There are likely some differences between ethnic groups, but those who are better-educated do tend to have better vocabularies. Children in higher-class households are often asked their opinion more often. I believe the Kennedys were required to report about something that had happened in the news every night at dinner. Social scientists have watched mothers interacting with their young children and have noted quite a bit more describing going on with higher-class white women. I don’t think you can go by wealth as much as by class, although there are some newly wealthy people who think that, because they have money, they have more right to talk. There are also some upper-class groups (Boston Brahmins, for example) who are traditionally terse.