that animals make often have important communication functions and possess context-specific information. This means that a sound may be conveying information about several things at once. For example, an alarm call may vary in subtle but detectable ways depending on the location of the threat and how dangerous it is. Vocalizations may also be important signals that allow animals to recognize and identify one another. Indeed, this ability has been demonstrated in a wide range of species of birds, mammals, and even amphibians.

So, what about dogs? Previous research has shown that like many other animals, the sounds that dogs make are varied and highly context-specific and that humans, especially those who are experienced with dogs, are quite capable of distinguishing between different types of dog barks (1,2). However, while it is easy to test a human’s response to dog barks (we can just ask them questions), it is more difficult to ask dogs what they are learning when they listen to the vocalizations of other dogs.


Difficult, but not impossible. A group of ethologists at the Eotvos Lorand University in Hungary recently designed two clever experiments in which they were able to ask dogs – What are other dogs saying to you when they bark?

The technique: The reseachers used an approach called “habituation-dishabituation” to measure dogs’ reactions to the recorded sounds of barking.  The technique works like this. The dogs were first allowed to habituate to recordings of a particular dog who was barking in a particular situation. Habituation was measured by recording the number of seconds that the listening dog continued to show interest in a dog/situation combination over time. A decrease in attention was interpreted to indicate habituation. A dog would stop reacting to the sound as it lost significance much in the way we habituate to the sound of our air conditioner kicking on because it is heard repeatedly through the day.  Then (here is the clever part), the researchers changed either the identity of the dog who was barking or the context of the bark. The introduction of something that is new or unexpected should cause dishabituation, but only if the listener notices the change. (For example, if your air conditioner suddenly started making a rattling noise, you would dishabituate to it and take notice, right?).  In this case, if the listening dog responded by suddenly increasing his/her attention to the recording, this means that the dog noticed the change and so was capable of distinguishing between different dogs and/or different causes of barking. If on the other hand, the change did not cause a change in the listener dog’s behavior, such a result would indicate that the dog had habituated to the general sounds of a dog barking and was not gleaning any specific information from the recordings. The group of investigators published two studies with dogs using this technique.

Study 1: The researchers recorded the barks from five adult dogs in two different contexts; either in response to an unfamiliar person approaching a garden area or when left alone, tied to a tree in a park (3). They then brought 30 other dogs into the lab and played the recordings from a hidden recorder, first allowing habituation to a particular dog/situation and then, for the dishabituation test, changing either the dog or the cause.  Results: The subject dogs consistently showed an increase in interest to the recordings in response to both a change in identity of the dog who was barking and also in response to a change in the cause of barking. These results suggest that dogs are capable of differentiating who is barking when they hear another dog and what the dog is barking about. What this study design could not tell us however, is what exact type of information (if any) the dogs were gleaning from the recorded dogs or if they were capable of identifying a known individual by his or her bark.

Study 2: This time around, the researchers asked the question – Do dogs recognize the barks of other dogs who they know and do they react to what their friends are barking about (4)?  A group of 16 dogs, all living in multiple-dog homes, were tested. The dogs were tested in their own homes (so had an attachment to the context) and they listened to a hidden recording of either an unfamiliar dog or of one of their housemate dogs (who was not present at the time, because that would just be weird). The two situations were the same – barking when left alone or barking at an unfamiliar person approaching the yard’s fence. Each dog’s reactions were videotaped to allow careful analysis of any changes in behavior while listening to the recordings. Results: The dogs showed specific behaviors that depended upon who the barker was (friend or stranger) and upon what was causing the barking (isolation or territorial). Upon hearing a recording of their housemate, dogs would move toward the house where the dog was expected to be. Conversely, they moved toward the yard’s gate when they heard the sound of an unfamiliar dog barking at a stranger. The listener dogs also barked most frequently in response to the “stranger coming” recordings, regardless of whether the bark came from their housemate or a stranger. The researchers concluded that dogs appeared to be able to identify other dogs “by bark” and that they also obtained information about a bark’s cause, simply by listening, in the absence of other cues such as the barking dog’s body language or facial expressions.

Take Away for Dog Folks:  The results of this study instruct us (once again) to take care with  our assumptions when working with dogs. While it should be naturally obvious that dogs are proficient at  recognizing and understanding one another via vocalizations and that a great deal of information is conveyed via barking (and I would bet a few of you were shaking your heads whilst reading and muttering, “well, no kiddin'”), we often do not behave as though we actually believe this to be true. Here is what I mean.

