The Dark Side of Socialization: Fear Periods and Single Event Learning

The Dark Side of Socialization: Fear Periods and Single Event Learning

Years ago, when I was a senior veterinary student working as an extern with OSU’s clinical behavior service, I saw a case that stuck hard in my memory and has never faded.

The patient was a beautiful three-year-old female German shepherd I’ll call Heidi.  She was a lovely dog in most respects – friendly and gentle with people, very bright, and a quick learner.  In the consultation room, she was calm and well-mannered, approaching us readily with a wagging tail for petting and treats.

Heidi had one flaw, and unfortunately it was a serious one – she was intensely, violently aggressive towards other dogs.  She had to be brought in to the veterinary hospital through a rear entrance to avoid walking her through the lobby, and great care had to be taken to make sure she did not encounter any other dogs on her way in or out of the building.  Her owner was a petite middle-aged woman, who loved Heidi dearly and was deeply committed to her.  She had been managing Heidi’s dog aggression as best she could for a long time, but things were getting worse.

The incident that finally prompted her to seek out a veterinary behaviorist had occurred the week prior to her visit with us.  A smaller, off-leash dog belonging to a neighbor in her apartment complex had approached her and Heidi during their daily walk.  She tried to pull Heidi with her and hurry away in the opposite direction, but the other dog began running towards them and Heidi was frantic to get at it, lunging and snarling at the end of her leash.  In desperation, her owner tackled Heidi and lay on top of her, using her body weight to keep her thrashing 80 pound dog pinned to the ground until the other dog was retrieved safely by a neighbor and taken away.

The owner, in tears as she related the story to us, concluded by stating that she was certain Heidi would have killed the other dog if she had been able to reach it.

A sad story and a difficult situation, to be sure, but not unlike many other cases we saw on the behavior service.  Most aggression issues in dogs can be traced back to some combination of poor socialization, negative early experiences and/or a genetic predisposition to fearfulness, but Heidi’s case stands out for me because of something unusual in her history – her aggressive behavior had been triggered very abruptly, in response to a single traumatic incident at precisely the wrong time in her life.

According to her owner, Heidi had been friendly and playful since eight weeks of age with none of the early warning signs we so often see in fearful puppies.  Both parents had outstanding temperaments, and were friendly with both people and dogs.  She went for daily walks with her owner and regularly encountered strangers and other dogs with no problems.  So far, so good.

So what went wrong?

Heidi’s front yard had an underground electric fence paired with a shock collar, commonly known as an Invisible Fence type system.  She also had a particular dog friend that she enjoyed playing with, a young Labrador mix who belonged to a neighbor.  The dog often came into Heidi’s yard to play with her, and the two could be seen wrestling and chasing each other all around the house almost every day.

One afternoon when Heidi was around seven months old, something happened.

She and her doggy friend were playing and wrestling as usual when they inadvertently strayed too close to the boundary line.  Heidi received a shock from her collar, yelped in pain and confusion, and redirected aggressively towards the other dog – who, for his part, reacted defensively and fought back.  A full-blown dog fight erupted in the blink of an eye, and the dogs had to be physically separated to calm down.

Under most circumstances, this type of incident would be scary and unpleasant but quickly shaken off.  But for Heidi, it was life-changing.

From that point on, it was like a switch had flipped inside her head.  She lunged and snarled at the neighbor dog whenever he came near the yard, and never played with him again.  Over the next several weeks, she began reacting aggressively toward other dogs on walks, at the vet’s office, and outside the window at home.  Her owner was at a loss to understand why her previously gentle, friendly dog was suddenly behaving like Cujo.

The answer lies in a perfect storm of variables, coming together in the worst possible way.

I have discussed the socialization period for puppies in a previous post – this is a developmental phase in which puppies are learning about the world.  Things that they see and experience in a positive way during this period will be seen as normal later on.

But – and this is a big BUT – the flip side is also true.  Young dogs go through two separate “fear periods” as they grow, which are essentially times when the pup is extremely sensitive to bad experiences.

The first occurs fairly predictably at around 8-10 weeks of age.  The puppy is very young at this point and owners are (hopefully!) managing her environment carefully and exposing her to lots of great stuff for socialization purposes, so often times this first fear period passes without any obvious signs or behavior changes – many owners never notice that it has taken place.

The second is more variable, but for most dogs it occurs as a 2-3 week period in late adolescence, somewhere between 6 and 14 months of age.  This one is sneaky – it pops up when owners least expect it, long after their tiny pup has become an independent teenager.  By this point, most of us are giving our dogs more freedom and no longer micromanaging how they interact with the world.  It can be a shock, then, when something happens at this age that turns all of our assumptions upside down.

So what happens during the fear period, exactly?

You may notice that your previously friendly, confident adolescent dog becomes spooky about certain things that don’t normally bother her… perhaps she refuses to go near a new garden flag in the yard, or barks at a man with a beard who says hello to her on the street.  This sudden increase in suspicion and reactivity towards things in the environment is normal – as long as you are cheerful and don’t make a big deal of the problem, it will pass on its own and you’ll have your familiar, happy-go-lucky companion back in 2-3 weeks.

The dangerous part is this: during this particular developmental stage, your dog’s brain is on a hair trigger, exquisitely sensitive to anything “bad” that may happen.  A single frightening or painful experience during the fear period can have a lasting impact for the rest of your dog’s life.

This is a phenomenon called single event learning – meaning that it only takes one experience to result in an intense, permanent emotional reaction to the trigger that caused it.  It makes a lot of survival sense in the wild, when a young wolf needs to steer clear of a dangerous predator without requiring multiple near-death experiences to teach the lesson.  But in our pet dogs, this peculiar little “glitch” in the brain’s memory processing system can have devastating consequences.

An all-too-common example:

When my oldest boy Remy was a puppy, he had his first nail trim after coming home with me at the age of 9 weeks.  (Recall that the first fear period normally occurs from 8-10 weeks of age!)  Unfortunately, one of the nails was cut too short – he yelped and struggled, and it bled briefly.  Styptic powder was applied to stop the bleeding, the rest of the nails were trimmed without incident, and he seemed perfectly happy five minutes later.

No big deal, right?  For a well-adjusted adult dog, probably not.

However… over the next few months, nail trims with Remy became progressively more difficult.  I was careful to make sure that he wasn’t “quicked” again, and he got plenty of treats and praise during the procedure every time thereafter – but it didn’t seem to matter.  My otherwise laid-back, cooperative dog would struggle with something akin to panic as soon as the trimmers appeared.

Why?  Because his single, isolated bad experience at 9 weeks old still held more weight than all the others put together.  Single event learning is powerful stuff.

And thus, we have Heidi.  Sweet, easy-going and perfectly dog-friendly… until the day she wasn’t.

Her owner left OSU that day much encouraged, with a training plan for Heidi and a better understanding of the things that made her that way.  And Remy, as an adult, learned to stand comfortably for nail trims again after many months of careful work to overcome his fear.  Thankfully, these kinds of behavior setbacks are not insurmountable – with time and effort, adult dogs can be taught better coping skills and form new, more positive associations with things that frighten them.

So what can we do with this knowledge?

Unfortunately, we can’t keep our dogs in a bubble.  The world is an unpredictable place, despite our best efforts… we cannot always control everything that happens to them or how they may react.  But, we can try to ensure that scary experiences are few and far between during these sensitive periods of development.

And if bad things do happen – we can recognize them for what they are, and be proactive in responding and addressing the fear before things get worse.

128 thoughts on “The Dark Side of Socialization: Fear Periods and Single Event Learning

  1. Wonderful post! I know you tackled more serious issues, but how much can we as dog owners do to help our dogs overcome the fear of getting their nails trimmed? I know walking them is supposed to help, but I have a few dogs whose nails grow like crazy. I rescued my dogs as adults, and they go to my vet/groomer for nail trims. I know what a struggle it is for them and the vet staff to trim their nails.At this point, is it a necessary evil for adult dogs to just get their nails trimmed as quickly as possible?

    1. That’s a great question! Nail trims are a huge issue for many dogs, and there are actually lots of things owners can do to help their dogs overcome their fear about them. I’m planning to cover nail trimming as separate topic sometime in the next few weeks, so stay tuned! 🙂

      1. I can’t wait. This is a very large issue for our rescue Shepherd who never got a fair shake at being a dog till we adopted him at 20 months old

    2. I had my dog’s nails trimmed by a vet until I went to a new vet and they took him out of the room. After a long time, I went in the back and saw them wrestling and pinning him down with a muzzle on. They could have killed him from overheating, and it was pointless, a command from me and he would have laid down for the trim. I had RIPE words for the vet and his staff and never went back.

