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A dog barking and lunging at the end of their leash is an all-too-common occurrence. No doubt you’ve seen a dog like that in your neighborhood, or perhaps your own dog exhibits this disturbing behavior. But do you understand what’s motivating your dog? Are they frustrated, scared, or out to do harm? It’s tempting to label these outbursts as aggression, but it’s not that simple. Dogs that act out of proportion to the situation, such as barking hysterically at a dog on the other side of the fence, are exhibiting reactivity. Although reactivity can lead to aggression, it’s important to understand the difference between these two behaviors.

What Is Dog Reactivity?

Dogs who respond to normal, common occurrences with abnormal and excessive levels of arousal are often termed reactive. For example, seeing a stranger on a walk is an everyday occurrence for most dogs and, depending on the dog’s personality, may elicit no interest at all, a passing glance, or a friendly desire to approach. However, for a reactive dog, the sight of a stranger can lead to intense barking, lunging, cowering, pulling on the leash, and so on – behaviors out of proportion to the situation.

These dogs are overcome by whatever emotions a particular trigger has elicited and therefore find it hard to calm down or listen to their owner. If you’ve ever tried to walk a reactive dog, you’ll understand how challenging it is once they’ve been set off. Loose leash walking and good manners go out the window, and it’s all you can do to drag your dog away.

Yellow Labrador retriever puppy barking outdoors.
© Christine Glade via Getty Images

What Causes Reactivity?

Although fear is a common motivator for reactive dogs, there might be a different underlying emotion, such as frustration or excitement. The important point is that a reactive dog responds faster and more intensely than a non-reactive dog. Rachel Lane, M.Sc., CBCC-KA, CPDT-KA, is the owner of Leash & Learn dog training and a certified canine behavior consultant with her master’s degree in applied animal behavior and welfare. She reminds people that reactivity can happen anywhere – on-leash, off-leash, indoors, and outdoors.

Dogs that become frustrated when their excitement to greet another dog or a stranger is thwarted by a leash, fence, or other barrier often lack emotional self-control. On the other hand, anxious dogs are often reactive due to a lack of socialization while they were a puppy. Things that would be no big deal to other dogs are overwhelming instead. Or a previous bad encounter, such as being attacked by another dog, can create fear later in life. Lane points out, “It is important to keep in mind that the threat a dog is reacting to may not be scary for the person on the other end of the leash. The threat simply has to be scary for the dog for them to display reactive behavior.”

What Is Aggression in Dogs?

Aggression can be characterized as any threatening or harmful behavior intended to avoid escalation of conflict, to increase distance between the dog and the target, or to cause damage to the target. Although aggression can lead to biting or the surrender or euthanasia of the dog, it’s a normal dog behavior which, depending on the context, can be adaptive or appropriate. If your dog attacked an intruder, for example, you would likely label them as courageous and loyal, but their behavior was aggressive, nonetheless.

According to Lane, “Aggression is a part of a dog’s natural and normal behavioral repertoire and has multiple causes. People often consider aggression socially unacceptable, but all dogs are/can be aggressive. Like any behavior trait, aggression is a complex interplay of genetic and environmental factors.”

©mikhailgrytsiv -

What Causes Dog Aggression?

Because fear is the most common cause of dog aggression, most cases involve dogs trying to put distance between themselves and the target. However, dogs can be aggressive for many other reasons. Some of these include the following:

  • Maternal aggression, where a mother dog is overly protective of her puppies.
  • Resource guarding where the dog defends items of perceived value like bones or toys.
  • Territorial aggression where the dog protects what they see as their domain, such as the backyard or the car.
  • Protective aggression, where the dog guards a human such as their owner.
  • Pain aggression, where a dog experiencing discomfort defends against any touch or movement that might intensify that pain.

Aggression may vary depending on a dog’s age, breed, size, and home dynamic. A recent study of aggressive behavior published in the journal Scientific Reports looked at thousands of dogs in Finland. The researchers found that older dogs, male dogs, small dogs, and dogs that lacked the company of other dogs all showed an increase probability of aggression toward people. The same was true of dogs with novice owners and those with fearful personalities. Finally, certain breeds like Collies (rough), Toy Poodles, and Miniature Schnauzers had higher odds of aggressive behavior than other breeds like Labrador Retrievers, Golden Retrievers, and Lapponian Herders.

Can Dog Reactivity Lead to Aggression?

So, dog reactivity involves out-of-proportion emotional arousal, and aggression involves conflict and harm. But is there any relationship between the two behaviors? Yes. Reactive dogs can become aggressive depending on the situation and past experience. First, reactivity puts a dog at high risk of acting aggressively because they’re in a heightened emotional state which shuts down the thinking parts of the brain. A reactive dog is more likely to behave instinctively with fight, flight, or freeze than to consider their actions.

German Shepherd puppies wrestling in the grass.
©Kate -

Second, reactive dogs, particularly those with fear-based reactivity, can learn that aggression gets results. For example, if they growl at a stranger and the growl is ignored, the dog learns to escalate to snapping and biting, which drives the stranger away. Lane says the goal of reactive behavior is often to increase the distance between the dog and the perceived threat. “It is important to note that while a dog may currently be performing reactive behaviors and has never injured another person or dog, these behaviors can morph into defensive aggression. This change can happen over a period of time, such as after the dog’s many attempts to create distance between themselves and a stimulus have repeatedly failed. Or a dog’s behavior may escalate during one single interaction with another individual,” she says.

How to Handle Dog Reactivity?

Reactivity is distressing for your dog. And because it can lead to aggression, it’s important to try to prevent it in the first place. Socialize your dog, positively expose them to as many situations and people as possible, and teach them to control their emotions. But if your dog has already developed reactivity, Lane warns, “There are no quick fixes. An owner’s participation, consistency, and follow-through all play a critical role in a successful behavior modification plan.”

Lane says that any behavior change in your dog could potentially have a medical cause, so her recommendation is to first rule out health issues with your veterinarian. Next, she counsels seeking out the help of a qualified professional such as a certified behavior consultant or veterinary behaviorist. Then she advises a three-step program, which includes the following:

  1. Practice management. Avoid situations that emotionally arouse your dog, whether that means walking at night when it’s quiet or staying away from the busy park. Whatever it takes to prevent your dog from reacting to their triggers.
  2. Begin a positive-reinforcement training program. That might include behavior modification protocols like desensitization and counterconditioning or teaching your dog an incompatible behavior. For example, instead of staring at a dog in the distance, your dog can look at you.
  3. Learn to read dog body language. If you catch subtle signs, like lip-licking or pinning back the ears, that indicate your dog’s emotions are shifting, you can intervene before your dog becomes reactive.

A possible fourth step involves medication, which can help calm your dog and therefore make them more receptive to learning new behavior patterns. By following this program, in time your dog will form new emotional associations with their triggers and their reactivity will diminish.

Related article: Cues to Teach Your Dog to Avoid Approaching Dogs
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