The Word Gap
Hart, who died in 2012, and Risley, who died in 2007, had also identified important differences in kinds of talk. In the recordings of the professional families, they found a “greater richness of nouns, modifiers, and past-tense verbs,” and more conversations on subjects that children had initiated. Catherine Snow, a professor at Harvard’s Graduate School of Education, who studies children’s language development, told me that these findings made sense, since quantity was often a proxy for quality. “Families that talk a lot also talk about more different things,” Snow said. “They use more grammatical variety in their sentences and more sophisticated vocabulary, and produce more utterances in connected chains.” Such parents, she noted, “don’t just say, ‘That’s a teapot.’ They say, ‘Oh, look, a teapot! Let’s have a tea party! There’s Raggedy Ann—do you think she wants to come to our tea party? Does she like sugar in her tea?’ ” Parents who talk a lot with their young children ask them many questions, including ones to which they know the answer. (“Is that a ducky on your shirt?”) They reply to those devilish “Why?” questions toddlers love with elaborate explanations. Erika Hoff, a developmental psychologist at Florida Atlantic University, has published studies about early language development whose results are similar to those of Hart and Risley. She recalled marvelling at “the young professor mothers” at a university childcare center: “Everything was a topic of conversation. If they had to get out of the building in case of a fire, they’d be so busy discussing the pros and cons with their toddlers that I kind of wondered if they’d make it.”
Hart and Risley's study is really fascinating, but it doesn't provide a quick fix to the word gap. Ultimately, the program The New Yorker article discusses -- Providence Talks -- is coaching parents on parenting, not just words.
You can read more about Providence Talks here: Talk to Your Kids - The New Yorker.
I also recommend reading Selling the Language Gap for a different perspective.