Tuesday, July 28, 2015

Dogs and brains link fest

I've been doing a lot of writing, actually, but none of it on this blog. Right now I'm working on an NSF grant proposal. This is really exciting for our lab, but it's a lot of writing! I'm also working on a piece for the writing group I was assigned to as part of attending the upcoming ComSciCon-Chicago, a science communication conference, and I just recently submitted another story to a dog-focused magazine (I'll report here when it's published).

As a result, I haven't found the time to write any new blog posts. But there's lots of other stuff for you to read out there, and I report the best of what I find on my Twitter feed. Here are some recent ones:

Tuesday, May 19, 2015

Learn Science free online!

There’s lots of science out there to read about on the internet these days (so go get reading)! For people who came to science after their formal schooling is over, it can be hard to know how to get the basics to understand all this stuff. And I do think it’s important to understand the basics — a solid knowledge of biology is invaluable when you’re trying to figure out if the findings that a starry-eyed science journalist is reporting are as important as they sound, and whether the journalist’s coverage of them is critical enough. (Uncritical science reporting? Oh yeah. There is way too much of it in the world.)

So how do you go about learning Science? Here are some upcoming free online courses that I recommend to you. By the way, if you are a certified trainer or behavior consultant, I recommend you ask your CEU distributor of choice to give you CEUs for taking these classes. They are absolutely relevant.

Animal Behaviour, University of Melbourne (Coursera)


Starts: June 1

This course is about the behavior of wild animals and about the academic study of animal behavior. It’s a different perspective than the applied behavior approach that most trainers are familiar with. According to the course web page, it covers the following topics:
  • Behaviour, Ecology and Natural Selection
  • Genes, Environment and Learning
  • Finding food and avoiding predators
  • Communication
  • Sexual selection and sperm competition
  • Mating systems and sex allocation
  • Parental care and conflict
  • Social behaviour
 Coursera courses are free, but if you want a certificate that proves you took the course, you will have to pay $50.

Essential Human Biology: Cells and Tissues (EdX)


Starts: June 10

Cells: the things that send information around the brain; the things that make and secrete hormones; the things that are responsible for every part of our life. Whenever I teach about neurobiology or hormones to trainers, I wish I could depend on them having a solid cell biology background!

Just as above, EdX courses are free but you must pay $50 if you want a verified certificate.

Introduction to Psychology, St. Margaret’s Episcopal School (EdX)


Starts: June 15; self-paced

I loved taking basic psychology. I’m sure this course will be quite human-focused, but some of the concepts are applicable to other mammals as well. Others are perhaps applicable to working with the human side of the equation. This course reports to cover:
  • An understanding of what psychology is and its history
  • How brain structures function and how neurotransmitters influence behavior
  • Concepts of how we learn as well as components of emotion
  • How a child's mind and personality develops
  • Discover classifications of abnormal behaviors
This course is “self-paced,” meaning that you can take it at your own pace over the course of several months if you so choose. Price as above.

If you think you might take one of these, I would love to hear about it in the comments!

Saturday, May 9, 2015

Can a supplement improve a dog's response to training?

Ah, the sharp focus of a German shepherd.

When I was in veterinary school, my roommate had a dog nicknamed Mr. C who had some focus issues. (She still has him, but is sadly no longer my roommate.) We used to joke that C had attention deficit hyperactivity disorder (ADHD); he just had an extreme case of not being able to keep his mind on one thing for any length of time. Training him was challenging. Hed get excited and then seemed to be unable to absorb new ideas.

I thought of C when a former student of mine, Melissa Hartley, pointed me at this article:

Kano, Masaaki, et al. "Oral tyrosine changed the responses to commands in German Shepherds and Labrador Retrievers but not in Toy Poodles." Journal of Veterinary Behavior: Clinical Applications and Research (2015). http://dx.doi.org/10.1016/j.jveb.2014.12.009


Although ADHD isn’t a formal diagnosis in dogs currently, the authors of this paper hypothesized that a dog’s focus during training may affect their learning just as a human child’s focus can affect their learning. Human children with ADHD seem to have differences in levels of adrenaline and noradrenaline in their bodies, and their learning abilities appear to improve when they are given medication to modify those levels. The authors hypothesized further that giving dogs a supplement which is a building block of adrenaline and noradrenaline could improve their response to training by improving their ability to respond to the task at hand.

