The result of their research was a landmark study published in 1995, which maintained that a typical child whose parents are highly educated and working professionals is exposed to roughly 1,540 more spoken words per hour than a typical child on welfare. Over time, they concluded, this word gap snowballs so much that by age 4, children in rich families have been exposed to 32 million more words than children in poorer ones.

The study was a sensation, with the media and policymakers fixating on the so-called “word gap” as a key source of longer-term academic disparities between poor and rich kids. It was immediately embraced by academic researchers, and was cited in more than 7,000 academic publications. It influenced welfare initiatives, government pilot programs, and grant campaigns. The Obama administration championed efforts to close the “word gap,” organizing a campaign to raise awareness of the issue and to encourage parents to talk more to their children.

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