      And I promised my dog that day I wouldn’t let him have a nail clip by a stranger again. So I learned how to do them, and five years and a new dog later plus I still clip my dog’s nails myself.

      You can have them dremelled (many dogs prefer this to clipping, but both take training.) I suggest educating yourself to do it at home as it will be a less traumatic experience than going to the vet in general.

      It’s worth considering if you have a tough dog, it’s better to do the training and reinforcement yourself in a condition of trust rather than depend on a veterniary staff (which does not always have training skills or time to deal with a fear-aggressive dog.)

  2. Thank you for this insight. As McCartney matures, I will be ever diligent to mind any untoward experience. As you say, no bubble, but being aware is key. Thank you. Love this blog.

    1. I’m glad you enjoyed it! It is definitely a tough balancing act… no bubble, but also not throwing caution to the wind. Fortunately, McCartney seems to be doing great so far! 😉

  3. I have a rough coat collie who used to take walks with me as a pup around the neighborhood until one day when assuming a noise that I did not notice.. scared him to death. I have never been able to figure out what it was. He ran up on the neighbors deiveway tail between his legs shaking like a leaf and i literally had to carry my 40 lb 6 month old puppy home. To this day.. 2 years..he hates walks. With the help of a trainer i can get him to walk 3/4 around the block with my husband and the two dachshunds i have until he is pulling badly and ready to run home. I would love for him to be as excited about walks as my wiener dogs are but i think it will take lots of time.

    1. Poor guy! Sometimes it can be very hard to tell exactly what the trigger was, in situations like this – dogs perceive so many things that we don’t. I’m glad to hear that he’s slowly beginning to warm up to the idea of walks again. It takes lots of time and patience, for sure!

  4. Well written in good understanding. I have two Borzois and both had this bad experienc during this period. My girl was biten in the back in the ring of a dog show, she was best borzoi….. She is five know and still have a problem when a dog walks behind her. And when he comes to near she now showes clearly that she dies not like it. But in other periods she snarled extrymle and I had to take her on short lash. My boy, now seven years, was attacked by a free running small dog whos owner did not look, he was occupied with other things on the parking. So I let me borzoy boy out from lash and then the small one runned away to its owner. This man has seen only his dog crying running to him and my dog trying to keep the other away from me. So the owner treated my dog with the foot with the hard shoes you use for skying. My dog cryed coming to my and the other owner behind and wanted to attack me. So I am not afraid of mens like this and I stopped him immediatly and calmed my dog taking him beside me. I told what happened. Than the wife of the owner came and said to me that she understands the situation and it was their faut not to have looked to their dog. I have two wonderful gentle soft big dogs, but it was hard work. They are now absolutely clean with other dogs, will say now they get bitten in den legs and foots when other dogs will attack as. They are gentle towards even smalest children and small gentle dogs. They love friendly people. They got my therapie dogs and we three are very closed and have a good time together.

    1. Thanks so much for commenting! It sounds like your dogs definitely had some bad experiences that left an impact – it can be very frustrating when other owners fail to control their dogs, leading to your dog becoming hurt or frightened. I’m glad to hear that they’re doing so much better now.

  5. Good article, it certainly re enforces my understanding of my dogs behavior towards other dogs. He was attacked as an 8 week old by my adult dog. They live together peacefully now but he’s still very cautious with his interactions with his housemates. He’s also extremely suspicious of other dogs.

    1. I can imagine! That’s always such a bummer, to have your puppy attacked at such a sensitive age – sometimes we can’t predict it or prevent it, but it definitely influences behavior for a long time to come.

  6. Very good article. I’m dealing with this with my 4 year old female german shepherd. She is great in class but when we walk our local riverfront she barks and lunges at anybody who acts like they are going to approach us…she will even bark if I speak to somebody on that path. We’ve been walking it since she was a puppy and unfortunately I believe we had a single incident happening that I was not aware of and it is going to be something I always will have to deal with now. I do believe it had to have happened on a walk. We are surrounded by people and dogs in our obedience classes and nothing….but when we walk — a whole different side of her comes out.

    1. That’s so interesting, isn’t it? I do think that oftentimes, we don’t even realize that something has happened – it’s fascinating that something so minor (to us) that we don’t even notice it, can have such a lasting impact.

      1. I had the same exact issue with my German Shepherd/Hound Mix. Similar to the article, but i can’t pin point what exactly triggered her behavior. It got worse and worse. I went to the behaviorist and he said that the dog is dominating you when the dog tries to lunge at other people or dogs. He then said that you are the bubble that she is protecting and will do whatever it takes to protect that bubble. He then explained to me and my wife that as dog owners, we need to stop treating them like kids and treat them like pack animals. If you don’t then the dog will assume the role of the pack leader and protect you at all cost.

        He then showed us what he meant by demonstrations that triggered what he was saying to us then proceeded with steps on how to train the dog to not lunge at people. It was very interesting!

        1. Poor pup! I’m sorry to hear that your dog had this problem as well – lunging at people and dogs on leash is, unfortunately, a fairly common problem.

          I’m glad to hear that things are going better for you now! I’m not one to argue with success, and I’m not sure what techniques the trainer you worked with may have recommended, but I would caution you to be wary of any methods that are based on dominance theory – this paradigm has been pretty widely discredited in the dog training world since the early 2000s, and can unfortunately do a lot of harm in some cases. Check out the American Veterinary Society of Animal Behavior (AVSAB) position statement on this topic if you want to read more 🙂

          Regardless, kudos to you for working with your dog to try and help her. I know this can be a very frustrating problem to deal with! Thanks so much for your comment, and I’m glad you enjoyed the article.

  7. Thank you for this article. My pup and I relate to it very much. I had a very well socialized, get along with anybody dog until she was chased and attacked by 5 off leash Jack Russels at about 14 mo of age. She was not physically harmed but it certainly rattled her and now at 8 years of age we are still living with the consequences. She is a 60lb powerful dog and decided she was not going to be attacked ever again and is inappropriately defensive. We had several heartbreaking dog fight experiences in the early years before I figured out what was going on. I wish I could have recognized what had happened earlier and done more about it at the time. She now has her “circle of trust” dog friends who she plays beautifully with but any one else is potentially a trigger for her. Despite having worked exceptionally hard at protecting her from any experience that might result in a dog fight, and working at changing her behavior I am shocked and horrified when so much is out of my control. i.e. 1 year ago despite written and verbal warnings my petsitter allowed his girlfriend to bring her dog over to my house when I was gone and my dog attacked her dog resulting in an emergency vet visit. My heart dropped. How can this happen in my own house?! I often ask myself what more I can do when I feel I work tirelessly to protect my dog and educate myself and others? The truth is that 90%+ of dog owners are exceptionally ignorant to dog behavior despite having lived with these creatures their whole lives so thank you for doing your part to change that.

    1. Your poor pup! What an awful experience to have at 14 months – no wonder she’s leery of other dogs. And yes, well-intentioned people who don’t know any better can be incredibly frustrating to anyone with a reactive or fearful dog… there is a lot we can’t control, and sadly other owners’ carelessness can have far-reaching consequences. Kudos to you for your hard work with your girl – it’s definitely not an easy road, but it sounds like you’ve done a great job with her.

  8. Thank you for the info. My two fox terrier mixes are rescued Dogpound dogs, that I got at different times. Lilly,now about 9,I got 7yrs.ago , Lucy, l picked her up 3yrs ago,she’s about 4now,and still a hand full. If there is commotion, excitement or one of the other dog gets excited or if aggression starts between any of them she will fight. (My mom has two Maltese).this has been going on for it’s not if a fight is going to happen it’s when , I have resorted to constant control ,now even lily is on leash more often, because of one gets going that’s when time has to slow down a notch. Barking and crazy mode really need help, forget visitor Lucy will bite and keep barking her head off.lucy and I need help not what sure what to ask for . Love my family and my two dogs but can’t afford another vet.bill or box of gauze for me .

    1. That definitely sounds like a difficult situation for all of you! I find that inter-dog aggression between dogs in the same household is one of the toughest issues I deal with – sometimes, the dogs in question just aren’t very compatible no matter what we do.

