People tend to dumb dogs down. They are thrilled to have a 5 word vocabulary - come, sit, down, stay, heel. If you only had a 5 word vocabulary with your best friend it would be a very short phone call, and you wouldn't have a very deep relationship.
Dogs are capable of SO MUCH MORE!!!! And your own dog probably knows way more than you think! We say that 30-40 words is the tip of the iceberg. There is a dog out there with a 1000 word
vocabulary and he can read! Of course its a Border Collie, but it certainly shows us what they are capable of.
Every action your dog can perform should have a word and hand-signal of association. Remember you are not teaching your dog HOW to sit, lay down, run towards you - they ALREADY KNOW HOW to do it all. You just have to create the action and give it a word and hand-signal of association AND be consistent. You can speak English, your partner can speak Spanish and your kids can speak French. The dog will not be confused. He is reading your words, your body language, hearing your tones and seeing the pictures in your mind. Lots of info for him to pick up on. In fact as much as we talk about a big vocabulary, we had a dog (Cowboy passed 2 yrs ago) who just had 1 word - Dog. But 'Dog' meant: come, down, get the horses, leave it, etc. He heard the word but read everything else about us to infer its meaning in that heartbeat.
Every toy in your dogs toy box (at least a dozen) should have a name, and every room in the house has a name. Even the car...get in the 'car', ride 'shotgun', get in the 'back', and get in the 'way back' - the car has 4 different different words.
We always provide a 40 word list for our clients to aspire to, but I love it when clients bring us a list and it far exceeds ours!
The next factor is the levels at which you can count on your dog to perform these words.
Level 1 - inside the house.
Level 2 - outside your front door (not at the dog park - which is Level 3 & 4 combined) where your dog gets an adrenaline rush from the sights, sounds and smells so it is tougher for him to concentrate, but you practiced in the house first so Level 2 will be easier.
Level 3 - at long distances. How good is your dog at 5 ft., 10 ft., 100 ft. away from you.
Level 4 - distractions. How good is your dog around cats, squirrels, other dogs, people, kids, balls....
AND there are levels within levels. I can have cats in the house, or long distances in the house, I can have squirrels in the trees 40 ft. away. These are ways to test your dog at higher and higher levels.
The other part of this picture is that is is great to have a big vocabulary but you have to use it! We all get lazy and start to take things for granted. If you speak a second language you need to keep practicing it to stay fluent. Your dog needs to keep working his whole vocabulary to keep it fresh. You could also make it a goal to teach him something new every week. It helps to keep your relationship in top form and keep you connected.
And yes, Marko, we use Swahili with our dogs just to prove a point.