Crazy Barking

Dog owners, trainers and behaviorists frequently classify barking in dogs as a problem behavior. If we don’t like it, if it annoys us, if we deem it excessive or an attention-seeking behavior, then it immediately gets dumped into the “behavior problem” bin. Well, granted, excessive barking can be annoying, can pose a community nuisance, and as a recurrent behavior may need some modifying. (Believe me, I understand vocal dogs – I live with a Toller). However, perhaps as humans we have become so intolerant of dogs barking that we may occasionally stop seeing it for the important communication tool that it is in our efforts to stop it.



Up on the ol’ box: Moreover, we may often get it wrong.  Barking that is classified as problematic because it is thought to be “attention-seeking” could in actuality be a legitimate bid for affection from a chronically neglected dog. Or barks that an owner is instructed to ignore so as to “extinguish the behavior” may in fact be conveying true distress. (See “Is it time for the extinction of extinction?” for more about this). Is it also not possible that a dog who shows alarm barking truly has something to be alarmed about? While I am not suggesting that we should allow all dogs, at all times, to bark to their little heart’s delight (though, that is certainly what Chippy my Toller is going for), I am advocating that just as we accept body postures, facial expressions, eye contact, elimination patterns, and touch (tactile signals) as important forms of communication in our dogs, so too we should accept (and decriminalize) barking.

As trainers and behaviorists, perhaps it is time to dial back the trend towards classifying any barking that an owner does not like as “attention seeking”, “demand”, or “nuisance” barking, and reclassify it as a normal communication pattern that warrants understanding of the cause and as needed, modification. As the very chatty species that we are, we should be sensitive to and wary of any training approach or behavior modification program whose goal is to produce a completely silent dog.

As for my barking phone, I will continue to enjoy it, even if the dog is speaking nonsense. And Chippy the Toller, of course, says “Bark on, man, bark on”.

Chip Jan 2012


Cited Studies:

  1. Pongracz P, Molna Cs, Miklosi A, Csanyi V. Human listeners are able to classify dog barks recorded in differenct situations. Journal of Comparative Psychology 2005; 119:228-240.
  2. Pongracz P, Molna Cs, Miklosi A, Csanyi V. Acoustic parameters of dog barks carry emotional information for humans. Applied Animal Behavior Science 2006; 100:228-240.
  3. Molnar C,OPongracz P, Farage T, Doka A, Miklosi A. Dogs discriminate between barks: The effect of context and identity of the caller. Behavioural Processes 2009; 82:198-201.
  4. Pongracz P, Szabo E, Kis A, Peter A, Miklosi A. More than noise? Field investigations of intraspecific acoustic communication in dogs (Canis familiaris). Applied Animal Bahavioual Science 2014: In Press.

Lend a Helping Paw

Dogs are highly social beings who express their social nature in a variety of ways. They desire companionship with others and readily integrate into our human families and lives. Most of our dogs love to play and to learn new things and enjoy spending time together going for walks, a ride in the car or simply hanging out for a cuddle on the couch. Given the choice, most dogs prefer to share their days with their human family rather than alone and many also have strong social relationships (friendships) with other dogs or even with members of other species.


Canine Friendships Come in Many Forms

Although not yet studied thoroughly, dogs may also exhibit certain types of “prosocial” behavior. These are spontaneous actions that are intended to help another individual in some way, usually with no obvious benefit to the helper. Psychologists have defined four general categories of prosocial behavior. These are comforting, sharing, informing and helping. At least anecdotally, comforting is something that dogs seem to excel at.  Many dog owners relate that their dog is very empathic, seems to know when they are sad or are having a bad day, and often stays close at hand to provide comfort and love. Behaviors related to sharing may be less common, but certainly many of us have known a dog or two who readily shares his toys, bed or food with others.

sharing stick      sharing bed  Sharing water           Sharing (?) a stick                         Sharing a bed                       Sharing a drink

What about the most complex prosocial behavior – Helping? There is no doubt that dogs can be successfully trained to help humans. Examples abound and include dogs who aid the disabled, move or protect livestock, find illicit contraband, and perform in search and rescue operations. The number and variety of trained skills that dogs use to help us are both vast and impressive. However, prosocial helping is a bit different because this type of aid occurs spontaneously with little or no former training. Prosocial helping behavior is intrinsically (internally) motivated by empathy or a sense of community and occurs without an obvious or anticipated reward to the performer.

