[recursive]

I don't think unique-words/total-words can be used directly as a metric for intelligence of lyrics. In any body of text, I'd expect that ratio to go down as total-words increases. For some extreme example, if there is one total word, then the ratio is 1.0. If there are infinitely many words, then the ratio is 0.0. That doesn't really say anything about how intelligent they are. Without knowing anything specifically about it, I'd expect unique words to roughly scale logarithmically with total words for a constant "intelligence", whatever that means.