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Animal Behavior

Why Your New Dog Is Not as Smart as Your Previous Dog

People often believe their first dog was more intelligent than its successors.

Key points

  • Individuals are often disappointed with the intelligence of a new dog in comparison with their first dog.
  • This phenomenon is called "Second Dog Syndrome" or "Survivor Dog Syndrome" [SDS].
  • Persons who get a second guide dog are twice as likely to return it to the training facility as a poor worker.
  • Unfortunately, second dog owners assume the new dog comes with the same level of knowledge as their first dog.
Gustavo Fring/Pexels
Gustavo Fring/Pexels

All dogs are not created equal. They differ not only in their physical appearance but in their behaviors. Some dogs are simply more intelligent, more affectionate, and more easily trained than others, and this becomes quite clear when a person who currently has an adult dog in their household or who has recently lost a dog brings a new dog into their home, especially if that new dog is a puppy or a juvenile. Comparisons between the new household member and its older or deceased predecessor are inevitable and unavoidable.

As an example, I was waiting for our club’s beginner’s obedience class to begin and watching a woman working with a handsome young field spaniel. The woman had trained her previous field spaniel with us, so I was surprised to see how little control she had over this young dog. She finally turned to me and said, “Emma may look pretty, but she doesn’t have half the smarts that Kahlúa [her previous dog] had. She is really frustrating me!”

We still had a bit of time before class was scheduled to begin, so I offered, “Let me give her a whirl.”

My mobility is not what it used to be; however, I took Emma’s leash and gave her an introductory pat and a treat. Then, using lure training (thank you, Ian Dunbar), I spent the next eight or nine minutes teaching the dog the three basic positions: sit, down, and stand. By the time that little session was finished, Emma was responding not only to the lure but also to the verbal commands. I handed the leash back to her owner and said, “I think that she is a bright, friendly, and biddable little girl. Just keep working with her.”

Emma’s owner looked a bit skeptical as she moved to the side of the room and watched the other students and their dogs get ready for class.

A Second Dog Is Likely To Be Perceived as “Second Best”

As I later thought about this incident, it occurred to me that I had seen this pattern of behavior many times. In my experience, a second dog is frequently compared by its owner to the first one and often doesn’t quite come up to what the owner’s expectations might have been. If this is really a common occurrence, then the problem doesn’t actually reside with the dog but with its human owner. If that is the case, then, I reasoned, there should be some psychological research literature that could shed some light on the issue.

It was a difficult literature search; however, I ultimately came across some research conducted by Janice Lloyd of James Cook University in Australia and her associates. This group of investigators was looking at the complexities of successful and unsuccessful matchings of guide dogs to visually impaired people. A mismatch between an assistance dog and a client is a large problem. First, it results in reduced independence for blind people who feel that their guide dog has behavioral limitations. There are emotional consequences with a feeling of lost support since the new dog is not bonding with them. However, there also are financial implications. If an assistance dog is returned to the training facility because it seems unable to work with the client, this represents a considerable waste of resources. It can cost up to $50,000 (USD) to raise and train an assistance dog.

What these researchers discovered was that a second assistance dog was nearly twice as likely to be returned as a mismatch for behavioral reasons or limitations as was the first assistance dog assigned to individuals. This does not appear to be a problem specifically with the dog since the vast majority of these returned dogs were later reassigned to a new home where they were able to continue doing their valuable guidance work with no problems. The investigators named this phenomenon the “Second Dog Syndrome” [SDS].

Second Dog Syndrome Appears in Companion Dogs as Well

More recently, Mikayla Disanayake of the Faculty of Medicine at Monash University in Australia and a team of researchers were able to show a similar phenomenon (where the qualities and abilities of a second dog are undervalued) is also present in companion dogs. They further found that the effects applied whenever a new dog is added to a household that currently has an adult dog in it or if the new dog is a replacement for a dog that has recently passed away. The new dog is seen as less intelligent, more difficult to train, and often not as affectionate or attentive compared to the first or older dog. They suggested redefining SDS as the “Successor Dog Syndrome” since it seems to be the case that the new dog is almost always viewed as “second best” when compared to the qualities of the previous dog, whether this new canine is a second, third, or fourth dog.

Are First Dogs Really Wonderful?

The truth of the matter is that the problem lies not in the qualities of the new dog but rather in the psychology of the owner. Your first dog is just that: your first canine companion and your only dog at that time. The bond you form with them is likely to be intense, and since they are your only pet, you are going to be more compulsive about your training and more attentive to your dog.

When you introduce a second dog, or a successor dog, into your household, you are bound to forget all of the time and effort it took to raise a puppy correctly. So there is a high probability that when a second dog joins the household, you have the expectation that they will behave the same way as the existing or previous dog in your home did. That means that you end up giving the new dog the same freedoms that the older dog had, with the expectation that they will behave correctly. You are also likely to be more casual in your training because you have the implicit belief that you are dealing with an animal that already knows what is expected of them. This is a recipe for disaster or SDS.

Why the Second Dog Is Undervalued

If there is another dog living in the household, your second dog has the first dog to learn from. Because of that, rather than developing a strong working relationship with you, the dog will develop it with your first dog. If you are inattentive, you will find that you are dealing with a pack of two, and you are an outsider. So if you call the puppy, don’t be surprised if he looks to dog number one to see if he should move or not.

If dog number one is no longer living in the house, the comparisons you are apt to make are against the often positively biased memories of your first dog. You must remember that the new dog will come to your home without the benefit of the experience that your other dog had developed over the years that they lived with you. The new dog will not have learned the routines of the household, and you will be frustrated because you will continually be caught expecting a new puppy to be perfectly behaved from the outset. The reality is that the successor dog is not less intelligent or less trainable, but rather that you have forgotten all of the work that you put into your previous dog. The new dog in your household will need the same kind of time, effort, and training to become that “once-in-a-lifetime” special dog that your first dog was.

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.


Lloyd, J., Budge, C., La Grow, S., & Stafford, K. (2016). An investigation of the complexities of successful and unsuccessful guide dog matching and partnerships. Frontiers in Veterinary Science, 3, 114.

Disanayake, M., Howell, T.J. & Oliva, J.L. (2023). From Puppy Love to Pet Peeve: What Causes Second/Successor Dog Syndrome in Assistance-Dog Handlers and Companion-Dog Owners?, Anthrozoös, DOI: 10.1080/08927936.2023.2232660

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