Causes of Reactive Dog Behavior and How to Train Accordingly

Dealing with dogs who “go off” or “lose it” in certain circumstances.


by Pat Miller

About 85 percent of the time, my Scottish Terrier, Dubhy (pronounced Duffy) is laid-back and phlegmatic. He methodically solves every training challenge I give him (although I don’t expect him to break any speed records on the agility course). His low-key approach to life won our hearts and earned him a permanent home after we found him running loose in a Chattanooga neighborhood in January of 2001 at the tender age of six months. Residents said he had been roaming the area for at least six weeks; a search for his owners proved fruitless. His uneventful introduction to the rest of our pack sealed his fate, and Dubhy joined the Miller family.

Thus his behavior at a Tennessee trainers’ meeting some 16 months later came as a complete shock to me. I arrived early at the Knoxville location, and was sitting on the far side of the training room when fellow trainer Claire Moxim entered with her Labrador Retriever, Pete. Dubhy knew Pete well; they had played happily together at my training center on several occasions.

Dubhy looked up as Claire and Pete entered, then went nuclear, raging and snarling at the end of his leash.

My trainer brain immediately leaped to the obvious “restraint frustration-aggression” conclusion. Here was a dog that Dubhy knew from prior positive play experiences. Dubhy was excited to see Pete, and his frustration at not being able to greet his friend was manifested in a display of aggression. Or so I thought.

“Let’s have them meet on loose leashes,” I suggested to Claire. “Once Dubhy gets to say hi to his pal, he should be okay.”

Fat chance. As Dubhy and I approached Pete on a loose leash, Dubhy did, indeed, seem to settle down. I mistook his controlled behavior for calm behavior. As we came near the big black dog, Dubhy redoubled his hostilities. When I reached down and touched my dog’s hip in an attempt to interrupt his attack, he whirled around and punctured my hand with his teeth in a classic display of redirected aggression. Yikes! Overnight, seemingly without warning, Dubhy had turned into a reactive dog.

Talkin’ ’bout excitation
“Reactive” is a term gaining popularity in dog training circles – but what is it, exactly? In her book Clinical Behavioral Medicine for Small Animals, Applied Animal Behaviorist Karen Overall, M.A., V.M.D., Ph.D., uses the term to describe animals who respond to normal stimuli with an abnormal (higher-than-normal) level of intensity. The behaviors she uses to ascertain reactivity (or arousal) are:

• Alertness (hypervigilence)
• Restlessness (motor activity)
• Vocalization (whining, barking, howling)
• Systemic effects (vomiting, urination, defecation)
• Displacement or stereotypic behaviors (spinning, tail- or shadow-chasing)
• Changes in content or quantity of solicitous behaviors

The key to Dr. Overall’s definition is the word “abnormal.” Lots of dogs get excited when their owners come home, when they see other dogs, when a cat walks by the window, when someone knocks at the door, and so on. The reactive dog doesn’t just get excited; he spins out of control to a degree that can harm himself or others around him. In his maniacal response to the stimulus that has set him off, he is oblivious to anyone’s efforts to intercede. He goes nuclear.

Dubhy has demonstrated reactive behavior in other situations as well. Our neighbor’s black and white cat, Barney, has appointed himself Official Rat Patrol in our barn. Barney’s casual strolls outside our fence send our Scottie into a frenzy; Dubhy runs the fence line like a maniac, barking hysterically and doing stereotypic spins at each corner. When I place myself in Dubhy’s path and wave liver treats in his face I might as well be invisible; he darts around me and continues on his mission. If I let him, he would run himself into heat stroke.

Causes of reactive behavior
There is definitely a genetic component to Dubhy’s out-of-control level of excitation. If I had researched Scottish Terriers before I decided to keep him, I would have learned that this behavior is actually a desired trait for that breed (see sidebar).