      The first step is to separate the dogs during high-risk times to prevent fights from occurring as much as possible; for some dogs, unfortunately, this may mean that they are physically separated at all times. I have a few clients who have managed this type of situation for years, with two dogs in separate parts of the house who never interact at all – but it’s very difficult for most owners to do as a long-term plan.

      The preferred goal is to work with the dogs to help them learn to be calm around each other in these types of exciting situations – sometimes we may teach an alternate behavior that can be rewarded, like sending both dogs to separate crates or mats anytime the doorbell rings and rewarding them there. If possible, I would recommend trying to find a veterinary behaviorist or a good reward-based trainer in your area who has experience with this issue – hands-on guidance can be really helpful, especially in the early stages.

      1. Thank you for responding to my cry for help. Glad to say I may have been on the right track. I’ve reacently started having both Lucy and lily on a leash at first I just kept Lucy in total control and focused but lily seemed to make some situations difficult. I will keep focused calm and rewarding and keep them both on a leash for control until the rewards prove to be. At times it seems so fine that is when I need to remember accidents have come surprisingly.thanks again.

  9. My dog went through single event learning twice. When he was 10 weeks old, an white spitz hit him while running. He hates till these days nordic-like dogs.
    And the second time, when he was maybe 6 or 7 months, I unwittingly splashed him with water, just few drops went on his nose while I wanted to give him water from my hands. He is almost 10 years old, but I still cannot empty a PET bottle in front of him and give him water from my hand on walk…

    1. It’s amazing how they register those little details, isn’t it? Nordic-type dogs only, and water from your hand. Dogs are much more perceptive than we often give them credit for.

  10. These are awesome reads as I am getting my 8 week old male GS this week. So excited! It is so hard to know what to do and not to do some times. As we don’t know how our animals think and what spooks them. I am hoping for the best each time I will introduce him to people and other animals. As well as noises.

    1. Oh, that is exciting – congrats on your new pup!! It can definitely be tough, because we know that experiences at this age are so important but none of us are perfect… all we can do is our best! Just knowing what kinds of things to be careful of is half the battle, I think. I bet you’ll do a great job with your boy 🙂

  11. Great article. We have 3 dogs, all rescues. The youngest (17 months) loves humans but is impossible with other dogs. Walking him is lovely until… another dog comes into view – whether behind a fence or also being walked. We think he was picked on when at doggie daycare – something we did on several occasion when he was 7 or 8 months, for socialization with other dogs. Fear aggression. He is a Saint Dane and outweighs me by 30 lbs. so you can imagine how difficult it is for me to walk him. My husband has to do it because I’ve lost all confidence in my ability to control him. Our old Great Dane and our Lab are joys to walk. Any thoughts on how to go forward?

    1. Leash reactivity towards other dogs can be a frustrating problem, for sure – especially with such a large dog!

      The good news is, this is usually a very straightforward issue to treat if you have a good reward-based trainer in your area or someone else who can help you. Normally, our main goal with these dogs is to create a positive association with seeing other dogs on walks – I normally use a clicker and high-value food rewards for this, but there are other possibilities if you’re creative. The tricky part is that for this to work, you need to keep the dog “under threshold”, or below the level of difficulty where he reacts by barking, lunging, etc.

      For this reason, I prefer to work with these dogs in a controlled environment the first several times, using a helper with a decoy dog at a distance. This lets us tailor the level of difficulty that we need to make sure that the dog can be successful, and also make sure the owner is comfortable with what to do before taking it on the road in real-life settings. If you can find a trainer in your area who has experience with this issue, I would definitely recommend getting in touch with them to see if they could give you some hands-on guidance.

  12. I think this is what probably happened to one of our malamute show dogs who decided that applause was unacceptable. It continued to escalate despite our attempts at desensitization until we decided it was not worth the effort and her stress. She is very happy in any other social context.

    1. Wow, applause… that’s very interesting. Sometimes they do key in on seemingly random, insignificant things and decide that they’re scary based on association with something else that happened at the same time. That’s definitely a bummer for a show dog – it’s tough to show successfully when you’re terrified of people clapping!

  13. Nice explanation! I rescued a dog from 7 months and he spent the first months of his life in kennels so he had some pretty big issues to get over when he came to me. He started with pretty big guarding behaviours, then he started attacking dogs, finally he started attacking humans. I spent a huge amount of time and money researching, hiring trainers and troubleshooting how to build back his confidence. All of his issues were based from fear. Now he is 3 years old and I have to keep reminding myself of how far he’s come. He’s such a happy boy and he even has a younger sister, now! We can walk through crowds with large trucks going past and he just happily plods next to me watching all the people around him because he knows he can defer to me when he’s not sure. He’s my life. Even though he has come such a long way I still need to be diligent because my responsibility is to protect him so I am careful to make sure he is not exposed to unpredictable dogs that have no manners.

    1. That’s such a great success story! It can be so hard to make up for those missed experiences in a kennel-raised puppy, but it sounds like you’ve done a great job with him. Sometimes that’s the most satisfying accomplishment of all – to be able to walk your dog down the street and have him happy and enjoying life, rather than being frightened of everything he encounters 🙂

  14. Wow, great morning read. I thank you. Like a lot of people who have left a message, I am the proud owner of a rescue girl called Loulou. She was dumped with her litter mates at just 4 weeks old (ish). They were found in a cat carrier. 6 starving pups. They were taken to a rescue centre and nursed back to health. We got Loulou at 5 months old. Day 1 was great, she sat on the garden wall taking it all in, she chilled on the sofa that evening, all seemed good. The next day her fear of the world came out. From the TVs being on, to grass moving, birds flying, sneezing. And her biggest fear people. We found a great pos trainer, who took each problem and set a plan. 2 years later, Loulou is almost a happy dog, she passed her bronze good dog award, and is super at agility. The only fear she has now is people. Anyone who comes into the house she barks like crazy at, even people who live here. (Apart from myself and my mum). If I have her out at training she won’t bark at people, just backs away, if I’m playing ball in the garden and someone comes in, she is okay, just if she is in doors when they come in. This is her only problem left, and I am trying my hardest to fix it. So reading this article has given me hope again. Thank you.

    1. Wow! Kudos to you and Loulou for all your hard work – it sounds like it’s been a long road. It’s so incredibly rewarding to see such a fearful pup blossom, slowly but surely, into a dog that can not only cope with life but even relax and have fun when she feels safe. The barking at visitors is definitely something that I think you could continue to improve on, if you want to – but it sounds like she’s made amazing progress regardless. She’s a lucky girl to have found you!

  15. So good to know Im not alone! My rescue girl who is now 1 is on anti anxiety medication as she is anxious aggressive. I can now (with meds and hours and HOURS of training) go for a walk with her around the block but she is terrified of me holding anything, men in hats and real estate boards. She is overtly social with some dogs and aggressive with others so she is always on a lead. Worryingly it is children and their unpredictability that she growls and barks at. She can nip too 🙁 I’ll never be able to trust her. It is a loss of a ‘family’ dog for me. The rescue say she was not like this when they fostered her. But somewhere something MUST have happened?! Thank you for your article. It is neither mine or the rescues fault. She just is who she is. Ill never give up on het but do worrry about her around children. Any more solutions or links to help much appreciated. Thank you. G

    1. It sounds like your girl has improved a lot since she came to live with you – kudos on your progress with her so far, I know it’s not easy! For many rescue dogs, their past is a bit of a mystery… we often don’t have much history to go on, so we don’t really know if their issues are related to lack of socialization, bad experiences, or even just being genetically predisposed to fearfulness. The good news is, we work with them the same way regardless – making sure they feel safe while slowly teaching more positive associations with the things that scare them.

      For your girl, the general approach I would take would be the following:

      1) Avoid situations that are scary for her as much as possible, unless you are using the situation as a training session and actively working with her. This is especially important since children are a trigger for her and she has nipped in the past – safety is the first priority, no matter what.

      2) Choose one trigger at a time to work on (strangers on the street, etc.) and teach her to associate good things with seeing the trigger. So for example, if you were working on reactivity towards people on the street, you could sit on your front porch and click and treat (if she’s clicker trained, praise is okay if she’s not) every time she sees a person. Over time, she learns that seeing a stranger = yummy treats, so she looks forward to seeing them rather than being afraid.

      If you can find a good reward-based trainer in your area who has experience with this issue, they could help you tremendously by giving some hands-on guidance in the beginning to make sure you’re comfortable.

