Why Dogs Bark and Lunge on the Leash

If I’d dig up all my clients’ files from the last 15 years, I bet half my dog book collection that on-leash aggression was the single most problem behavior owners hired me to help them with. On-leash aggression, or rather reactivity, is very common.
The typical explanation most laypeople, and some trainers, offer for the kind of barking and lunging that makes everyone’s head turn, frightens the targeted individual, and embarrasses the owner, is that the dog is protective, dominant, thinks he is in charge. It seems plausible: after all, the dog is moving forward, toward the target, and he is loud and threatening. However, “This is my space/mom/kid” - fill in the blanks – “get lost” is typically not the motivation that drives leash reactivity, and more enlightened dog pros know this.
If not dominance, what are the reasons for a dog flipping out? Well, there are several, rooted in following underlying emotions: fear, distress, excitement, frustration.

Failure to socialize, meaning that the pup didn't have enough exposure to a variety of environmental stimuli during the critical developmental stages, is generally blamed when a dog is fearful. Like the dominance angle, it makes a lot of sense to people and indeed, puppies raised in a bubble or in isolation can become neophobic: will fear and react to anything new. That is compounded when the odd novel encounter was unpleasant, and if the pup felt alone - didn't have a safe refuge zone and the loyalty of his owner.
But it is not just the unfamiliar that can cause dogs to overreact. Things known, but associated with discomfort, can provoke an undesired response as well.
Dogs make a blink assessment, based on their life experience, when presented with a stimulus.
Is it familiar?
Depending on the dog, if it is unfamiliar it is automatically perceived as a threat.
If it is familiar, does it announce: Pleasure? Or Discomfort? It is safe? Or not?
Whenever a dog anticipates discomfort, the stimulus is perceived as a threat; a threat to his safety, and that always causes distress. The barking, lunging and growling are the expressions, the symptoms of it.
Familiar stimuli are cues that predict a consequence, and dogs react to cues.

One might expect that dogs perceive other dogs generally as familiar. Shouldn’t a pooch identify another as a conspecific being? Innately “know” a dog as a dog?
Not necessarily: We have a vast variety of breeds that differ in structure and behavior, and if the pup only experienced his own, he might not recognize others as familiar, but as threats.
The other aspect to consider is that dogs to each other are providers: initially food, then entertainment, but also resource competitors. Dog-dog relationships can be complex, with each unfamiliar one a potential rival, and a familiar one a known rival, unless experienced otherwise. In my professional world, lunging and barking directed at dogs is more common than toward humans.

When a fearful dog barks and lunges, his motivation is to increase the distance, to drive the perceived threat away. Yet, many owners report that their pooch relaxes once he gets close enough to get a good sniff in. Why the obvious contradiction of wanting distance, but behaving better when it decreases? There is an explanation: Information reduces anxiety because it makes the unknown more familiar and predictable, and dogs’ preferred way to gather intelligence is through the nose. When there is no information forthcoming from the owner - information that, from the dog’s point of view, provides a copout, he has no choice but to get it from the other dog, and so he’ll attempt to get closer even though emotionally he wants him to disappear.

It is not always fear, though, why a dog acts out. Frustration plays a big role, and there are several reasons why a dog can be frustrated. One, again, has to do with information seeking.
Greeting rituals exist to find out more about a stranger while preventing and defusing potential conflict meetings. That is true with humans and dogs. When we shake hands, smile, bow or curtsy, and introduce ourselves, perhaps hand over a business card, the other understands that we don’t wish confrontation. Socially normal dogs first communicate from a distance: might raise or lower their bodies, lean back or forward, open their mouths or close it, lay back their ears, orient to the opponent directly or avert their eyes, and hold or wag their tails a certain way. Depending on the back-and-forth signals, at one point they might agree to sniff each other, typically in the head and/or anogenital region, to gather detailed information. Out-of-control barking, of course, isn’t part of normal greetings, but neither is being restricted from it. When the rather dense dude at the loop end of the leash prevents his pooch from behaving normally, perhaps even from communicating properly when he manipulates him with a head halter, frustration and its expressions result.
Fear is added to frustration if the dog is choke, prong, or worst of all, shock collar punished when he reacts; when he experiences pain for being curious, for wanting to communicate, for attempting to greet in a, for his species, appropriate way. In short, if a dog’s normal social behaviors and emotions are stifled with force, the stimulus, a dog or person, becomes a cue that triggers a stress response. Even if the consequence only happens sometimes, the dog will respond accordingly all the time.
Not only that, any detail that is part of an unpleasant event can become a cue, for example: the leash, the collar, the person who dished out the punishment, and the area where it happened.
When the leash in itself is an issue, the dog is already tense before the trigger even appears. Frenetic pulling and sniffing, and completely disconnecting from his person once outside, are common signs that the dog is distressed by virtue of being on the leash and/or outdoors.