Adrenaline (also known as epinephrine) is the hormone that you can feel shooting through your body when you’re startled, during the fight-or-flight response. Noradrenaline (norepinephrine) is a close cousin with similar effects. It seems counter-intuitive that giving a hyperactive child (or dog) a supplement to increase this hormone which is associated with being overly excited should help them focus, and yet this is the pathway that Ritalin (methylphenidate) uses quite successfully to help children with ADHD improve their focus. The brain is a complicated organ, and the effects of moderating particular substances in different areas are unfortunately not always intuitive.

This study looked at the effects of supplementing dogs with tyrosine, an amino acid which is known to increase the levels of adrenaline and noradrenaline in the brain. The question asked in this study was: would supplementing dogs with tyrosine improve their response to training?

The study methods

Three breeds of dogs were tested in the study: German shepherds, Labrador retrievers, and toy poodles. The GSDs and labs were at a training facility for police dogs, while the toy poodles were at a different type of facility. All dogs received three training sessions to learn to sit. Then some of them received a daily tyrosine supplement for three days, and a control group did not. At the end of the three days, both groups were trained again. Urine samples were taken both before and after each training session to test for levels of adrenaline and noradrenaline in the urine.

The training approach appears to have been based on operant conditioning: capturing the sit behavior via a food reward and associating it with a verbal cue.

The results

Dogs were divided into high achievement versus low achievement groups based on the number of times the dog sat after being given the cue. High achievement dogs sat frequently after receiving the cue, suggesting a better response to training in this group.

The urine of all dogs was tested before tyrosine supplementation. Levels in the urine of the toy poodles were significantly lower than the levels in the urine of the GSDs and labs. The poodles also appear to have responded correctly to the sit cue less often than the GSDs and labs in the initial training sessions, though this data isn’t clearly represented.

After three days of tyrosine supplementation, dogs were trained again and compared to control dogs who did not receive supplementation. Did dogs given tyrosine improve in their response to training, compared to dogs who were not?
  • German shepherds: yes
  • Labrador retrievers: yes
  • Toy poodles: no
And they really did improve: the tyrosine-supplemented GSDs and labs responded to the sit command correctly about twice as many times as did the control dogs. The poodles’ performance actually improved a little as well, but the difference was not statistically significant.

Why the breed differences in response?

Why did the GSDs and the labs seem to respond so well to the tyrosine supplementation, and the poodles did not?

Now, with caveats that looking at urinary levels of adrenaline is not the same thing as looking at brain levels of adrenaline (it’s just a lot less invasive to do), it’s very interesting that the toy poodles had lower levels of adrenaline before supplementation than the GSDs and labs did, and that their response to supplementation was different. If we take as a given that toy poodles are harder to train than German shepherds (and I’m pretty comfortable saying that, just from what I know about the two breeds), could part of the reason be a difference in brain levels of adrenaline making it harder for the toy poodles to focus?

Why wouldn’t the toy poodles respond better to the supplementation, then? It’s hard to say. Perhaps the adrenaline pathways in toy poodles function so differently from those of the other two breeds that the supplementation was just insufficient. It’s also possible, of course, that there were confounding factors in this study — for example, the fact that the toy poodles were being raised in a very different environment from the police dogs in training.

Will tyrosine supplementation help my dog focus better?

Who knows? This was an initial study. If you think that your dog is difficult to train because of focus issues, my first suggestion to you would be to make sure you’re making training fun and providing sufficient incentive (treats, opportunities to play).

I would have loved to have seen video of the training techniques used in this study. Were they good techniques, or perhaps could have different techniques been just as effective as tyrosine supplementation?