    2. First, can I say I appreciate your concern about children. With a reactive dog it can be so easy for a devastating bite to occur. Can I suggest muzzle training as a way for you to be able to enjoy walks with your beloved dog without fear of an accident? I’ve used it myself and after really working to make the muzzle fun for my dog (you really start slowly with this in a happy safe place) he now views the muzzle as a tool just like a leash and we are both able to enjoy our walks without fear that an accident will happen. My dog can pant, drink and even get treats through his basket muzzle and it helps us both enjoy a “normal” doggy life in public. Maybe this is a tool that could help you. Just a thought…

      1. Amanda, thanks for this suggestion! I agree that basket muzzles can be a great “safety net” for reactive or aggressive dogs.

        I do caution owners to be sure that they are not using the muzzle as a substitute for appropriate management or training – our goal should still be to make sure that the dog is comfortable and not over-faced by the situation we are putting her in. But as a way to have some piece of mind that nothing catastrophic will happen in the event of a problem, they can be fantastic tools! 🙂

        1. I totally agree! I actually worked on BAT training with my dog in public with the muzzle on because no matter how you try to control distance with strangers in training, you can never predict what will happen once you are ready to take your dog into a public space. Kids especially are vulnerable and unpredictable. So, I totally agree it’s not a license to press the dog’s boundaries, but if you are dealing with a dog who has bitten people you really should never train in public without a muzzle. It’s just not safe or fair to the public. A bonus I found in using the muzzle is people tend not to run up to a muzzled dog like they do otherwise and this actually helps a reactive dog by giving them that space they need from strangers and the other bonus is if the owner is calmer because she knows no bite can occur she will most definitely pass that calm emotion down the leash to her dog.

          1. That’s perfect, yes – I agree with every word of this, thank you! That is the perfect way to use a basket muzzle in training. As a safety net to avoid problems if something unexpected happens, and also as a deterrent to keep John Q. Public from wandering over and trying to pet your dog 😉

  16. I am dealing with an issue with my GSP boy. He was always a very confident boy.. happy, loved everyone. He has been very well socialized..has been shown, hunts, competes in NAVHDA, has done Obedience classes since he was 12 weeks old, got his CGC… until he was @ 13 months old.. it was like someone flipped a switch.. he went from loving, confident Mr Social to spooky, fearful of people except myself and my husband… we have continued to socialize and make things fun for him as well as positive..he is better but not there yet.. any ideas, helpful hints, suggestions?? He comes from very confident, social lines and he just turned 2 years old.

    1. Poor guy! That’s such a frustrating problem, when something happens to change everything but you don’t know what it was. It sounds like you’re on the right track with your boy – I would definitely continue to get him out and about in different places, making sure to use lots of rewards and keep things at a level that he can handle. If he’s really reactive and anxious, it may be worth talking to your vet (or consulting a veterinary behaviorist, if needed) about pros and cons of anti-anxiety medication. Some dogs like this do very well with an SSRI like Prozac, which can then be weaned off in 6-12 months if things are going well.

      If he’s reactive to certain things in particular (like people or other dogs), then you can also work on those specific triggers – stand at a distance and click and treat (if he’s clicker trained, verbal praise is okay if not) every time he sees a person (or dog, if that’s what you’re working on). Over time, he learns to associate seeing people with great things, and also learns to automatically look at you for his cookie rather than barking or shying away 🙂

  17. I do not believe in “fear periods”. I believe the early issues are related to how humans handle the homing of young puppies. To stick a puppy in a car or crate, for the first time, and take them totally away from their family on their first day away from the litter ever is a cruel practice. I would also be scared as would you. Responsible breeders have early car experiences, separation and returns, visits to the new home with returns, and separation in sleep prior to homing. Also to be out and about between the ages of five to 12 weeks so that loud sounds, trucks, beeping horns, unfamiliar dogs and people have all already been encountered. The biosensor exercises from Day 3 to Day 15 also make a huge difference bounce back from stress. Stress must be introduced to a litter early so they learn that a stressor is not the end of the world and changes behavior with first event situations. Breeders must take more responsibility. Of course, that begs responsible breeders, but also shelter workers and rescues need to have more awareness of what can be done with fear, stress and recovery early in life. And how to handle that with a fearful dam who may be in a rescue situation for the first time and imparting that fear to a litter. Jane Killian is doing some excellent videos and books on the topic. is a great first stop for anyone wanting to work with young dogs to prevent these issues.

    1. I definitely agree that breeders can have a huge impact on their puppies’ resilience later in life – those first weeks of development are so critical, and they’re already past by the time the new owner first brings the pup home. And thank you for posting the link to Jane Killion’s website – she does have some fantastic information for breeders and new puppy owners!

    2. Puppy Culture is a great resource! But just to be clear Jane Killion does acknowledge fear periods in her Puppy Culture DVDs. All the suggestions you make about breeders building an ability to bounce back from stress is so true and important, but Jane does acknowledge the fear periods exist and cautions breeders to work carefully with puppies during these periods.

  18. I’m a dog breeder and had a 10 month old boy returned to me 3 months ago. I don’t know the backstory or details about what happened that led up to his return. I was only told by the owner(s) that his “aggression had amped up over the past week and that there was nothing more that could be done for him.”

    Upon his return, he was not in good condition. (severe cherry eye, upper respiratory infection, flea infested, and underweight).

    He had developed a severe cherry eye some time during the fast growth period for a giant breed dog that had been left untreated. The cherry eye was so severe that it covered the entire eyeball on both eyes. Basically, this boy couldn’t see.

    On top of this, he appeared to be unsocialized to people from what I could see. He was terrified of new people and strangers and he was over-the-top terrified at the vet.

    In the beginning, I used a muzzle to walk him in order to avoid an accidental bite. He was very gun shy of having me or anyone else put the hand over his neck or head (to put on a collar and leash). He would cower, make himself small, and pee on himself whenever I tried to put my hand over his neck and/or head.

    The first time I tried bringing him to the vet for corrective eye surgery (muzzled for everyone’s protection), he was so amped up and scared, that the pre-anesthetic injection didn’t work. His adrenaline overtook the injection and he didn’t go to sleep.

    The second time I brought him to the vet for the corrective eye surgery (muzzled again), I gave him 3 Valium tablets 2 hours before. When I got him into the vet, he was terrified again. The vet assistant had to use a catch pole to hold him in place because none of us could hold him on the leash with a prong collar. Then the vet assistant had to put a towel over his face, so he couldn’t see when the vet gave him the pre-anesthetic injection. Finally, the eye surgery was done.

    Afterwards post-surgery, when I brought him home, the first thing he did was stare up at the sky for about 10 minutes. It’s been three months since this boy has been with me, he is a work in progress. His confidence is building from regaining his eyesight, and from continual exposure to new things, walking down to the vet and giving him a cookie when we go inside, then leaving; visiting the children’s park to “watch” the children, going on walks downtown and allowing him to approach on his terms new people, then giving him a cookie as a reward for having the courage to approach a stranger.

    I have high hopes for this boy. He’s not a bad boy. He’s not aggressive in my eyes. But he is definitely fearful. I don’t know what happened to this lovely boy at the first owner’s home. I will never know.

    If I cannot find this boy the right home, he will stay here with me.

    1. Oh, poor pup – every breeder’s worst nightmare, I’m sure! Whether it was incredibly poor socialization or outright mistreatment, it sounds like he’s had a long road to recovery so far. He’s very lucky to have you as his safety net!

  19. This is what happened with my Lucky. I rescued him (abandoned at my church) at 8 wks. I have 3 older female dogs who were wonderful with him, showing him the ropes. I socialized him thoroughly with other dogs, people etc. Happy go Lucky, friendly to all nice pup. Took him to puppy class, all went well. Took him to intermediate class, all was well UNTIL the last 2 wks of class, a new dog entered the class and her FIRST meeting with Lucky she lunged at him, growling, teeth bared . No fight, no blood. But this ONE experience (at approximately 1 yr old) has been almost impossible to overcome. Lucky would not go anywhere near this other dog. Wouldnt even go to the class. (I dont believe in forcing animals if they are clearly afraid). I have been able to take him around other dogs for BRIEF interchange of greetings but any dog that remotely resembles the ‘evil dog’ (large, brown) he will not approach. And he will not continue to learn in a class setting. He is on high alert the entire time ‘just in case’ the evil dog appears. It’s been 6 months now. I can finally take him to Pet Smart (where the incident occurred) though not to the side of the store the training area is located.

