There's a word for those who cannot learn to read and write their native language: illiterate. But, up until now, there has been no word for those who, though vocal, cannot learn to speak their native language.
We have, in George Bush, a perfect example of one who is vocal but has not learned to speak his native language. Listening to Bush's bleatings, mumblings, stumblings and bumblings is to hear the psychopath's atempt to mimic human speech in order to fake an appearance of normality. This copy-cat approach of imitating the sound and sequence of words at random has been spectacularly unsuccessful, and Bush is unaware that his blathering is incomprehensible.
The term "to bush" will enter the lexicon to mean the spouting of nonsensical gibberish while the spouter's sycophants nod in feigned understanding. Bush, himself, will come to represent in one generation, an evolutionary regression of several hundred thousand years to his pre-literate but vocal primitive ancestors.