..or almost an equal size to the first one
Personal opinion on my part and I have no resource to back it up.
Part 1, yes I think that's just an "old country saying."
Part 2. Much of the answer depends upon how being smarter is defined. If we define being smarter by how much knowledge the brain holds, then those people who can memorize books, facts, trivia, and that kind of thing certainly rate high on the scale. On the other hand, if we define being smarter as the ability to reason, some people can reason through problems they encounter daily and events of the times so they rate high in that respect. Then there are those who hardly know what's going on today but have the vision to put things in their proper place for tomorrow. They visualize how things can be improved and often their ideas are quite innovative. Finally we have those people among us who are extremely observant; they see what most of us miss in daily life. They can seize on the unexpected and turn it to benefit mankind. I call those serendipitous people. Alfred Nobel (of the Nobel Prize family) was one of those and I'm speaking of the his work with dynamite. I don't think anyone knew how Einstein's brain worked. Remember that he could reason through the toughest equations by just thinking about them but had trouble remembering his telephone number and where he lived. Some people called him a crack pot but he was a great thinker.