I have owned six dogs in my life, most recently getting a 7 week old pup staffy x ridgeback, now 16 weeks old. He goes with our 9 year old girl staffy, who can follow conversations, eg planning to go to the park or beach without directly mentioning it in any way.

All my dogs have understood a lot of words, some more than others, but all way more than 20.

The aspects that promote this, I believe, are this:

1. They are treated as companion animals. They live in the house with the humans and generally have full access thru the house.

2. No crating. Maybe if it is some kind of working dog, but a companion animal is a companion, and would you put a companion in a crate 22 hours a day? I don't care if you think that a dog comes to like the crate, I would say don't confuse familiarity with liking it. In what evolutionary precept is crating a thing that ever had any parallel in the wild?

3. You talk to the dog, like it is a human that can't speak. You tell it what you are doing using consistent language. Example, when leaving the house, we tell the dogs what we are doing and how long we will be. eg I am taking J to school, I'll be back soon. Or, I am going to work. Very quickly they learn and know what to expect and anxiety is reduced. I can tell because if I say I'm going to work, they immediately head to their favourite long term day resting spots.if I say I am going to the shops, they know I will be 30-90 minutes and there is a chance I will be returning with treats and hang around the door.
Also just a few times now and then, especially early on, the dog will come with me to, say, drop the child at school, or visit work, so they can see where we go and understand a little better what goes on.

Having the dogs live with as part of the family means sometimes there are problems, eg our pup is currently teething and just can't help himself with items of certain texture. We keep important things out of reach, close bedroom doors when not home and use mistakes a chance to teach. The older dog has never once got into the bin or any other such misdemeanours when unsupervised at home.

I see a lot of people ignore their dogs most of the time, I wouldn't expect such dogs to have strong language skills, but try might. If they are around and a wake, ours are constantly talked to, just telling them what we are doing or what is going on. They learn to associate, often quite quickly.

Also many owners seem to make little effort for language consistency, outside of obedience commands like sit etc.

Living in the house, it's important the dogs are consistently treated in accordance with their position in the pack. What many people think is being kind, is people kind and dog mean. A dog is happiest when it knows its place. The happiness is not related to the level of that place, more the consistency of treatment. A dog confused about its place might instinctively feel the need to challenge for leadership of the pack, that's when people get eaten.

If your dog is looking stressed and uncertain of its place, by challenging you in little ways, you need to do the little things to reinforce its position eg it does not go thru the door before you, it does not eat before you. Maybe you eat and leave a very small amount if food on your plate, which you then give the dog.you admonish any challenge for control, not meanly, but firmly.grasping the muzzle with your hand, not hard, can be enough. When just weeks old, that is what the mother does with her mouth, it is a powerful gesture ingrained almost instinctively.

Pampering a dog is being mean to a dog, treats should be earned not given randomly, that is just confusing.

Just like people, dogs behave the way you treat them.

I learned from an ex military dog trainer who went way further in his work training, but those were special animals trained to cope with crowds etc and in that environment might be called upon to save someone's life one day. But many of the techniques used would shock most people, but make perfect sense when considered in the context of training a pack animal to be a working animal.