A verbal animal would probably also need a reason to talk about the unpleasantness of one's mate, for instance (its mate, not your mate). — Bitter Crank

Or more than that, the animal would have to have the capacity for grammatical construction.

Words are one thing. Animals can learn hundreds of them. Rules of recursive sentence structure are a different matter. What Koko and all the other experiments show is no non-human develops the grammatical fluency which is part of human biology.

So you don't need to have a reason to talk. But you do need grammatical capacity to be able to speak in reasoned fashion.

I watched a program about Koko on PBS recently, and in it, [it was claimed] she frequently asked for visitors (among other things). I don't think it would be all that difficult to determine if she is only imitating, or if she is asking on her own..... but I'm not a scientist.

Going on rather old memory (30 years back, at least) what Koko's handlers were looking for was combinations of words that were novel. They kept track of what they had taught her, so knew when she was repeating what she had learned, and what she was generating from scratch. She might have learned "want" and "visitors" in very separate sessions, ad might not have ever heard those two words used in combination. If she saw "visitors" nearby, initiating the phrase "want visitors" would be language generation. Not very complicated but... language none the less.

It seems to be the case that primates possess very limited language ability, but how much, how little, isn't settled. Some primate specialists doubt that Koko generated anything spontaneously.

Humans do both -- imitate and generate speech. Baby humans spend quite a bit of time learning how to generate sound -- baby talk. They don't generate "ma ma" or "pa pa" without having sounds, words, and meanings, modeled for them. Eventually they go beyond imitation to generation. Then they won't shut up.

It seems to me that if Koko did anything like some people are saying she does.... then some legitimate researcher would be all over it, and there would be a ton of research papers on the subject. (absence of evidence anyone?... lol).

Hmmmm. I suppose I'll just have to wait and see.

This is the program I was referring to. It was broadcast for the first time earlier this month.

I just want to point out that besides our ability to form language, we also have the capacity to manipulate every physical thing that we can touch. We manipulate them not only slightly, but vastly, and turn the molecules from one form into a completely different form. Animals have the capacity to manipulate matter, but they do not generally manipulate everything that they find, and they do not manipulate it to the degree that allows for such a vast difference from one state to the next.

In other words we are the only species that builds cars and planes and trains and boats and rubber ducks.