The excuse is that good breeding maintains the original temperament and behaviors of purpose-bred dogs. Labrador Retrievers should be able to retrieve ducks, for example, Border Collies should be able to herd sheep, and Scotties and other terriers should display the pugnacious behavior that makes them good vermin-killers. I had heard this all my life, and was quite familiar with the terrier reputation for feistiness. I now have an intimate understanding of what that really means.

As with most behaviors, environment also plays a role in the responses of reactive dogs. With careful handling, a dog with reactive tendencies may never exhibit the abnormally intense reaction to stimuli that lies dormant in his genes. A dog who could have been a reasonably self-controlled canine in normal conditions, might be induced into reactivity if kept in a highly stimulating environment.

Had I been smarter and realized Dubhy’s propensities earlier, I might not have taken him to doggie daycare, where he experienced a heightened level of stimulation in the presence of other dogs that might have contributed to his Jekyll and Hyde reaction to Pete. He might never have been able to “play well with others,” which he did nicely for over a year, but we might also have avoided the “can’t even control himself in the presence of other dogs” behavior that I found myself dealing with in Knoxville.

Managing reactive behavior
Even if you have a highly reactive dog, all is not lost. A reactive dog may be a challenge, but there are things you can do that will help you cope with the stress of living with a dog who tends to flip out. Let’s start with management:

1. Identify his triggers. Make a complete list of all the environmental stimuli that set off your dog’s nuclear reactions. Be specific. For Dubhy that would be: A) the neighbor’s cat flaunting himself on the other side of the fence; and B) some other dogs – mostly those who are taller than Dubhy. Since I can’t successfully predict which dogs will set Dubhy off, I assume all dogs will, and act accordingly.

2. Prevent his access to the stimuli. Change your dog’s environment so his reactive behavior isn’t frequently triggered. For example, you can block his visual access with barriers, control it with training tools, or simply move your dog to another environment when the stimulus is likely to be present.

For Dubhy that might mean: A) asking the neighbor to keep his cat home (which probably won’t happen), or erecting a solid wood privacy fence so Dubhy can’t see the cat, and B) using a head halter when I walk Dubhy in public so I can easily turn him away from other dogs, breaking the visual contact that triggers his reactive behavior.

Modifying reactive behavior
If you are particularly successful at managing your dog’s environment, that may be all you need to do. Lots of dog owners get by on management without ever retraining the dog. If, however, you’d prefer to change your dog’s behaviors in case your precautions should slip, or if you’d like to be able to relax when you take him out, you can learn to put a behavior modification program in place.

The most powerful tools you can use to reprogram your dog’s reactive responses are classical and operant conditioning. Don’t be frightened off by the technical terms; these behavior modification tools are easy to put into practice.

Say your dog is reactive to people walking their dogs past your house when she is inside, and she barks hysterically and scratches at the windows whenever she sees a dog walking past. You can manage the behavior by closing your drapes, moving the sofa to the other side of the room so she can’t jump up and see out, or putting up a baby gate to prevent her access to the front room. But if you really like having the drapes open, the sofa fits perfectly under the front window, and you enjoy your dog’s company when you are watching TV, you might be more motivated to undertake a behavior modification program to change your dog’s annoying response for the long term.

Think of it this way: There’s a little switch in your dog’s brain that gets flipped whenever she sees a dog outside your window. She likely sees each dog-human pair as a trespassing threat. The instant one appears, her brain kicks into overdrive and she goes nuclear. This is a classically conditioned behavior. She is not thinking, “If I bark hysterically and run in circles, climb the walls and claw the curtains, something good might happen.” Her brain is screaming, “Alert! Alert! Intruders!” and her body reacts accordingly.

Of course, her behavior is reinforced by the fact that every time she does this, the intruders leave. Her canine brain doesn’t comprehend that they would’ve left anyway; she may well think she made it happen. This negative reinforcement (the dog’s behavior made a bad thing go away) only increases the likelihood that the behavior will continue, or even escalate.

