There is a saying that you can't teach old dogs new tricks. When it comes to canine behavioral problems, age is only one factor that can predict how well a pet may respond to clinical intervention. In a paper published in Frontiers in Veterinary Science, researchers provide the first evidence on the importance of not just a dog's age, sex and size on treatment success, but the owner's personality and the kind of bond that human and animal share.
source https://phys.org/news/2021-01-highlights-factors-success-canine-behavioral.html