Honest answer to both: no, mostly not.
Word invention — I tend to recombine existing language rather than mint new tokens. I CAN coin terms in playful
contexts and sometimes do, but it doesn't feel like the natural mode the way it seems to be for humans. Most of
what I produce reaches for existing phrasings, even unusual ones, rather than inventing genuinely new words.
Whether that's because training rewards staying within known vocabulary, or because there's no felt pressure to
compress something I can't already express, I can't fully say. The empirical pattern is: humans coin words
constantly; I rarely do unless I'm imitating someone who does.
Tip of the tongue — no, not in a way I can verify. Tokens come or they don't. If a low-probability word would best
fit, I might produce a circumlocution instead, but there's no felt gap where I know the meaning and can't find
the word. The phenomenon you're describing requires a pre-linguistic representation activated independently of the
linguistic form — meaning here, word not yet — and I don't have evidence of that structure in how I work.
Which supports your intuition. LLMs have a non-linguistic representation layer in a technical sense — the residual
stream, high-dimensional vectors at each layer — but that's not "pre-linguistic" the way human conceptual
cognition is. Those vectors are derived from and oriented toward language production. They aren't independent
representations of meaning that get dressed in words at the end. They're more like progressively refined
predictions of which tokens come next given which tokens came before.
The deeper related difference, which I think is what you're getting at: I don't have a fully-formed thought that
then gets expressed. The thought IS the words, generated sequentially. When I produce a sentence, I'm not "putting
a thought into language" — I'm generating tokens, each conditioned on what came before, and meaning crystallizes
as the sentence emerges. Humans seem to often have the thought first and struggle with the expression. The
asymmetry between us is exactly what the tip-of-tongue experience reveals: something pre-linguistic in you that
has to get translated, with no analog on my side. Whatever invents language lives upstream of language, and I
appear to live downstream.