    1. Poor Lucky – that’s so frustrating, isn’t it? You can do a great job with early socialization and everything can be going great, and them BAM… something totally out of your control throws a big wrench into things. It sounds like you’re doing a great job of gradually getting him re-acclimated to other dogs and public places – you’re exactly right not to force him, it’s always better to let him go at his own pace. As time goes on and he has more and more good experiences, his anxiety should continue to improve – lots of time, patience, and rewards for being brave!

  20. This is a well written article, with excellent incites. I do wish there had been more discussion on the use of invisible fences and shock collars. It sounds like this was a trigger far more than the incident with the other dog, the other dog appeared to be responsible for Heidi’s pain in her mind. If Heidi had been shocked multiple times before this incident as other dogs walked near her yard, it likely may have been multiple learning incidents that resulted in the fear development.

    1. Ah, invisible fences and shock collars… I am not a fan of them for many reasons, but figured that opening that particular can of worms might derail the post a bit 😉 But yes, I agree with you – she could very easily have been shocked on more than that one occasion in association with dogs walking past the yard, which could certainly have been a contributing factor to her problem.

  21. Had a similar incident with a show dog. Attacked by gSD at 11 weeks… attacked by another 2 gsds and a husky at 23 months and then AGAIN lunged at by a 5 month old gsd at show handling class. The pup dragged her owner up behind me to go for my bitch (a whippet). Apparently she has a bull’s-eye painted on her back end! She is a lovely female and has been absolutely ruined now and suffers severe anxiety especially if I take her out and we go to a show or any event where there are other breed dogs. If it’s big and it’s black she freaks out and Barks her head off. I have her add a new handling class wear person running it knows what she’s doing and we are starting to be able to at least get her on the table and allow another person to put their hands on her. Yes it even affected how she stands for examination on the table. My worry is that because she has this high anxiety level now that I should not breed her because research has shown In humans that that kind of anxiety is passed on as epigenetic damage to offspring and they are born anxious and that this anxiety passes down for several generations. 🙁

    1. How awful for your girl! It does seem like some dogs have a “kick me” sign on their back, for whatever reason. A few experiences like that can completely derail a show or sport dog’s career, so I definitely sympathize.

      As far as breeding goes, it’s definitely an interesting question. We’ve known for quite a while that stress in the dam during pregnancy can have an effect on the pups’ anxiety levels and general resiliency due to the high levels of stress hormones the babies are exposed to in utero, but the research on epigenetics is adding a whole new layer to consider. As if breeding decisions weren’t complicated enough as-is!

  22. This post is very timely as I’m dealing with dog-reactive aggression in my Portuguese Water Dog. She was socialized on a daily basis – walking neighborhood, visiting Lowe’s & Tractor Supply, play time with other dogs, etc. She was very friendly up to her first estrus (1 yr old) & then became aggressive toward little fluffy dogs. I was told it could be a false pregnancy because she was fine around other PWDs. It steadily worsened so we went through a 7-wk Behavior Solutions class a year ago & have practiced everything learned there. It took a year, but she no longer goes berserk when seeing dogs walking while driving with her in a crate. She still gets huffy with adrenaline, but stays calm & gets a treat for it. She is on leash or 50′ line in back when we’re outside (no fences allowed), including when I remove her from the crate in the car if my garage door is open. She is very smart & sharp eyed while “on duty” ALL the time believing her “job” is to guard me, my home + ALL 40 townhouse in this small quiet subdivision. However, in just the last 2 months, she was aggressive to 2 women who were visiting, but had doggy smells – while under control on leash. I am taking her to be evaluated tomorrow morning by a trainer with 30+ years of experience in reactive aggression & eCollar use. I am very interested in what you think of eCollar training!

    1. Poor girl! I really like PWDs – we see several of them as patients at our vet clinic, and they’re very popular on the agility circuit in my area as well. Very neat dogs! It sounds like you’ve come a long way with her so far, so kudos for that 🙂

      Regarding e-collar training… to be honest, I am not a big fan of this technique for dogs with any type of reactivity or aggression issue. Unfortunately, studies have shown (and my experience bears this out, as well) that the use of any kind of punishment for this behavior, whether leash corrections with a choke or prong collar, or an electronic collar, carries a significant risk of worsening the aggression over time.

      When I work with reactive or aggressive dogs, our main goal is to teach the dog over time to associate great things with seeing other dogs, or people, or whatever their particular triggers are. This often overlaps with rewarding calm behavior, which is an added bonus. If this is our goal, then it’s somewhat counter-productive to add corrections into the mix – many dogs end up associating the correction with the sight of the trigger, which can really inflame the situation.

      But of course, your trainer’s experience with the issue may be very different – just my two cents, for whatever it’s worth! I know this can be a very frustrating problem to deal with, and it sounds like you’ve done a great job with your girl so far.

      1. Thank you for this response

        In my experience when you have a dog that is reactive and already has problems with fear, guarding, possessiveness ect. the e-collars are not only detrimental but many times have actually caused a problem to intensify to the point that the dogs trust nothing and no one!

        Many owners and handlers think this will be an easy solution to the problem when in all reality they cause many dogs to be abandoned or turned into shelters or worse!

        It takes a very dedicated owner to spend the time to fix these problems properly.

        And the most common problem is in your statement that
        ” If this is our goal, then it’s somewhat counter-productive to add corrections into the mix – many dogs end up associating the correction with the sight of the trigger, which can really inflame the situation.”

        I have seen this so many times and it never fails to mystify me that the owners or handlers do not realize this as everything about their pups reaction is signifying that this is happening.

        I am going to meet with a 2 year old pup that has all these problems and more and I know that the hardest part will be convincing the owner to put her whole heart and soul into a positive solution and that there is no overnight success the solution will take patience, persistence, consistency and a whole lot of time and effort but in the long run it will be worthwhile.

        Everyone that deals with these concerns just need to understand that their is no 2 second solution but saving these pups is so worth the time and effort to help them lead a normal happy life.

        And in return they will give so much back and success is rewarding in itself!

        1. Yes – sadly, I have also seen a few very sad cases of aggression that had been dramatically worsened by the use of a shock collar. For this reason (as well as the scientific literature on the subject), I try to dissuade owners from using these types of techniques. Not every case has such dramatic fallout, of course, but when it happens it’s quite tragic for everyone involved. And I’m rather skeptical of what the dog has actually learned, in cases where it appears to work – in my experience, many of these dogs are behaviorally “shut down” rather than truly calm and comfortable around their triggers.

  23. I have this aggression/reactive-to-other-dogs problem with my Bel Malinois, Swagger, he is 15 months old and a really happy dog. EXCEPT when other dogs, usually larger dogs, are approaching or nearby. We can’t go to normal group training, because there are …other dogs. I struggle with how to desensitize him using trusted, well-behaved dogs when I don’t have ready access to any. I’ve spent months and hundreds of dollars on classes, where he does behave once in the secluded room with the five familiar dogs, but any “new” dog is still a problem. I’ve done a couple of Dog Shows, and somehow my strict handler-friend (male) can keep my dog from acting out, while I can’t (I’m female). He goes berserk and bares his big teeth and I am stuck pulling on him to get away. When he’s nervous, he will not take ANY type of food/treat. The ONE THING I’ve found that he will accept as a distraction is playing tug. After two sessions of use of tug, he now will “see a dog, look at me, then look at tug, we play tug” and this keeps him under threshold. Can you suggest how to work with this new info and “graduate” him off needing the tug? I have to keep this dog busy training and doing things, because he is a high energy intense dog. But trusting other dogs/owners to behave so MY DOG will behave is a fool’s wish. I need to get him through this, while he’s in this stage so we can enjoy doggie things. Thanks in advance! Barb and Swagger

    1. So glad to know I’m not the only one who dreads seeing other dogs on walks, etc! I’m going to try the tug but nothing so far has worked… my 4 year old lab had this problem and through long and arduous training, we’re past the reactive point (though I keep my eyes open for any signs). She is only 85 lbs. – big boy, George, however is 160 lbs. and I certainly cannot stop him if he passes the tipping point. I need a dog whisperer!

      1. You’re definitely not alone! In fact, leash reactivity (towards other dogs and/or people) is probably the most common problem I deal with for private training – lots and lots of dogs have these issues, so don’t beat yourself up 😉 It sounds like you’ve made a lot of progress with your girl so far, so kudos for that – I know it’s not an easy road!