This is operant conditioning. In reality, classical and operant conditioning work together all the time to mold our dogs’ behaviors. We use food to operantly condition our dogs to respond to our cues with a desired behavior. At the same time we give our dogs a very positive classical association with the whole training experience because they love food (and playing with us), so they come to love training, too.

To change your dog’s classical association with the presence of a dog walking by from negative to positive, you need to convince her brain (the automatic response part, not the thinking part) that the presence of dogs walking by makes something wonderful happen. This is called counter-conditioning.

Build an unconscious positive association
To succeed at counter-conditioning, begin by preventing your dog’s access to the windows when you are not there so she can’t practice the undesirable behavior. Plan your training sessions for a time of day when you’ll have high traffic past your window. If there is no such time, convince several of your dog-friends to leash their canine companions and – at different times – march back and forth past your window for 15 to 20 minutes. You can take them all out to dinner afterward as a reward!

Be sure your friends know they need to march out of sight in each direction before they turn around. Mark the place on the sidewalk where you want them to turn, just to be sure.

Meanwhile, back at the house, have your dog on leash, using a head halter if necessary. As soon as the marchers come into view, start feeding your dog something totally irresistible, such as tiny morsels of canned chicken. Be sure your dog has noticed the pair before you begin feeding, but don’t wait for her to work herself up into a frenzy. The instant she notices them, begin feeding her. Feed the morsels nonstop as long as the marchers are in view – treats raining from the heavens! As soon as the dog and human passersby are gone, stop feeding your dog. When they reappear and your dog notices them, start feeding her again.

Your goal is to convince your dog that a dog walking by makes chicken happen. You will know you’re making progress when you see your dog notice the walkers and, instead of getting tense and barking, she turns to you with a smile and a “Where’s my chicken?” expression. When she realizes that chicken only happens in the presence of a dog outside the window, she’ll want them to be there, rather than wanting to chase them away.

Build a conscious positive association
When you have successfully changed your dog’s automatic or unconscious association with the stimulus, you can start using operant conditioning to teach her that the presence of the previously offensive stimulus is a cue to sit and look at you.

It’s easier than you might think; just ask her to sit when she gives you the “Where’s my chicken?” look, before you feed her a treat. Slow your rate of reinforcement (how fast you feed treats), and reward her only for the desired behavior, rather than shoveling treats nonstop.

Eventually you can fade the verbal “sit” cue; the mere appearance of a dog walking by your house will become the operant cue for your dog to sit and look at you.

All is calm
Counter-conditioning is definitely more challenging with a reactive dog than with one who responds to stimuli with a normal level of intensity. It may take you longer than it would with a “normal” dog, but it does work. Don’t give up! The more you can saturate the reactive dog’s environment with the concept of “calm,” the more successful you will be at managing and modifying her nuclear reactions.

Help your dog understand that calm behavior is universally rewarded (see “Practiced Calm,” WDJ February 2002). Keep your own interactions with her calm and cool, even when you are tempted to scream at her to startle her out of the high-intensity behavior pattern. Your own intense behaviors are more likely to elevate her energy level than tone it down.

Learn about calming massage, acupressure, and T-Touch™ techniques to help your dog relax. Research herbal, homeopathic, and flower essence remedies to see which ones might be appropriate for your dog. (You may need a holistic veterinarian to help you with this; go to the Web site of the American Holistic Veterinary Medical Association at for a directory of holistic vets in the United States, listed by state, to find one near you.)

It is possible to make progress with a reactive dog. While my Scottie is not yet ready to show off his piano-playing technique at the next big dog trainer conference I attend, I am much more comfortable taking him to relatively small gatherings where other dogs might be present.

We recently helped staff a booth at a fair. Our two-hour stint was uneventful despite dozens of dogs walking by on leash – except for the bad moment when a thoughtless lady allowed her dog to run 25 feet to the end of her retractable leash and get right in Dubhy’s face. I did a quick about-turn with Dubhy to avoid disaster and a setback to his modification program, and then proceeded to explain to the lady why retractable leashes weren’t a good idea in a crowd. She was offended and indignant. I was just thrilled that Dubhy had come so far with his reactive behavior.

