Children whose families were on welfare heard about 600 words per hour. Working-class children heard 1,200 words per hour, and children from professional families heard 2,100 words. By age 3, a poor child would have heard 30 million fewer words in his home environment than a child from a professional family. And the disparity mattered: the greater the number of words children heard from their parents or caregivers before they were 3, the higher their IQ and the better they did in school. TV talk not only didn’t help, it was detrimental.
Hart and Risley later wrote that children’s level of language development starts to level off when it matches that of their parents — so a language deficit is passed down through generations. They found that parents talk much more to girls than to boys (perhaps because girls are more sociable, or because it is Mom who does most of the care, and parents talk more to children of their gender). This might explain why young, poor boys have particular trouble in school. And they argued that the disparities in word usage correlated so closely with academic success that kids born to families on welfare do worse than professional-class children entirely because their parents talk to them less. In other words, if everyone talked to their young children the same amount, there would be no racial or socioeconomic gap at all. (Some other researchers say that while word count is extremely important, it can’t be the only factor.)