    2. Swagger sounds like a challenging boy! Good on you for figuring out that tug works well for him in these situations, even if food rewards don’t – sometimes we have to be creative 🙂

      I agree with you that one of the toughest parts of working with a dog-reactive dog is the difficulty of finding other dogs to practice with in a controlled setting. Have you ever tried attending a group class just to hang out on the periphery and practice his “look at dog, look at mom, tug!” skills? This works really well for outdoor classes since you can usually choose to be far away if you need to, but you may be able to make it work for an inside class as well if there is enough space. You could also try attending some shows just to walk around the outskirts practicing with him, then go home – no pressure to perform, no putting him in the ring. Then go back to showing once he’s comfortable hanging out in the venue with no problems.

      Most of the time, with reactive dogs, I find that distance is a huge factor in being able to work with them successfully – you need to be able to start far enough away that he can handle it with no problem, then gradually work your way closer. It’s much harder to make progress if you’re always right in the thick of things, because he’s always right on the edge of going over threshold even if he’s not overtly reacting.

      Not sure if you’re familiar with Denise Fenzi’s online classes, but they’re really good and there is one in particular that is focused on working with fearful or reactive competition dogs – it’s called Dealing With the Bogeyman, and will actually be offered in August if you’re interested in taking it. Here is a link to the class description – might be worth checking out!

  24. Great article! I knew about the fear imprint between 8-10 weeks but not the later one.
    I had a large make Great Pyrenees mix who hated nail trims. I always did them with my dogs sitting or laying down. Finally I tried letting him stand and worked him similar to my horses. What a tremendous change that was! From nightmare to easy peasy! I got him off the streets so will never know what his issue was. Just finding a position he was comfortable with made all the difference.

    1. It’s amazing, isn’t it, how much difference a slight change like that can make? I would definitely agree that figuring out how to make the dog comfortable is the first step towards working on anything they’re afraid of.

      Thanks for reading!

  25. I have an extremely dog aggressive female GSD also. I had her imported from Czech. I suspect she was attacked by another dog as a puppy. She is a smallish GSD, 50 pounds at nine months. She will, however, engage any other dog or dogs with no hesitation. She is working line bred, which increases her intensity. We are working on her focus to me when other dogs are around. We train for IPO, other dogs around us are leashed and in control. It’s getting better, but she will never be dog friendly, other than to our other dogs, her “pack.”

    1. It definitely helps when the dogs around you are under control and not running amok! And don’t beat yourself up if she isn’t “dog friendly” – as long as she can function and mind her own business in the presence of other dogs, that’s a perfectly reasonable goal.

  26. Thanks for the article. I have a 9 month old female German Shepherd who I believe, is going through a fear period right now with strangers, especially men. I worked hard early on with her socializing and much as I could. She was never this wary or unsure of strangers. I’m hoping this will pass. What I have been doing lately is increasing the distance between strangers that is comfortable for her and rewarding her when she focuses back to me. It seems to be working much better, but I believe we still have a way to go before she will be super comfortable. Would you consider this an appropriate approach to correcting this behavior, or would you recommend something else? Thanks in advance!

    1. I think that approach is perfect – when in doubt, just give her plenty of distance and reward 🙂 It sounds like you’re doing a great job with her so far. Be patient and stay positive – it will pass.

      1. Good to know we’re on the right track, and yes staying positive and patient will be the key, thanks for the reply.

  27. Very interesting article. My Miniature Schnauzer is very fearful…but I’m thinking it’s in her nature. We’ve had her since she was 8 weeks old. At 10 weeks, my father-in-law (6′ 5″) came for a visit. She wimpered and hid in a corner. Next we visited my folks. When relatives came to greet us – she screamed as if being attacke. Then with every trip to Petco – she’d scream at any/all dogs. They wouldn’t even take her in the puppy socialization class….because they thought it would be traumatic for her. Her mom seemed fearful…but not to this extent.

    We took her to doggy daycare (4 mo) for a few weeks. She screamed for several minutes her first visit. We had a personal trainer come to the house. Got a 2ND pupy when she was 6 months old to help her…whom she adores. She’s 1.5 now and barks aggressively and lunges at all other dogs. It has improved a tiny bit since puppy obedience class. She calms down more quickly now…unfortunately I had to pull her from class, because she was suffering from kidney failure. But now that she’s recovered, I’d like to address this issue some more.

    1. I’m sorry to hear about your pup – she sounds like a very anxious girl! It is definitely not normal for a 10-week-old puppy to be so overtly fearful of strangers. Most puppies this age are obnoxiously friendly and curious about everything – so I’m always worried when I see a pup that hides or screams when being handled.

      Based on your description, and the fact that the dam appeared anxious as well when you met her, I would hazard a guess that your pup inherited a genetic tendency toward fearfulness. Unfortunately, this is a very heritable trait in dogs – pups born to a fearful dam and/or sire have a high risk of being somewhat fearful themselves, sometimes in spite of good attempts at socialization.

      There is still a lot we can do to help dogs like this, although to some extent we do have to accept that this is who she is – much like a shy or introverted person. She may never be a social butterfly, but having her learn to be comfortable with normal, everyday occurrences in her life and enjoy activities like walks and playtime is a very reasonable goal.

      I would definitely recommend trying to find a veterinary behaviorist or a good reward-based trainer who has experience with this issue in your area – he/she can help you identify which specific triggers or situations you would like to work on first, and put together a training plan to start moving forward 🙂

  28. This piece has been so informative for me. My dog is petrified of banging sounds (gunfire, fireworks, thunder & lightning), he will bolt if we are outside when he hears these noises. Unfortunately the desensitisation CDs don’t seem to be working for him as I think he’s not fearful to this sound. Any advice would be greatly received!!

    1. This can definitely be a tough problem! Many dogs with noise phobias can benefit tremendously from medication to help with their anxiety, such as Clomicalm or Prozac – it may be worth discussing this with your vet if you haven’t already to see if he/she feels it would be appropriate for your boy.

      From a training standpoint, desensitization can be tricky because we may not have a good way of gradually increasing the intensity of the sound while we work on the problem – thunderstorm CDs are great in theory, but they don’t work for all dogs. What you can try doing, if he’s willing to take any kind of treats in these situations, is work on rewarding him immediately every time there is a loud noise.

      For example, during a thunderstorm, you could sit in your armchair with a bowl of hot dog slices. Every time you hear a clap of thunder, tell him “Good boy!” and toss him a bite of hot dog. The tastier the treat, the better this will work – so go for the big guns here. If he’s willing to eat the hot dogs, this will help over time. If he’s too anxious to eat anything, this is where medication may be helpful.

      1. Hi! Many thanks for the advice. I shall give hot dog sausages a go, Rufus loves any foods (he’s a dog!!) but he doesn’t get these usually so I’ll save them for these situations. He has a den that he goes in when he feels anxious which I think has decreased the amount of anxiety he feels.

    2. When my weim was young, while she was eating my husband would shoot a starter gun outside. A bit away from the house, but loud enough to startle. He did this as pre-hunting training so she associated the pop with something good. She does not hunt, but is now she’s not afraid of fireworks or thunder.

      1. Hi!, thanks for your advice. I think this is a great tip as, unlike the desensitization CDs, it will sound the same as the sounds he reacts adversely to & it will be outside the house. I shall try this. Rufus is a rescue dog & he was 2 years old (approx) when we adopted him. He was found in a region of Spain where they have alot of hunting & fireworks. He is a gun dog breed & it may be that he was rejected by a hunter. He has been with us for 18 months now & he is socializing with all the local dogs well and is friendly to humans, albeit nervous on first meeting. He really is the sweetest dog!!

  29. In general, I don’t think these electric perimeter fences are a good idea for other reasons as well. Too many times, even older dogs have a bad experience with them and never want to enjoy their yard again. Just not worth it to me. Awful to have a big, beautiful yard and some dogs can’t get over the very negative experience where the only thing happening was — outside in the big, beautiful yard.

    1. Generally speaking, I tend to agree with you – I’m not a huge fan of electric/underground fences for several reasons, including anxiety and barrier frustration issues which seem to be a problem for some dogs. I realize that some owners may not have many options due to HOA restrictions, etc. – so in this case I recommend that people carefully consider the pros and cons and make their decision accordingly, and be on the lookout for any sign of a developing problem.

