I'd like to know the precise meaning of "improving his mind" in this excerpt from the last chapter from The Great Gatsby by F. Scott Fitzgerald. Usually to improve one's mind means to cultivate one's mind; but the following remark of Gatsby's father about the way he ate suggests that the phrase includes the behaviour, the good manners.
"Jimmy was bound to get ahead. He always had some resolves like this or something. Do you notice what he's got about improving his mind? He was always great for that. He told me I et like a hog once and I beat him for it."