You just got a new puppy, and you noticed that he is starting act a lot like the older dog in your house. In some ways it's good, and in some ways it's bad—no dog is perfect, after all.
You're wondering if this is normal. Do puppies learn from older dogs? Do dogs of the same age learn from each other? And, if the answer is yes, can you train two or more dogs to act better at the same time?
By finding out the answers to these questions, you can make your life a lot easier if you're having trouble with dog training at home.
Do dogs learn from other dogs?
The fact is that dogs do learn from other dogs. Dogs teach one another behaviors, whether these behaviors are "good" or "bad." It doesn't matter whether you bring an adult dog or a puppy into your home—the new pup will learn from the one you already have. Group-coordinated behaviors that dogs use to model their behavior after one another are called allelomimetic behaviors.
If you have a new dog in the home, they will learn many things from the dog that has been with you for a while. You may notice that your new dog seems to look up to your other dog. He'll follow your other dog around the house, cuddle with him, and generally mimic his behavior, whether it's positive or negative. However, it can be extremely helpful when it comes to training your new dog and getting him used to your home.
Getting over fears
Dogs can teach one another to get over fears by demonstrating that something is safe. For example, if your puppy is afraid to get into your car, but he sees your other dog do it with ease, he might then follow him into the car.
One of the key components of dog training is getting your dog to go to the bathroom outside. He may be scared to go out or not know that he needs to do his business outside of the home. If your other dog runs outside to pee or poop and/or is eager to go on a walk, then your new dog will be as well.
Sitting and other obedience cues
Let's say you trained your one dog to sit before he gets a treat; your new dog will see your other dog sitting and then do the same. Your new dog may also see your older dog being quiet under the table while you eat and getting rewarded with food, so he'll likely mimic that behavior to get that reward as well. Of course, every dog is different, so it's never 100% sure that the new dog will learn just by watching the first dog. Be patient with your new dog as they are learning.
Learning undesirable behaviors
Dogs can also learn undesirable behaviors from one another. For example, puppies can become possessive of their food and toys if they see older dogs doing the same. If this happens, this is a good time to either call a trainer or commit to doing a significant amount of training by yourself. One dog behaving badly may have been tolerable before, but now that you have two it's become a real problem. (The American Kennel Club has a helpful guide to finding a qualified trainer.)
Training both dogs
Thankfully, allelomimetic behaviors can work in your favor. If you want to train both dogs to behave in more desirable ways, the newer dog is likely to take cues from the more established dog.
Make sure you only use positive reinforcement training, because negative reinforcement does not work with dogs, and can venture into unethical territory. For example, if you're teaching a puppy to go pee outside, then you should say "good boy!" whenever he pees outdoors, and then reward him with a treat he loves. Don't yell at him when he pees inside the home or shove his face into his pee.
If you're trying to teach both dogs to sit before jumping in the car, start with your older one by telling him to sit right before he gets into the vehicle, give him a treat and then tell him "go ahead."
You want your dogs to respect you, not fear you, and positive reinforcement will help achieve this goal.
Dogs can sense human emotions
Dogs mimic humans in some ways as well. If you have a loud, rambunctious, or stressful household environment, then your dog may act in undesirable ways. Dogs are excellent observers of humans—they pick up on our emotions and will often adopt them as their own. Dogs know when we're angry, and it may stress them out. If your dog is suddenly acting in new undesirable ways, take stock of their environment and what has been going on in the household recently. You might be able to make changes to their environment to make it more peaceful, and/or exercise them more and provide them with more mental stimulation.
Dogs do mirror other dogs' behavior, whether it's "good" or "bad" behavior. But with some positive reinforcement training, you can get both dogs to act nicely and have an overall more enjoyable environment at home.