For dogs, this form of helping is considered to be a relatively complex social behavior because it requires two things. First, the dog must understand the goal of the person who is in need. Second, the dog must be motivated to help the person to achieve that goal. For example, in the case of helping a person to find something, the dog has to understand that something is hidden/lost and that the owner is searching for it (and wants it) and must also have a desire (i.e. be motivated ) to help the person to find the object. It is this second component of helping, the intrinsic or internal motivation to help others, that a group of researchers at the Max Planck Institute for Evolutionary Anthropology in Germany recently studied. They asked the question: “Are dogs inclined to lend a helping paw?

The Study: The researchers conducted a series of four experiments to determine whether dogs would come to the aid of a person who was attempting to enter another room to retrieve a set of keys. The same scenario was used in each experiment, but the identity of the person and the way in which the person communicated his goal to the dog were varied.

  • Door opening behavior: Prior to the start of the experiments, dogs were trained to open a plexiglass door that entered into a small room (i.e. the target room) by hitting a button that was positioned on the ground in front of the door. Dogs and people could easily see into the target room. The dogs were trained to hit the button and open the door via shaping and positive reinforcement (food treats). This training took place several days prior to the actual experiment and only dogs who successfully learned to hit the button were included in the experiment. The behavior used for opening the door was purposely trained without a cue, to ensure that the dogs learned how to open the door but were not trained to respond to a specific command to do so.
  • Experimental conditions: During each experiment, a researcher or the dog’s owner communicated to the dog their desire to enter the target room by one of several means. These included either pushing on the door, reaching for the door, pointing at the button, using gaze (either into the room alone or alternating between the room and the dog), talking (general terms), commanding the dog, or a combination of spontaneous (natural) communicative gestures. In all conditions, the goal that the owner or experimenter was attempting to communicate to the dog was that they needed to enter the target room to retrieve the keys that were on the floor. (Note: Keys were purposely used as an object that would have no or little value to the dogs, thus ensuring that their inclination to help was not motivated by a desire to retrieve a toy or to obtain food). In each experiment, the control was a person who sat near the dog but did not communicate a desire to enter the target room.

Results: Dogs were highly likely to help in two primary conditions. These were either when the person used pointing gestures that were directed toward the button that opened the door or when the person used a variety of “natural” communication gestures simultaneously such as gesturing, talking, gazing and pointing to express their goal. Interestingly, the person’s identity did not influence the dog’s response. Dogs were as likely to help a stranger as they were to help their owner. The researchers concluded that the dogs in this study were highly motivated to help a human when the person’s goal was clearly communicated using either a common communication signal (pointing) or a variety of naturally selected gestures in combination. They suggested that an absence of helping behavior in dogs may be more likely occur when dogs do not understand the person’s goal,  rather than due to the lack of an intrinsic desire to be of aid.

Helping Dog

Will your dog lend a helping paw?

Take Away for Dog Folks:

  • It’s all about communication: The results of this study emphasize some important issues about how we communicate with dogs. When isolated gestures or verbal commands were used to attempt to communicate the person’s goals, dogs did not perform well. Give this a try and see how unnatural it feels. Point or gaze at something near your dog but do not use any additional words, body language or gaze. Does your dog respond? (Mine did not – they just looked at me like I was a crazy person). Conversely, when owners were instructed to just “communicate naturally” with their dog using a myriad of signals, the dogs’ understanding and success increased dramatically. While this difference is not all that surprising, it is important information for trainers and owners to keep in mind. Simply issuing a command or gesturing stiffly won’t cut the mustard with most dogs. Similar to communicating with the humans in our lives, effective communication with dogs includes a variety of  simultaneously delivered verbal and non-verbal signals – signals that can be messy and complex and difficult to define, but ultimately that are most successful at getting the message across.
  • Imperative versus informative gestures:  Researchers who study dog cognition are interested in whether dogs are capable of understanding human communicative gestures as being informative (i.e. providing helpful information) rather than interpreting them only as imperative (i.e. as a command to do something). This is an important distinction because while it is well-known that dogs can be trained to perform quite complex tasks and respond to trained cues, there is not that much scientific evidence showing us that dogs regularly use human behavior as information (although anecdotal evidence of this certainly abounds). The results of this study, and a few others before it, suggest that dogs are capable of perceiving certain human gestures, such as pointing and gazing, as information and that they may subsequently use that information to act (and help).
  • Empathy – Yep, they got it. There is no doubt that dogs are of great help to us, in a myriad of ways. We train dogs to aid the disabled, protect us, find lost children, and comfort the ill. However, that type of helping (while noteworthy and admirable in its own right) differs qualitatively from spontaneous helping in which the dog perceives a need and, presumably motivated by empathy, reacts by providing aid. It is this latter form of helping that was tested in this study. The cleverly designed set of experiments showed that when the goal of the person was clearly communicated to the dogs, many immediately helped the experimenter – and did so even when there was no obvious reward available to them. While all dog lovers know in our heart of hearts that our dogs express love, concern, and even compassion for others, here is some science showing us that contrary to the beliefs of an ever declining few, humans do not have a corner on the empathy market. Once understanding is achieved, our dogs are willing to  help us – even with something as mundane as helping someone to enter a room to retrieve some keys! (Just think about what they may be capable of when we really need their help). Have some fun – Test your own dog and find out if he is willing to lend you a helping paw!
Helping Dog