Was tyrosine supplementation actually effective in these dogs? I’d want to see another study or two looking at more breeds before I was comfortable with the results of this one. Again, it’s hard to trust just a single study; there could be factors at play that don’t come out until the hypothesis has been tested in more situations.

If you really want to pursue this supplementation, be sure to do so with your veterinarian’s approval so you don’t jeopardize your dog’s health.

Thursday, April 23, 2015

Should dog training be 100% positive?

This dog is clearly enjoying being trained.

There's been an interesting discussion recently on a mailing list for animal behavior consultants and hangers-on like myself. (The group is the International Association of Animal Behavior Consultants, IAABC.) These highly-skilled behavior consultants are knowledgeable in how to deal with behavior problems in dogs and other species, rather than focusing on basic obedience or competition skills like agility.

As you may already know, the modern dog training world can be described as split into two factions: those who advocate methods using dominance theory and/or force, such as alpha rolls or leash popping, and those who advocate methods using learning theory and specifically operant conditioning, such as clicker training.The behavior consultants on this list all fall solidly into the latter category, and all agree that the basis of training should not be founded on punishment-based techniques. They are hashing out the question: Is it ever appropriate to use aversives in training a dog?

Because the two factions split mainly on the use of punishment, it can be easy to fall into black-and-white thinking and assume that any aversive is unacceptable, and equate all aversives with pain and fear. But does “aversive” necessarily mean “painful”?

An aversive is something unpleasant. Give an animal something pleasant (a treat) and it will be more likely to repeat whatever behavior it most recently offered (sitting down). Give an animal something unpleasant (a tug on a prong collar) and it will be less likely to repeat whatever behavior it most recently offered (lunging at a passing dog). Both techniques work in getting the desired behavior. Techniques using an aversive stimulus may have side effects, however — in this example, a dog who lunges at passing dogs out of fear may learn to associate pain from the prong collar with other dogs. While he may stop lunging, he is likely to develop other unwanted behaviors, like biting when the other dog approaches close enough.

Pain and fear are absolutely aversives, and I think everyone in this discussion is agreed that pain and fear should be avoided — that some aversives are just too aversive to use. Many trainers in the discussion declare that they would never use a shock collar; some say they might, but only under extreme circumstances, after many other approaches have been tried and failed. Where do you draw the line at “too aversive,” though? That’s a very interesting question, and different trainers have different answers. But can you be a trainer who works in the positive training camp, and still sometimes uses aversives? For sure.

And here’s the thing: it’s the dog who determines what’s aversive. So some tools that we think of as very mild, like a head halter, can end up being quite aversive for some dogs. A head halter — that’s nothing like a prong collar or a shock collar or a choke chain, and it doesn’t hurt the dog at all. But it is (according to many dogs, including one of mine) incredibly annoying to have on your nose. Is it aversive? Yes. Is it inhumane? That’s an awfully strong word for such an innocuous device. But if you use a head halter on your dog, you are not engaging in 100% positive training. You are using a (mild) aversive. Not one that probably involves pain or fear, but an aversive all the same.

And it turns out it’s pretty difficult to train successfully using no aversives at all! Even telling a dog “that wasn’t the right choice” by using a marker like “oops!” during your training can be a mild aversive. Is it okay to train with mild aversives? Everyone has to answer that question for themself, but from my perspective, of course it is. Life has its ups and downs and everyone is going to encounter mild obstacles from time to time, even a pampered dog. The question is how big an aversive you want to throw at your dog, where exactly you draw the line between acceptable and not. That line will be drawn differently for every owner and every trainer.

So when you’re choosing a new trainer for your dog, remember that some will advertise that they use 100% positive methods, but they may not have quite thought through the implications of all of their methods. Others may state that they’re not 100% positive, but that they still use mostly positive methods — and that’s okay. As your dog’s owner and advocate, it’s up to you to talk to your potential new trainer about their methods, discover what kinds of aversives they do use, and decide what’s acceptable for your dog. Just work through the language your trainer uses to make sure that the kinds of aversives they use are at a level that’s acceptable to you, and of course make sure that they use scientifically-based learning theory (look for words like “positive reinforcement” and avoid words like “alpha” and “dominant”). As a dog loving community, we can agree that the use of aversives should be minimized, while still accepting that from time to time it’s okay to use mild ones.

