the research of Hart & Risley has shown that over half of the variance in a child’s vocabulary at age 3 can be attributed to the ways in which a parent talks to their child, and the way parents talk to their children varies dramatically depending on socioeconomic status. Specifically, they estimate that by age 4 the children of professional parents have been exposed to about 45 million words, whereas the children of welfare parents have been exposed to only about 13 million words. This means that by the time children are 3 years old, parents in less economically favored circumstances have said fewer different words in their cumulative monthly vocabularies than the children in the most economically advantaged families in the same period of time.