What does your dog help you with?

Reference: Brauer J, Schonefeld K, Call J. When do dogs help humans? Applied Animal Behaviour Science 2013;148:138-149.

I Yawn for Your Love

Vinny, my Brittany, yawns a lot. He yawns first thing in the morning when he rises, in the evening when he is tired, and many times in between. We notice this because Vinny emits an adorable little squeaky sound whenever he launches a particularly wide and emotive yawn. We also know that Vinny seems to be highly susceptible to contagious yawning. If Mike or I or one of the other dogs yawn when we are close by, Vinny immediately joins in.

Vinny Yawns


Recently, I was delighted to find a series of research studies examining the phenomenon of yawning in dogs and their people. The primary objectives of these studies were to determine if dog yawning, traditionally believed to be a mild stress response, is in actuality (or additionally) a reflection of social contagion and empathy.

Yawning Dog Wolfhound


Background information: Contagious yawning is a well-established phenomenon in humans. Not only are most of us easily induced to open wide when someone nearby emits a yawn, there is evidence that even just hearing a yawn noise or watching others yawning on a video are sufficient to trigger a yawn response. (Indeed, I would venture that simply reading the previous two sentences, in which the word “yawn” occurs six times, caused more than a few readers to……yawn).

There are several theories that attempt to explain why yawning is socially contagious. At the simplest cognitive level, group yawning may just reflect unconscious mimicry, a form of priming (see “The Steve Series” for a discussion of priming in dogs). This is the most parsimonious view as it does not require emotional attachment between the yawner and the “yawnee” and does not require the ability to empathize (or have a “theory of mind”). Alternate theories place contagious yawning somewhat higher on the social cognition scale and suggest that it represents an involuntary empathic response. In other words, people yawn when others do because they feel the same (i.e. empathize). According to this view, people should be more likely to yawn in response to others who they know well and have an emotional bond with than when they are with unfamiliar yawners. In recent years, data show that this is indeed true. Additional studies showing that people who score highly on psychological tests of empathy are more susceptible to contagious yawning have tipped the evidence scale towards the empathy theory (at least for people).

What about dogs? Although spontaneous yawning occurs in many mammals, contagious yawning has only been described in humans, chimpanzees, and in recent years – in dogs.  Studies with dogs have asked three primary types of questions:

  • Do dogs exhibit cross-species contagious yawning? In other words, does seeing a human yawn increase the likelihood that a dog will respond with a yawn?
  • If it does occur, is it a type of empathic response? Are dogs more likely to yawn in response to someone they know and share an emotional bond with than they are in response to a stranger? If so, does contagious yawning have a communication function?
  • And, a related question that is of interest to most trainers – May contagious (or spontaneous) yawning be simply a stress response that occurs during times of low or moderate anxiety? If so, is there a contagious component to it?

