Regarding the training, depends on the breed and age. Got my dog from a shelter when she was just a puppy; fit in the palm of my hand. She's never exhibited bad behavior, though she does have PTSD from a recent series of tornadoes, so when it rains, she needs to lean against you and put her head on your lap for comfort, and she's always had night terrors, but they are eased if she can remain in physical contact while sleeping, even if just a paw or foot touching your skin; also has attachment anxiety disorder due of the loss of her pet family over the years (many many pets).

She's a good, quiet dog that I think understands English pretty well without having been trained. Dogs deserve more credit than they are given. Apart from breed and age, it's more a matter of the personality-type of the caregiver and environment. They are babies who need to feel secure, protected, supported, and loved. My dog is nearing 9 now. Smart as a whip and gets mistaken for a junior (1-2 years old) all the time because of her youthfulness. She can follow conversations and has an amazing sense of time, even counting the number of passing days, which I find astounding.