I have been casually experimenting with my dogs’ language abilities for the past 12 years. I have taught them some specific commands of course, but I also speak natural language around them and watch to see how much they might pick up on their own. We are constantly having to use new words or spell certain activities or foods to avoid excitement. My wife and I have to be cryptic around the dogs to keep a secret. They learn real fast. Intonation may help but isn’t an absolute requirement. I can whisper in the next room and be understood. I can string together familiar words and they understand a new context. I once said “Go tell Junior to let you out”. The dog went to my sons room and woofed. I never taught that to the dog. My dogs are Aussies.
Wow. That’s something. My pup picks up a lot in conversation but that’s incredible.