"Bared Teeth, Raised Hackles & the Myth of Aggressive Intent."

Signals of Aggressive Intent? Or Autonomic Reflexes?

Originally published in slightly different form on August 31, 2009 at PsychologyToday.com.

The Least Understood of Animals?

Dogs are the most talked about and yet the least understood of all animals.

From what I’ve observed, one of the biggest roadblocks to truly understanding a dog’s nature—as neither Machiavellian power-schemer always intent on being alpha, nor emotionless Skinner-box automaton—is the tendency by many in scientific and academic circles to blithely ignore three simple rules whenever discussing canine behavior:

Ockham’s razor, [1] Morgan’s canon, [2] and the rule against anthropomorphism.[3] All three rules demand that we always look for the simplest explanation for a phenomenon, as long as it satisfactorily explains all aspects of it.

One glaring example of the way scientists and scholars have contributed to some of the most common misconceptions about dogs, is that in many textbooks on behavior you’ll read that a wolf or dog will raise its hackles “to make its body appear larger to other animals.” This is also (supposedly) why a cat arches its back, why a bear rises up on its hind legs, etc. The most widely-accepted explanation of these phenomena is that these animals intentionally produce these behaviors to make themselves look bigger to their foes. And it breaks all three of our simple rules.

Build Up of Static Electricity?

I don’t know much about cats and bears; I’m a dog trainer. But what I do know is that the hackles aren’t under a dog’s conscious control. They’re raised automatically when the dog is fearful but has no way to release the energy generated by his nervous system; in fact this “behavior” may be nothing more than a build-up of static electricity! We can’t consciously control our goose pimples, so why suppose a dog can control his hackles? That goes beyond anthropomorphism and gives dogs abilities that not even humans possess.

Secondly, even if a dog could control the muscles that make his hairs stand on end, unless he first knows what he looks like to himself (which would require a sense of self and maybe the ability to recognize his own image in a mirror [4] how could he try to make himself look “different?”

Thirdly, without the use of language and internal narrative, how could a dog be able to differentiate one category or state of being from another, i.e., smaller from larger? “Before my teacher came to me,” Helen Keller wrote in 1908, “I lived in a world that was a no-world. I cannot hope to describe adequately that unconscious time of nothingness. Since I had no power of thought, I did not compare one mental state with another.” [5] (You can’t compare things unless you can first put a handle on them.)

Fourthly, without a full-blown theory of mind [6]—the ability to attribute mental and emotional states to other beings—a dog can’t possibly know what the other dog would think or feel about seeing him get suddenly bigger, so he could have no “reason” for producing this behavior.

Finally, I’ve seen a dog’s hackles go up when he comes up behind a horse, for example. If the horse has his back to the dog, why would the dog bother to “make himself appear larger” to the horse’s rear end? I’ve also seen dogs whose back hairs stand on end when they see another dog, and yet his hackles sometimes stay up even when he goes around behind the other dog to sniff its butt.

Some Scientists Believe Dogs Are Thinking in Some Very Complex Ways!

Perhaps mine is only a semantic quarrel. I don’t know for certain that those who’ve written about this phenomenon actually believe it takes place under the dog’s conscious control, or that the dog really intends to make himself appear larger to others, etc. But there is implicit within this explanation a host of problems that give us the impression that dogs are thinking all these things through, in some very complex ways, when it’s far more likely that this simple “behavior,” which is almost purely reflexive, is the result of a surge of nervous energy.

Does this mean that raised hackles aren’t evidence that a dog is feeling aggressive? Not at all. It just means that he’s not capable of intentionally raising his hackles or forming the intent to communicate whatever feelings he might have to anyone else, not even to himself.

How about the idea that dogs bare intentionally bare their teeth?

Here we come up again the same sorts of problems. And just like before, they all add up to the necessities of the dog having a sense of self and other, to know what he looks like, an ability to form intent (which dogs don’t have), and a fully-developed theory of mind.

Wait, go back. Don’t sneak that thing about intent in between parentheses. Who says dogs don’t have the ability to form intent?

To me, intent requires conscious thought. [7] Conscious thought requires the use of language in the form of an internal narrative. Plus intent also requires a form of mental time travel, where the dog projects the results of an intended behavior into the future and predicts what the outcome might, hopefully, be. Dogs live in the moment. They don’t time travel.

So why does a dog curl his lips back?

