Brooks, David (2011-03-08). The Social Animal: The Hidden Sources of Love, Character, and Achievement (p. 13). Random House, Inc.. Kindle Edition.
Geoffrey Miller notes that most adults have a vocabulary of about sixty thousand words. To build that vocabulary, children must learn ten to twenty words a day between the ages of eighteen months and eighteen years. And yet the most frequent one hundred words account for 60 percent of all conversations. The most common four thousand words account for 98 percent of conversations. Why do humans bother knowing those extra fifty-six thousand words?