The Studies: The first published study of dog yawns appeared in 2008 in a paper entitled “Dogs Catch Human Yawns” (1). The researchers studied a group of 29 dogs and found that 21 of the dogs (72 %) demonstrated contagious yawning when sitting near an unfamiliar (yawning) person. The control group (eye contact plus non-yawning mouth movements) elicited zero yawns. This was pretty impressive, seeing that rates reported in humans range between 45 and 60 % and chimps come in at a paltry 33%. Although this study demonstrated yawn contagion, the design of the study did not allow the researchers to determine if the dogs were yawning as an expression of empathy or as a stress/anxiety response. Other researchers decided to study this further:

  • Nope, ain’t happenin': A 2011 study compared yawn rates in dogs who were exposed to the yawns of either their owner, a stranger, or another dog (2). They also compared pet dogs living in homes with rescue dogs living in a shelter. Although they saw a bit of yawning (~ 26 percent of dogs), the rates did not differ significantly from control rates for any of these conditions. These researchers concluded that they found no evidence for empathy-based contagious yawning in dogs.
  •  Listen……there it is! This study took a different approach; they recorded the sound of yawning in 29 dog owners and then played these recordings back to each owner’s respective dog (3). The dogs were also exposed to the yawn sounds of an unfamiliar person and to familiar/unfamiliar non-yawn sounds (controls). Hearing the sound of yawning caused a response in 41 percent of the dogs and the sound of a familiar yawn elicited significantly more yawns than did the sound of an unfamiliar yawn. (Additional analysis of the data collected in this study suggested that stress-induced yawning was not an underlying cause of dog yawning, lending support for the social (empathy-based) theory [4]).
  • I yawn for you: This 2013 study was specifically designed to test whether contagious yawning in dogs was a result of stress or if it reflected an empathic response (5). The researchers monitored dogs’ heart rates during each condition as a measure of physiological stress. Testing 25 dogs, they found that dogs did indeed demonstrate contagious yawning, that dogs yawned significantly more frequently in response to their owner than in response to an unfamiliar person, and that heart rates did not increase significantly during the experiment. Their results lend support to the hypothesis that dogs show contagious yawning with humans and that this behavior is socially modulated (i.e. empathy-based) rather than  stress-based.
  • But wait……do dogs also stress yawn contagiously? The most recent study, published in 2014, shows just how complicated the dog yawning story may actually be (6). Changing things up a bit, this group of researchers worked with a group of 60 shelter dogs and exposed them to a yawning (unfamiliar) experimenter. They measured both yawn responses and salivary cortisol levels, which like heart rate are expected to rise during periods of physiological stress.  Contagious yawning in the shelter dogs occurred in only 12 (20 %) of the dogs, but interestingly, it was those dogs (the yawners) whose cortisol levels were increased. These results suggest that stress yawns can also occur contagiously.
Stress Yawn


Take Away for Dog Folks: Taken together, the results of these studies suggest that yawning in dogs may be context-specific, having different functions depending upon setting and situation. Similar to several other species, dogs do appear to yawn during periods of mild stress, possibly as a displacement behavior. In these cases, the yawn is accompanied by other communicative signs of tension such as a lowered body posture, panting, pacing or whining. [Note: While some posit that dogs yawn as a signal to “calm” other dogs or people, there is no empirical evidence to support this belief]. The data in these studies suggest that a stress yawn may also occur “contagiously” when faced with an unknown person in a new setting, perhaps as a result of the person (or her yawns) causing an increase in tension in the dog. Conversely, contagious yawning that occurs in a relaxed and happy dog, typically in response to a familiar person, may signify a type of social communication that reveals some level of empathic response. In those cases, what exactly is being communicated (“I’m tired too” or “This TV show is boring; can we please turn Lassie on”, or “Let’s go for ice cream!”) is still open to debate. 

Cited References:

  1. Joly-Mascheroni RM, Senju A, Shephred AJ. Dogs catch human yawns. Biology Letters 2008;4:446-448.
  2. O’Hara SJ, Reeve AV. A test of the yawning contagion and emotional connectedness hypothesis in dogs, Canis familiaris. Animal Behaviour 2011;81:335-340.
  3. Silva K, Bessa J, Sousa L. Auditory contagious yawning in domestic dogs (Canis familiaris): first evidence for social modulation. Animal Cognition 2012;15:721-724.
  4. Silva K, Bessa J, deSousa L. Familiarity-connected or stress-based contagious yawning in domestic dogs (Canis familiaris)? Some additional data. Animal Cognition 2013;16:1007-1009.
  5. Romero T, Konno A, Hasegawa T. Familiarity bias and physiological responses in contagious yawning by dogs support link to empathy. PLoS ONE 2013:8(8):e71365.
  6. Buttner AP, Strasser R. Contagious yawning, social cognition, and arousal: An investigation of the processes underlying shelter dogs’ responses to human yawns. Animal Cognition 2014;17:95-104