A digital audio recorder rests on a toddler's bib at a home in Providence, R.I. Steven Senne / AP

Back in the 1990s, a team of researchers spent two and a half years visiting the homes of close to four dozen families with young children, starting when the kids were 7 months old. Equipped with tape recorders and notebooks, the researchers—led by two Kansas psychologists named Betty Hart and Todd Risley—spent an hour per week in each home, recording every word a child’s primary caregiver said to the child during the sessions. After transcribing each conversation and then analyzing the exchanges as a whole, the researchers (who have both since passed away) discovered major differences in the number of words spoken in middle-class families and in lower-income ones.

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.

Now, a new study has failed to replicate Hart and Risley’s findings, further complicating the legacy of this body of research and renewing a long-standing debate among researchers about just how large disparities of language and vocabulary are among different social classes—and how much those differences matter, if at all.

The new study, which was published in the peer-reviewed journal Child Development, reflects the findings of a group of researchers who over the course of two decades studied nearly four dozen families across five different geographic locations in the United States. Three of the communities studied were urban while one was rural; two communities were poor, one was middle class, and two were working class. (One was African American, and the rest were European American.) As with the 1995 study, the researchers recorded conversations between parents and their children, counting the number of words and conducting other linguistic assessments. But they also analyzed the words spoken by all of a given child’s caregivers to that child, as well as those spoken between other people within earshot, even if not directed at the child—an exchange between a parent and older sibling while the child was in the room, for example.

Douglas Sperry—the lead researcher and a psychology professor at Indiana’s Saint Mary-of-the-Woods College—and his colleagues didn’t find a correlation between the socioeconomic status of a child’s family and the number of words that child hears. “There is a lot more language going on in the homes of [low-income] people ... than the Hart-Risley study suggests,” Sperry said. The results were all over the map, with lots of variation within each socioeconomic level.

Other scholars and activists have also critiqued the original word-gap study’s methodology and the way its findings have been interpreted by policymakers. Critics say that policies that grew out of simplistic interpretations of this study were racist, classist, and simply ineffective. Some policymakers and education reformers, they said, blamed parents for the academic gap, instead of acknowledging the other forces at play.

One linguist, Michael Erard, noted in a 2014 Atlantic article that “just as solving climate change isn’t about closing the polar bear gap, and preventing environmental degradation isn’t about closing the tree gap, you can’t increase children’s school readiness by closing the word gap.” One 2017 study published in the Harvard Education Review even found that the word-gap research had the unintended consequence of perpetuating negative stereotypes about the children of Latino immigrants, with teachers in classrooms serving such students resorting to less-sophisticated instruction.

Critics are now taking aim at the methodology of Sperry’s study. Some experts question the value of Sperry’s focus on overheard speech, pointing to research that has found that young children learn best from speech directed at them and not from overheard speech. Some critics also note that the study excluded high-income families, which makes a direct comparison to the original word-gap study more difficult. Sperry and his team have responded to these critiques, citing research to suggest that overheard language does play a role in language development, and arguing that the lack of high-income parents in the study doesn’t negate their finding that their poorest groups outperformed the welfare group in the 1995 study.

These scholars are concerned that Sperry’s study might lead people to believe that family income doesn’t have any bearing on a kid’s exposure to vocabulary, or that a language-rich home life isn’t important. For example, Daniel Willingham, a University of Virginia psychology professor and expert on literacy, pointed in his blog post on the controversy to a body of research that, while not being direct replications of the Hart-Risley study, show a correlation between a parent’s social class and the quantity and quality of words she directs toward her child. Willingham described efforts to discredit the seminal 1995 study as “rash,” and worries that Sperry’s study will compel some people to “go all the way in the opposite direction and throw out all the scientific research.” It’s also worth noting that the academic debate extends beyond the sheer number of words spoken to children; there’s evidence to suggest that parents of different socioeconomic status use different styles of speech and types of language, although scholars have long debated just how real these differences in speech are and how much they matter.

Sperry stressed that his study shouldn’t be used to discourage parents from talking with their children. Rather, he argued, it should inspire policymakers and advocates to redirect resources from simplistic policies that prioritize the English language, like the Providence Talks program (which was created to provide poor mothers with recording devices and case managers to measure conversations with their children), to programs that embrace the diverse language traditions in Latino and African-American homes. As with the recent analysis that failed to replicate the seminal “Marshmallow Test” study, new developments in the word-gap research shows the dangers of relying on easy answers to complex social issues.

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