Monday, April 13, 2015

A week of tame foxes

“You're checked all the way through to... some place I can't pronounce,” said the woman who was checking me in at my small local airport in Illinois.

Novosibirsk. It is the third largest city in Russia, located in south-western Siberia. It is the location of the Novosibirsk State University, one of the best universities in Russia, where the Institute of Cytology and Genetics maintains Belyaev’s tame foxes.

(You may already know about the fox domestication project, but if you don’t, Wikipedia has a good primer, and Jason Goldman has written about them.)

The Institute is actually in Academic City (Akademgorodok), a suburb of Novosibirsk. Academic City is an odd blend of the European — my hotel would not have been out of place in France — and the Russian, with its thick stands of birch and fir. During my early April visit, there was still three or four feet of packed snow on the ground, and mud season was commencing as the temperature rose.

The Institute is in a green-roofed building shoulder-by-shoulder with other university institutes. The farm, where the foxes live, is a ten or fifteen minute drive out of the city. I went to the farm daily to study the socialization period in tame and aggressive fox kits.

Tame fox kit (silver color)

I was working with these kits at three weeks of age, before they were old enough to start venturing out of the nest and interacting with the world. At this point they shouldn’t yet have entered their socialization period. Yet you could already tell the difference between the tame kits and the aggressive kits. Kits within a group weren’t identical in behavior: some complained about being restrained, some yelled, some fell asleep, some were calm and silent. However, the aggressive foxes tended to make more noise, and the tame foxes tended to be more curious about their surroundings. Two aggressive fox kits tried to bite. One tame kit did.

As for the adults, I found more behavioral variation than I’d expected there as well, although the head of the laboratory where I work had warned me again and again that the foxes vary sigificantly in behavior. Tame foxes were curious and wanted to interact with us, but some were shy, diving into their nest boxes or to the far side of their cage and then returning slowly. One fox stretched his body out, low to the ground, so that he could sniff my companion’s face without having to commit himself to coming too close. (When I offered to let him sniff my face, he stole my hat and then carried it around his cage while the neighboring foxes watched in fascination.)

Slightly shy tame fox (Georgian white color)

Other tame foxes could not contain their enthusiasm at having people to interact with. They rolled on their backs and made excited yipping noises and wagged their tails. In their joy, they would hold our hands gently in their mouths, something I saw again and again with them but that I have very rarely seen a dog do.

Fox holding my hand in his mouth (platinum color)

I visited foxes from the control line, who had not been bred for behavior. They were simply afraid of us: when their cage door was opened, they retreated. If cornered, they would bite, but any aggression they showed was entirely defensive.

I also saw foxes from the line that has been selected for aggression to humans. Some of them were afraid and aggressed only defensively. Some were more scary, coming forward to the front of the cage to bite again and again. Certainly they were afraid of humans, but something in their brains or hormones makes them more proactive and less passive in their defensive aggression.

Finally, I met rats and mink selected for tameness or aggression. The tame rat that I met was happy to be held and happy to interact with me, but I don’t have enough experience with pet rats to say if this was unusual. The aggressive rat that I met was terrifying, hurling herself at a gloved hand when her cage door was opened and screaming repeatedly, even after we backed off.

The tame mink were less curious than the tame foxes and didn’t seek interaction with humans in the same way. One let himself be held by his keeper but I wasn't allowed to touch him, in case he might try to bite.

Tame mink

Notice the little white patch on his chin — more white coloration is associated with more tameness in both minks and foxes. Another, all-white mink was tamer and I could pet him. He seemed deeply passive, not seeking interaction, just tolerating it.

Tame white mink

Remember that part of the tame fox story — that as the foxes were selected for tame behavior, they started showing characteristics typical of domesticated species, including white patches and curled tails? Only a small percentage of the tame animals have these features, but I saw several piebald fox kits:

Piebald fox kit (silver color)

...and my host kindly pointed out one fox with a gorgeous example of a curled tail.