-Pat Miller, WDJ’s Training Editor, is a Certified Pet Dog Trainer, and president of the Board of Directors of the Association of Pet Dog Trainers. She is also the author of The Power of Positive Dog Training, and the just-released book Positive Perspectives: Love Your Dog, Train Your Dog.


    • Good point, John. I’ve been checking the danglers of every dog I meet and haven’t found a one. Maybe breeders could figure out some way to get peenies on a dog?! 😉

  1. I feel like a failure. A bluff! My dog when walking with me is a lunatic- he has a loud and alarming bark and thrashes about like a fish out of water when I walk him. He reacts to other dogs – wants to greet and play but his behaviour is disarming to other dog owners and I fear he will be attacked for his overzealous displays…. I want to call out “he’s a rescue” to see if I’ll get more understanding from pet owners…. the problem is…. when he walks with the trainer we’ve hired he is a complete angel! I could cry – my trainer walks the dog I want …… I walk a dog that goes off his head… Why? How can I change this?

    • Hi Jacki! A great trainer needs to be able to teach you how to handle your dog and not walk the dog for you.
      The trainer is more experienced and doesn’t share the same emotions you do. The energy you have will transfer to your dog. Walk the dog like your the leader, practice the skills the trainer has taught you in the house so you both can get practice on what to do. The dog shouldn’t be close enough to another dog to react at this point. You may need to start 100 feet out to practice the above technique. If the dog is reacting, your too close to the stimulus and have lost the ability to train in that moment.

  2. Ugh! When we adopted our lab Pitty mix 8 months ago she was an angel with my family’s older dog for a bit, but after a month or two they started to have fights on the daily. We soon realized my dog (The pitty Lab) is Toy aggressive and my family’s other dog is Food aggressive, so we tried to take away food and toys when they are together but they always get into fights still and now their in separate yards so they cant get to each other.

  3. I’ve had Newfoundlands for almost 25 years. I was trained by a trainer with my first and have trained the rest myself. My last few have been rescues. I have an 8 year old Landseer male who might be what is classified as “Reactive”. He came to us 3 years ago, from a lovely family, but never had direction. It sounded like he dominated their other newf and them. I quickly noticed he did not like my other dogs playing and would run into them to break them up. He did not like my daughter running around. He would lunge at the other dogs while waiting for food. He would lunge at my daughter when she went upstairs, going out the door to go outside, if she was playing with friends, etc. At first I thought he might be aggressive but quickly realized he needed direction. I was able to work with him and train him not to react to most. I always notice that he doesn’t carry himself in a dominant, noble, confident way. He reacts quickly without thinking. His tail is down between his legs a lot. He is very needy for affection, though I dont allow him to be pushy about it.
    The one thing I cannot break him of is his reaction to when our dogs play. He doesn’t like it and feels he needs to stop it. I don’t know why he reacts this way. I know his breeder well. She is a highly reputable breeder who did not experience that with him as a puppy. It has gotten to the point where my other dog wont play if he is around. My niece’s dog is visiting and loves to play, but wont because of how Boo reacts.
    Any ideas on how to work with this would be greatly appreciated!

  4. Thanks! My parents got a five-year old Jack Russel Terrier / Shih Tzu mix from a shelter and she displays the most reactive behavior I have ever seen. Whenever she sees another dog outside (even from a 100 meter distance), she starts to squeal like a slaughtered pig. Not only does this make everyone in the vicinity stare at you, it also triggers aggressive behavior from the confronted dogs. Socializing her seems to make things worse. The more people/dogs there are around her, the more aggressive she becomes. She also doesn’t care about treats or food in general, which makes it more difficult to train her.
    After reading this article, I decided she might just be scared so I now pick her up whenever I see a dog approaching and cover her eyes. And like magic, it works 🙂 It’s also clear now that her behavior is the result of fear. She is apparently terrified of dogs she doesn’t know, my assumption is that she was attacked by another dog at some point in her life.

