Intelligence is generally correlated with the size of their vocabulary thought.
This is obliviously just a rule of thumb but if you take a pool of 100 well spoken individuals and 100 ... Not well spoken and then give them all some kind of intelligence test, the first group will definitely score significantly higher then the latter.
Yes, I'm aware that non native speaker (I am one of these), but they'd be statistically irrelevant in the context of the general population
This is obliviously just a rule of thumb but if you take a pool of 100 well spoken individuals and 100 ... Not well spoken and then give them all some kind of intelligence test, the first group will definitely score significantly higher then the latter.
Yes, I'm aware that non native speaker (I am one of these), but they'd be statistically irrelevant in the context of the general population