Anything in a dog’s life that has a big impact leaves a big impression and provokes a big reaction in the future. If it is other dogs that were relevant events in the pooch’s history, he'll react whenever he sees/hears/smells another dog. Big deal suggests pressure and discomfort, but that is not always the case.
Dogs who repeatedly experience other dogs as primary facilitators of physical and mental entertainment, the ones who go to daycare or are chauffeured to the dog park and let loose once a day come to mind, have a certain expectation when they encounter a dog - any dog: fun and romping begins. If it doesn’t manifest because of the leash, or not quickly enough because the person who holds it is a slow-footed creature, the pooch, you guessed it, becomes frustrated, and the outburst can look very similar to the fearful dog’s, especially to a layperson.
And by the way, that kind of frustration, when something that’s expected doesn’t happen, is not reserved to people and dogs. During a “leave” exercise, a 12-week-old beagle pup soulfully bayed at me because he couldn’t access the treat I had tossed.

There is one more aspect that falls in the frustration compartment, and it is not fear or information seeking, and also not exactly play-motivated.
Some dogs, typically ones belonging to the herding group, have a heightened sensitivity to motion combined with an innate urge to control anything that moves. Steve White calls them: “Born with a badge on their chest”. These dogs have a strong natural drive to bring order back into the perceived chaos of animated dogs – or children, and become mighty agitated when the leash prevents them from doing their self-appointed job, but also often behave improperly when off the leash, at least from others’ point of view. Even though at times jokingly referred to as “fun police”,  some dogs and most humans have little tolerance for a pooch who stalks and chases; is locked, loaded and controlling. The bossy dog also doesn’t have much fun: He is easily overstimulated when presented with ongoing commotion in a busy dog park or daycare center, and overwhelmed with the task to organize and tone everyone down a few notches. A trained herding dog knows what to do and has the guidance of his handler - and is successful. A dog who has the drive but no training, the instinct but no clue, let loose on uncooperative other dogs and trailed by a yelling, irate owner, is not successful - and distressed as a result, and reactive on, but also off the leash.
On a little side note, the serious always-on-the-job dog can also be short-fused when another butts in while they work. In that context, the ball fetching Border collie who snaps at a space-encroaching retriever is not resource guarding, but annoyed by the interruption. I recently had an Australian cattle dog client where that was clearly the case. Believed to be dominant and aggressive, she was simply so focused on her human and what he had in his hand, and if he might throw it, that anybody who'd pop in her face got a sharp and clear: "Buzz Off!" Unfortunately, in an dog park or off-leash trail, it is exactly that kind of focus that gets other dogs' attention and provokes them to "check out what that dog is so interested in".

Frustrating situations make dogs irritable and pumped, and when confronted regularly with the triggers, the cues, they become sensitized: have a heightened sensitivity to predictors, motion and sound, probably also scent, and act more and more out of control from greater and greater distances. The collar and leash, because of the restraint and discomfort they represents, amplify the problem.
The question one must ask when a dog barks and lunges is what he expects to happen next. Play? A job? Emotional discomfort? Physical pain? That expectation is based on the dog’s experience, and is what dictates future behavior. Expectation dictates behavior.
I bet what you all want to know next is what to do about it. I will tell you – in the next post, but I’ll give you a hint right now: neither clipping the leash off, nor allowing yourself being pulled closer to the trigger, is it. Oh, and commanding the dog in a sit position and coercing him to watch you isn’t it either.