Snarling Is an Autonomic Reflex

Technically speaking, he doesn’t. Again, if we look for the simplest explanation, one that also explains all aspects of the phenomenon, we can see that the lip snarl is just another autonomic reflex, not an intentional act; when a dog has a strong urge to bite, with a lot of emotional force behind it, his lips curl back involuntarily to get out of the way of the teeth. It’s an important—yet purely unconscious—mechanism designed by nature to prevent the dog’s lips from being damaged or punctured by his own teeth when he bites something (or someone).

For example, many dogs curl their lips back when you give them a bone or a toy. Who are they communicating their aggressive intent to? The toy? The bone? Yet if the behavior is a simple reflex, designed to get the lips out of the way of the dog’s teeth, it makes perfect sense.

My dog Fred once had an encounter with a dog who, according to her owner, hated Dalmatians. The two dogs were walking parallel to one another on wide stretch of sidewalk. Fred skirted ahead of the aggressor, who was barking frantically, but whose lips weren’t curled back and whose hackles weren’t up. However, as soon as Fred’s back was turned, the instant he could no longer see her, her lips did curl back. If she did it to show “aggressive intent,” she was very mixed up. [8]

Finally I knew a pit bull named Augie Doggie who seemed to lack this lip-curling reflex. As a result he kept biting through his own lips whenever he went to chew a toy or a stick. His owner had to be very careful about keeping people from giving Augie Doggie things to chew because Augie Daddy couldn’t afford to pay for all the stitches his poor dog had to keep getting in those big fat lips of his.

How Emotion Moves Through a Dog's Body

If we take a step back, away from the literature, and just look at these two simple reflexive behaviors, and follow Ockham’s razor, Morgan’s canon, and the rule against anthropomorphism, and we really think this through, whittling away all the nonsense, we can see that both behaviors are the result of how emotion moves through a dog’s system in the form of emotional and electrical energy, and that the internal, unconscious intelligence of the dog’s own body is responsible for the behavior; it’s not created intentionally from within the dog’s mind.

My hope, vain though it may be, is that in the future, all scientists and scholars, when describing canine behavior, will use our 3 simple rules, that textbooks will be re-written (there’s a vain hope!) so that the phrases “the dog raises its hackles” will be replaced with “the dog’s hackles go up,” and “the dog bares its teeth” will be replaced by “the dog’s lips curl back.” I also think we should systematically replace “intent” with “desire,” whenever and wherever we can. Once we remove these hidden signals, subtly encouraging us to anthropomorphize our dogs, we may start to see them more clearly and understand them a lot better.

Dogs are amazing animals. At times they really do seem smart enough for us to ascribe higher levels of thought to the kinds of things their social and emotional intelligence enable them to do. But my feeling is the better we understand them for who they really are, the better off we’ll both be, canine and human.


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1) Ockham’s razor: A scientific principle stated by William of Ockham (1285-1347/49), a scholastic monk, that “Plurality should not be posited without necessity.” The principle gives precedence to simplicity; of two competing theories, the simplest explanation of an entity is to be preferred. The principle is also expressed “Entities are not to be multiplied beyond necessity.”

2) Morgan’s canon: First stated by Lloyd Morgan in 1894, that animal behavior should never be attributed to a higher mental function if the behavior can be satisfactorily explained in terms of a simpler cognitive process.

3) My take on anthropomorphism: “How Dogs Think: The Debate Between Emotion and Logic.”

4) Your aunt’s dog may cavort in front of a mirror, but that doesn’t mean that she recognizes her form as being exclusively hers. There’s a specific way of determining if animals can recognize their own forms, called the mirror test, and no dog has ever passed it. In fact, even the mirror test is flawed. There are many fully functioning adult humans, living in other cultures, who are unable to pass the test!

5) Helen Keller also once said, “College isn’t the place to go for ideas.”

6) Theory of Mind

7) Forming an intent to do something is quite different from having a desire to do it. In humans, a desire may lead to conscious intent; the same can’t be said for dogs.

8) This is when I first realized that dogs don’t “bare their teeth;” that the behavior is an unconscious reflex. The reason the dogs lips curled back is probably because while she and Freddie were on equal terms, and his head (with its teeth) was facing her, her urge to bite was held in abeyance. But once Freddie’s back was turned, the urge to bite came on in full force, which is what caused her lips to curl back, out of the way of her teeth.

After I’d formed that realization I began to remember the way Fred and other dogs took their toys, as if snarling at the inanimate objects. It was only several years later that I came across a dog—Augie Doggie—who seemed to lack this natural reflex.

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