Fox with curled tail

What an amazing week. I kept thinking: how strangely my life has turned out!

Wednesday, March 25, 2015

Who funds dog research?

As I move through my training and think ahead to my future career, I wonder: who will pay for all this research I want to do on dogs? I have so many questions to ask!
  • What changes happen in the canine brain as it enters, and then leaves, the socialization period?
  • How is the brain of a fearful dog different from that of a confident dog?
  • What are the genetic differences behind these variations?
  • How do environmental differences (prenatal stress, early learning, adult life) change the brain?
In other words, what are the mechanisms in the brain that differ in fearful dogs — receptors, neurotransmitters, synaptic wiring? And how can I learn about them without using invasive (painful and/or terminal) techniques?

Who are the caretakers of Dog, the species, who care about fearfulness? We as dog owners and lovers care, but dog owners and lovers aren’t the ones who are trained to heal unhealthy dogs, to perform research aimed at understanding them, and we (mostly) aren’t the ones who breed them. So who are the groups who are the caretakers of Dog, and what subsets of Dog do they care for?

Image: Who is my caretaker?


We (I am a veterinarian) are trained to heal sick dogs. Relatively few veterinarians perform research compared to those who engage solely in clinical practice. But some do perform research: most commonly as faculty at veterinary schools alongside a clinical practice, or less commonly as researchers without a clinical practice at research instititutions.

Veterinary research, as a result of this strong emphasis on healing the unhealthy, is focused on clinical results. Veterinarians most commonly perform research which asks questions about the effectiveness of particular techniques — medications, surgical approaches, new equipment. Veterinary research very rarely addresses root questions about mechanisms, particularly in the area of behavior. Rather than asking “How are the brains of fearful dogs different?”, veterinary research is more likely to ask how we could fix a fearful dog: “Does this medication make a fearful dog less fearful?”

In fact, as I pursue my mechanism-based questions, I am asked if I miss being a veterinarian. The perception is that because I am engaged in basic, rather than clinical, research, I am no longer working as a veterinarian.

Basic science researchers

If veterinarians do clinical research studies, then who does basic research biomedical studies, studies that look not at how to fix problems but at how the body works? Ph.D. researchers are more likely to do this sort of research, which is why I am currently engaged in obtaining a Ph.D.

Traditionally, Ph.D. researchers have not been interested in dogs. In fact, way back in 2004 when I was originally deciding between a Ph.D. and a D.V.M., I was told by a Ph.D. animal behaviorist, “Ph.D.s don’t study domesticated animals. Veterinarians study those.” (Actually, veterinarians mostly just try to fix unhealthy domesticated animals, not study the healthy ones.)

That perception has changed in a big way in the intervening eleven years. There are now multiple laboratories studying dogs. But where does their funding come from — who cares enough about dogs as dogs, not as models for human problems, to provide the impressive funding needed for a genomics study? (The work I am doing for my Ph.D., sequencing messenger RNA, costs around $45,000.)

The U.S. federal government

The traditional source of funding for basic research is the federal government: the National Institutes of Health for health-based research and the National Science Foundation for more basic research. But these two massive institutions are very much focused on human health — as they should be, as they are funded by the tax dollars of American citizens. The economy can’t support all the research American researchers would like to do, and getting an NIH or NSF grant is becoming more and more difficult as grant funding is cut. Funding to study dogs as models of human disease? Maybe, but isn’t it easier to study laboratory rodents (on which you can perform invasive studies) or work on humans directly? Funding to study dogs as dogs? Go lie down until it passes.

In my experience, the small number of laboratories directly studying dogs are either studying them as models for questions about human health or evolution, operate on a shoestring budget, or have great trouble obtaining funding for what they want to do.