  30. We had a similar issue with our Great Dane Mythos, we were extremely careful in bis socialization “had dog will travel”, he went everywhere with us and had great experiences everywhere he went. even at the dog park we were careful to make sure the play never got out of control. Then one day it happened he was about 9 months old , we were are the dog park and i saw a Guy come in with a Pit bull (I’m far from a pit bull heretic, but I digress. This young man came in on his cellphone completely carefree and paying no attention to his dog or others around. He has never been to the park before to my knowledge, i was later informed this has happened before and I watched as he unleashed his dog, and wandered away on his phone as his dog turned and charged directly at Mythos. I couldn’t get to either of them in time and the ensuing fight was quite vicious,I had to separate the dogs myself as the owner was no where to be found. We left immediately but the damage was done. From this point on Mythos seemed to have random aggressive reactions to dogs, some he would walk by without a care in the world, some he would lunge at, and for the longest time we didn’t know what it was that really triggered him. Some dogs he was aggressive to were small loud barkers, sometimes it would be a medium sized dog that was quite, but looked at him in a challenging way and 90% of Pitbulls would trigger him. he is 0% aggressive towards humans, the vets love him and is a spectacular Dane in all other respects. It’s taken allot of work , and were still not 100% but as he ages it seems to get better as time goes on. It only takes that one time.

    1. Sadly, yes – for many dogs, one unfortunate experience at the wrong time can have a lasting impact. And it’s interesting, isn’t it, what kinds of details they pick up on? I’m glad to hear that your boy is improving as time goes on.

  31. Thank you for this valuable info. Now I understand some things I didn’t have a clue about.

  32. Thank you so much for this blog! I’ve learned so much already. I have two seven year old Golden retrievers, and we are adding a new golden puppy to our family in a few weeks. I’d love to hear your thoughts about positive ways to introduce the new pup to her/his new dog brothers.

    1. Congrats on your new puppy! As far as introductions go, ideally I would do this in a neutral area like a park if possible – let the two adults say hello to the pup and sniff for a few minutes, then go on a walk together if you can. This lets the dogs get used to each other’s company while they have something else to focus on, and often helps to minimize issues such as the puppy pestering the older dogs to play. Once you get home, bring all the dogs in together. The novelty of meeting each other has often worn off after the walk, and they may be content to quietly ignore each other for the first evening – this is perfectly fine.

      In general, I would monitor closely for any signs that the puppy is harassing the older dogs and not taking their hints when they want to be left alone – if this happens, call the puppy away and redirect her to a toy or some other activity. As the pup gets older, she should get better and better at reading social signals from the adults so this generally gets easier with time.

  33. Thank you for this blog post. We had an aggressive Shiba Inu whom we acquired as an adolescent. But the botheration was that he was not predictably aggressive. And he could hold a grudge – waiting and lurking until he could get a hated person alone and bite them. And when he decided to attack he was silent. We homeschool our six kids and sometimes he’d have it in for one of their friends. It got to the point that I had to wrap his leash around my waist and sort of wear him whenever they were around. It was so extraordinarily stressful having to be on guard 24/7. He was medicated and put on a strict training program by a doggie behaviourist and it got a little better. We kept him alive (the breeder and vet both said put him down) and kept everyone safe for 11 years, but never really enjoyed him as a dog. At 11 he got cancer and suddenly turned into a nice dog and we were finally able to enjoy him for the last two years of his life. I don’t know what flipped his switch back to “nice dog” – he did not take any medications for his cancer. but my happiest memory was the day when, at 11.5 years old, he wagged his tail when I came in…for the first time ever.

    1. Your boy definitely sounds challenging! I’m glad he got to enjoy his last couple of years with less anxiety and reactivity, and you got to enjoy him as well. With aggression issues in dogs, unpredictability is one of the most difficult factors to deal with – so kudos to you for managing it so well, for such a long time.

  34. Can you provide links to research articles establishing these “fear Periods?” How has the existence of these been proved?

    1. Most of it dates back to Scott and Fuller’s “Genetics and the Social Behavior of the Dog” published in 1965, detailing the results of their 13-year study on learning, development, and social behavior on dogs. It’s quite lengthy (450+ pages), but full of interesting stuff if you have interest in behavior science.

      A bit more recently, Dr. Michael Fox has also done some good research on puppy learning and development that supports Scott and Fuller’s conclusions – his book “Integrative Development of Brain and Behaviour in the Dog” is another great read on this topic.

      Observations and experiences of many people with expertise in the field also back up these general conclusions – this is not the same as a rigorous double-blind study, to be sure, but worth noting nonetheless. So, based on their own experiences as well as scientific literature on the subject, the existence of fear periods in canine social development is an accepted truth by the vast majority of experts in our field 🙂

  35. Great information, thanks. Another thing that occurs to me is that in a wild dog/wolf pack, each pack would have a defined territory and a closed set of pack members, with only death or birth changing the membership. So in today’s world, we may walk our dog in the same places (territory) but they constantly meet unfamiliar dogs. This may be stressful and confusing to the canine brain? But, to argue with my own nascent theory, my dog Diva was best buddies with a pit bull at the local park. They couldn’t wait to see each other and played and roughhoused together a couple of times a week. One day, as we were all just standing around chatting, the pit bull attacked my dog, for no reason that was apparent to us humans. My dog stood her ground, but didn’t escalate and the owner pulled the other dog off. It was never the same with them, and I know my dog was shaken up. There is still so much we don’t know about doggy behavior!

    1. Definitely some interesting thoughts – thanks for commenting!

      In general, we do have to be cautious about drawing parallels between the social behavior of wolves and other wild canids vs. dogs, because we know that there are important genetic behavioral differences – for example, feral dogs live in much looser social groups than wolves with members coming and going frequently, and do not have a strictly defined social hierarchy. So it stands to reason that domestic dogs would be more open to meeting unfamiliar individuals than their wild cousins.

      But yes, I think that this general idea is probably one reason that socialization and fear periods have evolved the way that they have – they are a holdover from a social structure that made sense for their wild ancestors, with a closed social group and not much reason to be open to new things after reaching adulthood, even though these traits may no longer be adaptive in their current role as pets.

  36. Where abouts are you based? I have the exact issue with my 3year old boxer. Beautiful dog until she is around other dogs – all except one that she loves dearly. She used to be so well socialized up until she turned one where she started getting inappropriately defensive to dogs in parks and on our walks. It’s a nightmare. We have done training but I don’t know what else to do for her. It’s disheartening at times.

    1. I am in Huntington, WV. If you aren’t near me, you can search for a behavior-oriented veterinarian or a reward-based trainer in your area using these websites:,, and

      This is usually a very treatable problem, with a good training plan in place and someone to give you some hands-on guidance in how to work with her. I’m planning to do a post later this summer on training methods for working on reactivity and aggression towards other dogs, so hopefully that may help you also! 🙂

    1. Yes, indeed – the use of a basket muzzle and Gentle Leader when walking, along with a back-up martingale collar, was one of the recommendations that she left with 🙂

    1. Poor pup. Many dogs are very nervous about meeting other dogs on walks – understandably so, since you never know how the other dog may react to a meeting!

  37. Great Blog. Is single event learning isolated only to the two fear periods you mentioned? Can a dog over 18 months be exposed to a single aversive event which has lasting repercussions?

    1. We know that dogs are more predisposed to single-event learning during fear periods, but it can happen at any time. In my experience, younger dogs that are in these sensitive developmental stages are more prone to have very dramatic fear reactions to relatively minor events vs. adult dogs, but a bad experience can have long-lasting consequences at any age.

      1. Thank you. It’s good to be aware that the sensitive stage means the event may seem minor to us but have dramatic consequences for the young dog. Keep up the great blogs. I’m really enjoying them.

  38. This sounds like my rescue beagador! She is 11 months old and has suddenly developed separation anxiety! Do you have any advice for this? I can’t work from home right now so the weekends are the only time I can really work with her.

    1. Poor pup! Separation anxiety can be a tough problem to deal with – I’m hoping to do a post on this topic in the future, since it’s well worth discussing. With separation anxiety cases, I normally focus on trying to provide the dog with things to keep them occupied while you’re gone, such as chew items or puzzle toys – this helps to keep her busy when she’s by herself, and also teaches her over time that you leaving predicts yummy treats and fun things for her. You may want to try a Kong stuffed with peanut butter or spray cheese, or putting her breakfast in a puzzle toy like a Kibble Nibble or Tug-a-Jug for her to work on while you’re gone. A DAP pheromone collar or natural calming supplement like Composure may also be worth a try.

