However, when we test for language in other animals, we do not test for these underlying cognitive abilities. Rather, rather, we test for the animals ability to express these facilities through some communication system with other animals (either in the same species, or with humans).
It is conceivable to have an animal that has all of the cognitive abilities we associate with language except the ability to serialize/deserialize [0] it. While this ability is significant at the species level, it does not seem like it would be particularly significant at an individual level.
Further if you take the view that language was evolved primarily as a tool for thinking (rather than a tool for communicating), this possibilities seems even more likely. Under this view, we would first develop the cognitive aspects, then develop the communicative aspects on top of them (in the same way that we evolved our "speech organs" on our digestive (tongue) and respiratory (lungs/airway) ones.
It also seems plausible that it was this adaptation that allowed humans to pass the singularity point necessary to reach modern society (which grew up very quickly on an evolutionary timeline). If this were the case, then I would expect to see that the rest of the cognitive abilities associated with speech are actually present and similar in related species.
[0] Our current model of human language is that of a tree. We do not see processes that act on a linear structure until we get into phonology.
It's not. That's why I said that any good theory is going to have to account for all the sentience in the world that doesn't talk to each other.
Secondly, my point is that other animals may still have "language", but just without the small components necessary for communication. If this were true, then language could still be the explanation for consciousness.
I don't agree. Many other types of animals have rudimentary languages, but I wouldn't dispute the sophistication of human language towers above all others, that in itself rests (along with other uniquely sophisticated behavioural endowments) upon what really differentiates us which is the capacity for imagination and abstract thought. The capability to imagine things that aren't actually real, but perhaps could be. It's thought that the seat of all this is the frontal cortex but I see now on wikipedia that is contentious these days [0]
[0] https://en.wikipedia.org/wiki/Frontal_lobe#In_other_animals
https://www.amazon.com/Adams-Tongue-Humans-Made-Language-ebo...
A single outlying data-point hardly disproves a theory, and even so, you can't possibly know that the monkey knew what he was doing. It could just be mimicry. Your thinking about what the monkey is thinking is distinctly the distinguishing trait of human psyche I'm talking about.
EDIT: Also relevant. Operant theory can explain seemingly "intelligent" behaviour as random or observed and mimicked actions that are then reinforced by the environment [0]
Your monkey's behaviour could be explained in a similar vein to that which explains "cargo cult" behaviour [1].
Now, you could say that this is indeed "intelligent" behaviour, but then again a dog can be trained to open a door, and pigeons can be trained to orient themselves based on a clicker [2]. But what I'm talking about here is what distinguishes human intelligence from other forms of life on this planet.
[0] https://en.wikipedia.org/wiki/Operant_conditioning#Origins_o...
[1] https://en.wikipedia.org/wiki/Cargo_cult#First_occurrences
But computers are nowhere near being able to have conscious thought. So what's the difference? Clearly it's not just natural language that differentiates the conscious from the unconscious.
Taking it further, i would argue that whatever physics theory that claims to state the truth about the Universe and its origins has to explain how consciousness works down to the elementary level. Similar how electronic circuits can be explained based on the atomic model and quantum theory. Like a "Quantum theory of consciousness" or some such.
Theories in physics has always been useful even though they are incomplete to this day.