While I’m unaware of any studies that would validate or invalidate the hypothesis, my guess is that the greater one’s linguistic and mathematical abilities, the more connections one is able to discern between seemingly disparate phenomenon and the more subtle and complex one’s thought processes become. Conversely, when the best one can do is use a limited lexicon in an approximate manner, it’s like throwing mud against a wall in the hope that some of it will stick somewhere, somehow. And even if a person with limited linguistic capabilities were to be capable of slightly more sophisticated thought, expression of such thought would be nearly impossible. Therefore if we wish to learn to think, we have to learn to acquire the symbolic means whereby to manipulate and express concepts more complex than “Me want milkshake now.”