Animal welfare organizations

So who cares about dogs? Animal welfare organizations, some of which are national in scope and do perform research. Some major players in this field are the American Society for the Prevention of Cruelty to Animals (ASPCA), the Center for Shelter Dogs (CSD), and the Humane Society of the United States (HSUS). I am most familiar with the research coming out of the ASPCA and the CSD, and it is exciting stuff. But it is again mostly focused on applied questions: how can we help the shelter dogs in our care?

I reviewed some of the research these two organizations have performed on how to identify and treat food aggression in shelter dogs in my story for the Bark on shelter behavioral assessments. This was ground-breaking research and I am really glad to see it published. But it doesn’t ask the basic (i.e., non-applied) research questions I am interested in: what is it about the brains of these dogs that differs from the brains of dogs without food aggression? That kind of research doesn’t have immediate applied benefit. You can’t take it to a shelter worker with a recommendation about whether or not to put a food aggressive dog on the adoption floor. It is incredibly impressive that these shelter-focused organizations perform any research at all, and it is absolutely appropriate that the research they perform should have a highly applied focus, with clear questions that, when answered, will provide guidance on how to improve the lives of shelter dogs, immediately. They do not have the resources to pursue these sort of mechanism questions that I want to ask, which do not have immediate applicability.

So who cares about understanding how dog brains work, with the hope that that information will provide a base for future applied research? Who cares about the whole species, not just the subset in shelters or the subset in hospitals?

Breed organizations

Breed organizations care very much about the health and welfare of dogs, and in fact have provided funding into the mechanisms behind health issues specific to their breed. A recent paper about associations between spay/neuter status and health issues in Golden Retrievers was partially funded by the American Kennel Club’s Canine Health Foundation (AKC/CHF), and a similar study on Vizslas was funded by the Vizsla Club of America Welfare Foundation. (I blogged about these studies elsewhere.)

These organizations can fund basic research on how and why particular diseases occur in their breeds, and may even be willing to fund expensive genetic studies, such as a recent one on the genetics of cancer in Golden Retrievers, supported in part by both the AKC/CHF and the Golden Retriever Foundation. However, their focus is very much on the problems of a particular breed. My questions are broader: why do dogs of all breeds have different personalities, some more or less fearful? These organizations are really the caretakers of breed subsets of Dog, not of Dog itself.

Who, then?

Who does that leave as a group willing to fund studies on Dog? On problems common to all breeds? On problems which may or may not provide good models for humans? If I hope to one day run a laboratory which studies these problems, who can I hope to help pay for the research?

I would be remiss if I did not mention Morris Animal Foundation here. While their important Golden Retriever Lifetime Study happens to focus on the health issues of a single breed, their mission is to fund research into studies of small animals (dogs and cats), livestock, and wild animals, with no breed limitations. This group is doing important work, and I applaud them.

But one organization is not enough for a laboratory to depend on for survival, especially in these times with research funding so hard to come by. And so I wonder: are we, the dog lovers of the world, the ones to start supporting research into what it is to be a dog? We, who own dogs of all breeds and mixes, with all sorts of problems, who know what problems most plague us as owners — not just medical problems, but behavioral ones?

And so I leave you with my dreams of crowdfunding, in which a researcher proposes a study and asks the public to support it through donations. Such an approach allows the dog community to take the task of answering basic questions about Dogness into their own hands. This direct connection between a researcher and the community affected by their research is a new benefit of this age of social media. Is this approach right for this particular problem? Time will tell.

Image: Will crowdfunding work?

Monday, March 9, 2015

Contexts and cues: the reactive dog brain

A dog on leash, seeing another dog, explodes into a fury of barking and lunging. Reactive dogs, dogs who respond with arousal or aggression to what should be innocuous stimuli, can be very difficult for their owners to manage safely. I've written previously about hormonal changes in individuals experiencing this kind of arousal. But why do their brains trigger the stress response in such inappropriate situations in the first place?

Learning and memory

Past learning, stored as memories, has a lot to do with current behavior. If a dog has made bad associations with something in the past, he has a good chance of expecting a similarly unpleasant experience the next time he encounters it or something that reminds him of it. How he chooses to deal with this situation — aggression or withdrawal — is one interesting question, but right now I’m writing about how he makes associations in the first place and how he retrieves them later.