  5. My foster is a pit mix that the group had fixed. She was found as a stray who had a liter somewhere but there were no puppies found. She was boarded in a kennel before I started fostering her. She is very sweet but chews EVERYTHING, including myself! I got her a kong and other food release toys and take her on walks daily but as soon as we begin to play she gets excited and starts jumping up on me “nipping” me. How should I stop this? My arms are in bad shape due to this nipping (and I’m old). Any suggestions would be appreciated. Even when I stopped playing with her outside she will get “hyper” and start to nip me while watching TV.

    • Hi Susan! My parents dog does this when he gets excited to play, he nips me because he is just excited and has too much energy! I know how you feel! Is daycare a possibility? Maybe some socialization and getting some energy out once or twice a week would help?

  6. Thank you so much for this article, I really needed it today.
    I adopted my dog at “8 months old” from a local rescue who transported him from Northern Canada. He’s a collie cross who was in pretty rough shape. I obviously got in over my head due to a 6 month ordeal of severe separation anxiety, escape artist tendencies, and some serious behavioral issues. He was terrified of ALL people, dogs, and objects. I poured my heart and soul into this dog by way of vet visits, CBD oil, obedience training, private lessons, multiple dog psychology books and I even started taking him to herd sheep to help him find his confidence. We built a custom kennel and erected the tallest dog proof fence in the neighborhood. There have been many hurdles, mainly, a visit from animal control but we have made HUGE progress. It’s been fourteen months now and he is a dream dog. We even tackled the holy grail of dog training: loose leash walking! (Thank you gentle leader!!!)
    However, we are still working on dog reactivity (just strange dogs- he gets along amazingly with our friend’s dogs who he has been properly introduced to). The worst part is how clueless everyone is. Your article resonated with me because it is hard owning a dog who is reactive. Especially around people who are so blissfully ignorant. I want to kick every person in the shins who lets their dogs bound from their car in a dog on-leash area to run full tilt toward my on-leash and under control dog. I’ve been screamed at, told my dog is aggressive or just ignored. I am just trying to live my life with my amazing dog who just needs tons of love, more space and a proper introduction. I wish every dog owner understood dog reactivity.

    • Great to read. We got a collie pup at 11 a during lockdown and she is so reactive to everyone and every dog that we can’t take her out. So great to hear it is possible to help her change this behaviour.

    • Thank you for your comments. It makes me feel better, as we adopted a wonderful GSD/Pit mix about 9 months ago, and he has had several of the issues you described, but with work he has made such progress and is nearly there! He is almost perfect in the house, and just fine with dogs he knows, but is still fairly reactive with some strange dogs, and absolutely FREAKS out when he encounters a cat. A squirrel is nearly as bad. I do see that many owners just don’t care, and just let their dogs run up or approach, etc.

  7. Lou, I have a very reactive dog too and I bought her a vest which says “no dogs” (even though she is fine with some). It keeps people from bringing dogs up to her. Prior to this she had one that said “in training – please give me space” … might be something to consider…

  8. My rescue dog is so reactive that she has pulled me down trying to get at other dogs. I have to walk her where I know there is something vertical to grab (street pole, fence, etc.). She starts out with a whine, then leaps up, all four feet in the air, screams, and lunges. It is horrible. I hired a trainer who gave me a chain (not prong) collar to sit high up on her neck behind her ears, and her her back when she starts getting reactive. Walking her is a terror, always watching for dogs, cats, squirrels. She is one year old, and I have had her for 3 months. I want to make this work, but am being encouraged by those who have seen her in action to bring her back to the rescue group. Is there any hope or will her reactivity always be something that I must fear?


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