There is a well-known story about this discussed in Radiolab [2010] https://radiolab.org/podcast/91725-words/transcript
Here's ChatGPT summarizing one section:
> Younger signers had developed a richer vocabulary for mental states—concepts like believe, remember, forget, understand. They were much better than the original older signers at tasks requiring them to reason about what another person thinks or knows. Later, as the older signers picked up those mental-state terms from younger people, some of them improved on the same tests. Senghas describes it as language giving them new insight into other people’s thinking and motivations.
I see several likely stories:
* Much animal communication is practical, descriptive of the present (nothing abstract, or very few abstract concepts)
* If a species could expand its communication, it would give it more powerful tools and allow for more meaningful conversation with humans
* If such a thing is possible, it will be extremely disruptive to that species
I think if you could communicate about abstract ideas with your dog, you could exchange bedtime stories. However, I don't think such a thing is possible today, and it's not clear what species (if any, besides humans) will, in fact, be able to learn such things
I don't think it's particularly controversial to say "written language is a meaningful technology advancement for a civilization", though!
They're pretty damn interesting. Cats sometimes think hard about their responses. And they use metaphors. And express emotions.
There's always the suspicion this is a fake marketing exercise. But if it is, it's a very ornate and extended one.
I have no idea how we're supposed to communicate with aliens if we can't communicate with other mammals.
"They're really stupid and can't do calculus or invent FTL travel" isn't much of an excuse.
Except when we do, but it doesn't make for flashy press releases. Pet owners, vets, farmers throughout history - anyone who lives alongside animals, cares for them, and is open to developing an emotional relationship with them, knows animals are more than just small finite state machines made of meat. But it takes time to spot and learn the patterns of behavior, and as I said, it's a two-way street; the animal has to "open up" and learn you as much as you have to learn them.
It is a kind of thing that's difficult to cleanly verify and reproduce, and it's also kinda mundane. The cases that made headlines look like Clever Hans the other commenter mentioned.
I imagine that a better classifier, some general AI system that gets to learn and observe the animals, would be able to tease out the patterns and then translate them to English, and then that would be reproducable and make for flashy headlines.
The real lesson we should have learned is that horses are stupid and we should have been testing a Border Collie.