      There are published protocols for desensitization to being alone by using a graduated departure plan, but I find that this is very difficult to put into practice for most owners, and can make things worse if not done correctly. Because of this, I don’t use them very often – but if you’re interested in giving something like this a try, a good reward-based trainer or veterinary behaviorist can help you develop a plan that works for you.

      If your pup is too anxious to be interested in treats while you’re gone, then anti-anxiety medication may be really helpful for her – you can talk to your vet about this to see if he/she thinks that it would be appropriate for your girl.

  39. Do you have more details on what her owner did training wise?

    I have the same issue with my 2 year old shepherd. Except I cannot think of any happened that happened to her, to make her dog aggressive.
    I believe it suddenly changed around the 6-7 month mark. She was spayed then, but then people also say she could have just matured and that is how she is.
    She hasn’t gotten so bad with other dogs that I’m personally afraid to take her out in public. She goes crazy if we our outside on the front property of our house and another dog walks by. New dogs cannot come near our yard or inside, or else she will go in attack mode. Even with more training, she has not improved one bit.

    1. I’m sorry to hear about your girl’s issues – I know this can be a frustrating problem to deal with!

      The general training approach for dogs with this issue, including Heidi, is to teach them to associate good things with seeing other dogs. This is most often done using high-value food rewards, and marking and rewarding her with a treat every time she sees another dog. The tricky part about this is that you have to start at a distance where she can be successful – meaning that she notices the other dog, but doesn’t immediately lose her mind and start barking and lunging. For some dogs, this means that you need **a lot** of distance at first!

      Once she catches on to the game, she will begin to look at you for her cookie when she sees another dog, rather than getting upset and barking. You can gradually reduce the distance between her and the other dog as long as she is successful, until eventually she can pass another dog on the street while happily taking treats from you instead of barking.

      I’m not sure what kind of training she’s had in the past, but I would definitely recommend trying to find a good reward-based trainer who has experience with this issue in your area, or even a veterinary behaviorist if needed. You can use this website to help you find a trainer: In the early stages, it can be extremely helpful to have someone giving you hands-on guidance. A trainer can also help you set up controlled training situations using a calm, easy-going dog for practice until your girl is ready for real life encounters.

  40. Oh my goodness, great article. My dog Stella (Boxer-x) was always quite shy and nervous, but very friendly as a youngster (I adopted her when she was about 5 months old). Then when she was about 18 months old I put her into doggy-day-care, and because she was so nervous they put her with the small dogs. By Xmas (2013) time she had been expelled as had become aggressive to most of the dogs.

    Since then I have been battling with her dog-fear-aggression. I have tried so many different things -books, videos, avoidance, treats, clickers, dog behaviourists, dog trainers – and very very slowly she is becoming less reactive. It is such hard work.

    She now goes out weekly with a dog trainer and a bunch of dogs for a good run around to improve her socialisation skills. While she still pees everytime he comes to the door, she has such a great time out and about with him! Hopefully one day she will come right, but I think she will always be a fearful girl.

    1. Goodness, yes – it is hard work, isn’t it? Day in and day out! I think it’s hard for people to imagine how much work it is, unless they’ve had a reactive dog themselves.

      I’m glad to hear that your girl is improving, slowly but surely. Patience and consistency can make a huge difference over time in dogs like this, so kudos to you for going the distance with her 🙂

  41. Very interesting article. I have an 11 year old Border Terrier who was attacked when 10 months old and to this day he reacts very badly when he sees any other dogs. I had no idea how to deal with it, went to a worse than useless ‘dog trainer’ who did not/could not help or advise. I wish I had known then what I have since learned and I would have a very different dog today. I eventually found a good training club and my learning continues but all too late for my old boy.

    1. I’m glad to hear that you’ve found some good people to work with! I think that all of us have things that we would go back and do differently with our first dog – learning takes time, and often, as you say, that learning may come too late for our first pup and whatever issues they may have had.

      The good news is that going forward, you can apply everything you know now to make things better for the dogs that come after. And I’m sure your old boy appreciates your knowledge now as well, even if it may not be as life-changing for him as it might have been years ago.

  42. Thank you for a great article! There is a closed FB group worth joining- Nail Maintenance for Dogs- that is very helpful.

    1. Thanks very much for the info – it’s always good to know where to find resources for nail trimming issues! 🙂 It looks like a great group.

  43. I know exactly what you are talking about. At 9 months my friendly puppy was attacked while we walked through on neighborhood. Now every time a dog is coming toward him he starts to bark like crazy. Again at 11months, last week, we were at the dog park and a 5 yr old female gsd rolled him after bathing like crazy at him before entering. The owner tried to say she was putting him in his place. I was so mad as the owner allowed this to happen twice without stopping his dog. I had to do that. Then I let. What if this had happened at the vets office?? Why do people allow ride dogs to do this?

    1. I definitely share your frustration! It really is a shame that so many owners do a poor job of controlling their dogs, and allow them to run up to and harass yours – this certainly doesn’t help things when you have a dog who is already fearful and reactive.

      Many of these people are perfectly nice and well-intentioned, just oblivious to the harm they may be causing. Trying to educate dog owners about these issues is our best bet for improving things over time.

  44. Thanks for a thorough and informative post. Until a few months ago when I attended a rescue seminar, I had never heard of the second “fear” period in young dogs. It helps explains a 10-year-old (to me) mystery as to why my older labradoodle, shortly before she turned two, basically overnight, went from a happy-go-lucky typical lab-type temperament to a nervous, skittish girl, terrified especially of any kind of loud noises suddenly sounding behind her, unsure around other dogs and sometimes even people. Unfortunately I don’t know what happened to cause the behavior turnaround, and have learned to deal with her issues over the years.

    1. I forgot to mention — my girl was a puppy mill rescue, probably about 4 months old when I got her. She had never even seen grass; she was terrified the first time I took her out into the back yard. Despite that beginning, as I said, she seemed to be well adjusted until the fear set in a bit before 2 years old. She would not bite someone unless she had a strong fear reaction — but I have no doubt there are situations in which she would bite. So I’ve just always been extremely careful about monitoring her surroundings and trying to keep her calm and focused on me when she starts getting really fearful.

    2. This same thing happened with my GSP shortly after he turned a year old.. He went from mr confident loving everyone to skittish around people. He was confident in the show ring as well as in the field and loved meeting people.. then it was just like someone flipped a switch and we have no idea what happened. We have been working through it the past year and he is better but not like he was by a long shot.

      1. Very frustrating – I can sympathize! It sounds like you’re doing a good job of working through it. Sometimes it can be hard to put your finger on exactly what may have frightened them, but I would agree that the timing and suddenness of the behavior change is very suggestive of a negative experience during this sensitive period. The good news is, we don’t need to know exactly what happened to be able to treat it effectively – so I’m glad that your boy seems to be improving!

        1. He is improving but is still far from being back to the confident boy that he always was.. It has been a slow process.

    3. Yes! It seems that the second fear period is less well-known – most owners realize that bad experiences as a young puppy can be really detrimental, but it can be a surprise to find out that there is a second sensitive period during adolescence. Sometimes a negative experience like this may be so minor that we don’t really even notice or remember it, but it can leave a lasting impression on your dog if it happens at just the wrong time.

  45. So the question is how do you break the bad trait / habit /fear that triggered a behavior change at almost 7th months of age when the dog is now 2.

    1. An excellent question! 🙂 I’m actually going to be doing a post on that very topic shortly, so stay tuned!

      The short answer is, you teach your dog to associate good things with whatever it is that triggers the aggression – usually very tasty treats, although there are other options for dogs with food allergies or who aren’t very food-motivated. It’s important to do this slowly and carefully, starting at a distance where your dog is comfortable and then gradually moving closer as long as things are going well. The concept isn’t tricky, but the logistics of doing it properly can be challenging sometimes.

  46. To touch on an important point…very bad experiences that happen to dogs through their entire puppy-hood or early adolescent stages can also be detrimental to their future behavior as an adult, not just during their “fear periods”. This is very important for everyone to understand.

    1. This is certainly true! A negative experience at any time in life can have an impact. But this impact will be significantly greater, all things being equal, if the experience occurs during one of the fear periods.

    1. Hey there! Thanks for bringing it to my attention. I’ve had a look at the page, and she did give me credit as the author and linked back to my site as the original source, so I think that’s very reasonable. It’s always interesting to see how far my articles travel! I have a reader who translated this one into French as well, I believe.

      Thanks again for pointing it out to me, and glad you’re enjoying the blog 🙂

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