Learning and memory can mean a lot of different things depending on their context. I’ll be using them in a very narrow sense.

Learning: making an association between a stimulus and a consequence
Memory: the ability to retrieve a previously-formed association
So if a puppy is attacked by another dog, he may learn to associate other dogs with pain and fear. When he later encounters another dog, he uses his memory to retrieve that association. Two parts of the brain which are deeply associated with this type of learning and memory are the amygdala and the hippocampus.

The amygdala is associated with threat evaluation: is that twisty shape I see out of the corner of my eye a stick, or a poisonous snake? Is the dog I am greeting friendly, or about to attack me? People with damage to their amygdalas may have difficulty evaluating threats, to the extent that they may not be able to feel fear. As a result, the amygdala functions in emotional learning: people told scary stories remember them better than less exciting stories partly because of the emotional contributions of their amygdala, which tells them that an experience has some level of threat and should be recorded in memory with particular care.

The hippocampus, on the other hand, is famous for its contributions to learning different locations. London cab drivers must spend years memorizing the twisty street map of their city, and when they are done, their hippocampuses are actually larger in size compared to people who haven’t gone through the training.

When they work well, these two brain structures are an important part of the process of identifying appropriate threats and discarding stimuli that aren’t threatening, based on previous experience. So what exactly is going on when they operate as they should?

Fear conditioning: contexts and cues

The most effective studies that have been done to determine exactly how the hippocampus and amygdala function in learning and memory have used fear conditioning, often in laboratory rodents. Dog trainers use classical conditioning to associate stimuli that a dog considers threatening with something positive, to change the dog’s emotional response to that stimulus — for example, to teach a dog who fears other dogs that they will reliably get food when other dogs approach, so that the dog comes to look forward to the approach of another dog as a chance to get a treat. Fear conditioning researchers do the opposite, teaching a laboratory rat that something previously benign (like the sound of a bell) predicts something aversive (like an electric shock).

It’s unfortunate that so much research has been done on how to teach fear, something we don’t actually want to do in real life. However, what we learned from these studies should translate to the types of classical conditioning we do with dogs, and be even more relevant to helping us understand how fear-based behavior issues come about in the first place.

These studies have shown that that contexts and cues are important in classical conditioning. If you put a rat into a blue cage and then repeatedly play a bell right before shocking him, he will learn to fear the sound of the bell. The blue cage is the context; the bell is the cue. If you move the rat into a purple cage and play the tone without a subsequent shock, the rat will learn that the purple cage represents a different context, and that he does not need to fear the cue in that context. So the cue and the context contribute differently to classical conditioning.

Source:  Nature Reviews Neuroscience 14, 417–428 (2013)

In the case of a reactive dog, we might imagine that this dog spent time in a rough playgroup as a puppy, and learned to associate other dogs with being bullied. Here, the cue is another dog, and the context is the room the playgroup was in.

The hippocampus: learning in context

One of the jobs of the hippocampus is to encode contexts. Those London cab drivers with oversized hippocampuses have countless contexts encoded to represent many different locations around London. The hippocampus of the puppy who had a tough time at playgroup encoded the room where playgroup happened as a context.

In the case of our laboratory rats, the hippocampus encodes the blue cage as one context and the purple cage as another. With a healthy hippocampus, the rat can differentiate between the two contexts, and is fearful of the cue only in the appropriate context. But with a damaged hippocampus, the rat can’t differentiate between the blue and the purple cage. Although he was trained that the bell only predicts a shock in the blue cage, he fears both cages, because his hippocampus is unable to properly represent the context of the blue cage.

