www.danielwillingham.com/daniel-willingham-science-and-education-blog/the-debunking-of-hart-risley-and-how-we-use-science
The "Debunking" of Hart & Risley and How We Use Science
Daniel Willingham
The recent kerfuffle concerning Hart & Risley (1995) and the 30 million word gap offers an object lesson in science, the interpretation of science, and the relation of science and policy.
Let’s start with the new science. Douglas Sperry and colleagues sought to replicate Hart & Risley, who reported the 30 million word gap—that’s the projected difference in total number of words directed to a child by caregivers when comparing children of parents on public assistance and children of parents in professional positions. Sperry and his team claim not to find a statistically reliable difference among parents of different social classes.
Coverage from NPR made it sound like Hart & Risley had been debunked, with the headline “Let’s stop talking about the 30 million word gap.”
But the Sperry report doesn’t really upend Hart & Risley.
First, Sperry et al. claim that the Hart & Risley finding has never been replicated. I am not sure what Sperry et al. mean by “replicate,” because the conceptual idea that socioeconomic status and volume of caregiver→child speech has been replicated. (The following list is not offered as complete—I stopped looking after I found five.)
Gilkerson et al (2017)
Hoff (2003)
Hoff-Ginsberg (1998)
Huttenlocher et al (2010)
Rowe (2008)
None of these is an exact replication---they have variations in methods, population, and analyses. The same is true of Sperry et al
......................
templeinfantlab.com/wp-content/uploads/sites/2/2018/09/GolinkoffHoffRoweTamisLeMondaHirshPasek2018.pdf
"Language Matters: Denying the Existence of the 30 Million Word Gap has Serious Consequences"
Argues for the importance of retaining focus on the vital ingredient to language learning—quality speech directed to children rather than overheard speech, the focus of Sperry et al.’s argument.
There is little question that the language addressed to children matters for language development per se and for all its collateral benefits—for acquiring informationabout the world, developing self regulation skillsand executive function, and engaging with teachers and peers. Overhearing language about death and taxes—topics of interest to adults—can never be as effective for language learning as participating in contingent conversations about what matters to children.