The associative amygdala

One of the jobs of the amygdala, on the other hand, is to encode associations. It encodes the association between cue and stimulus (bell predicts shock) and between context and stimulus (the shock only happens in the context of the blue cage). When humans were tested with functional MRI to see which regions of their brain became more active during a fear conditioning trial, the amygdala and hippocampus responded in different situations. When humans were trained to associate a cue with a shock, their amygdala activated in response to the cue. When they were trained to associate only a context with a shock, both their amygdala and their hippocampus activated when they were exposed to that context. The amygdala activated in both cases because the association was being recalled in both cases, but the hippocampus was only activated when the particular context was recalled. Fascinatingly, this study also found that humans with larger hippocampus volume had greater fear responses in fear conditioning trials. There was no association between amygdala size and fear response.

Prefrontal cortex as mediator

We are not, thankfully, completely at the mercy of the whims of our hippocampus and amygdala, subject to uncontrollable fears based on past bad experiences. We have some ability to take a step back and calm ourselves down. One of the parts of the brain involved in this higher-order cognition is the prefrontal cortex (PFC). This region of the brain has direct connections to both the hippocampus and the amygdala and appears able to mediate some of the signals coming from those two regions. Functional MRI studies tell us that while fear acquisition involves the amygdala, fear extinction (learning to let go of a fear) involves the PFC as well. We also know that people who have thicker PFCs are better at extinguishing fear associations. This mediation by the PFC is what lets us take a deep breath and choose not to give in to our fears.

Do dogs have this ability to take a step back and try consciously to decrease their fears? Certainly they are not as good at this skill as humans are, but I wonder if they do have some ability to do this. In a recent post at Reactive Champion, a reactive dog owner describes a situation in which she believes her reactive dog did just that.

PTSD: failure to contextualize?

When this system goes wrong, how does it go wrong? One hypothesis suggests that post-traumatic stress disorder (PTSD) is a disease of failure to contextualize. Humans with PTSD report having flashbacks to previous trauma unexpectedly and uncontrollably, and in inappropriate contexts. If you were in a drugstore during a robbery, it would be appropriate for you to remember that traumatic event when you returned to that location, and even to feel trepidation about entering that store again. You’d probably think about the event a lot for the first days, weeks, perhaps months afterwards, in many other contexts, as well. But your brain should recover, and you should eventually come to not think of it constantly, and only be reminded of it in similar contexts, such as the same or similar locations.

People with PTSD, however, may have trouble limiting their recall of traumatic events to similar contexts, so that they may be retrieving these memories (often vividly) in any and all contexts, years after the trauma has passed. The problem may lie with their hippocampus, which may have difficulty limiting recall by context. And indeed, studies have shown that people with PTSD often have smaller sized hippocampuses compared to the healthy population.

The perspective of the reactive dog

On to the realm of pure speculation, then, because studies haven’t been done in hippocampus function in reactive dogs. But I think the story of the person involved in a trauma who can’t appropriately contextualize her memories is similar to the story of the dog who was involved in a trauma (dog attack, overwhelming experience in a crowded area as a puppy) and can’t contextualize the experience. A dog who is attacked by other dogs at a dog park may learn to fear the dog park, but if never attacked outside of the dog park, should he learn to fear all dogs, everywhere? I’d argue that that’s an inappropriate association for his brain to make, and that the mechanism of failure might have to do with a failure of the hippocampus to appropriately contextualize, just as in someone with PTSD.

I’m certainly not saying that all reactive dogs have PTSD, but I am speculating that the mechanisms might be similar. Does hippocampal function vary across a spectrum, with some individuals having high-functioning hippocampuses and others not so effective ones? Do dogs with hippocampuses on one end of that spectrum have difficulty limiting their negative associations, such that they are more likely to suffer from fearfulness and possibly fear aggression? I don’t know, and I don’t know if the research will ever be done, but it’s an intriguing story to consider.


  • Maren, Stephen, K. Luan Phan, and Israel Liberzon. "The contextual brain: implications for fear conditioning, extinction and psychopathology." Nature Reviews Neuroscience 14.6 (2013): 417-428. [PDF]
  • Feder, Adriana, Eric J. Nestler, and Dennis S. Charney. "Psychobiology and molecular genetics of resilience." Nature Reviews Neuroscience 10.6 (2009): 446-457. [HTML]