For many years, Hart and Risley’s (1990) “30 Million Word Gap” Study conclusions were foundational research pointing to the importance of preschool learning for student success.
However, more recent research has called their long-standing conclusions into question over the last decade. Objections were voiced about the small sample size in the Hart and Risley study.
What was the 30 Million Word Gap?
In the 1990s, Betty Hart and Todd Risley studied the amount of language heard in the home for children from birth to age 3. Their work studied 42 families from 3 different socioeconomic levels.
Their study aimed to identify how much language each group of students heard in their respective homes during the preschool years.
The researchers tracked 13 wealthy, professional families, 10 middle-class families, and 13 low-income families. Six of the families in the low-income group received public financial assistance from birth to age 3.
During their work, Hart and Risley gathered 1,300 hours of observational data about the language children use in each home environment.
Their study tracked the type of oral language and vocabulary experiences each child heard in the home during these critical early years.
The Findings of their Study
Hart and Risley’s work (published in 1995) identified a 32-million-word gap between children from professional families and children from low-income families.
Hart and Risley reported, “By the time the children were 3 years old, trends in the amount of talk, vocabulary growth, and style of interaction were well established and clearly suggested widening gaps to come.”
According to their data analysis, by age 3, children living in professional families had a recorded vocabulary size of 1,116 words with 310 average utterances per hour.
Children in working-class families had a recorded vocabulary of 749 words, with 223 average utterances per hour.
Low-income children had a recorded vocabulary size of only 525 words and 168 utterances per hour.
Researcher Conclusions
Hart and Risley stated that their research explained why some children come to kindergarten with a wealth of literary experience and a strong vocabulary while others have a limited vocabulary and lag far behind their peers even from the first day of school.
The researchers concluded that “a linear extrapolation from the averages in the observational data to a 100-hour week shows the average child in the professional family with 215,000 words of language experience.”
They noted that the average child in a working-class family heard 125,000 words. Children in low-income and welfare families heard only 62,000 words of language experience during the same period.
In a year, this is a difference of 11.2 million words for a child living with professional parents compared to only 3.2 million words for a child living in a low-income family.
The difference over three years in words heard in the home would be 45 million words for the child in a professional family versus only 13 million words for the child living in a high-poverty family.
Thus, they identified an estimated 30-32 million word gap between the different groups by age 3. Their findings impacted early childhood education efforts and spurred calls for substantial investment in it.
Conclusions Come into Question
Recent efforts by researchers Douglas Sperry, wife Linda Perry, and Peggy Miller (2018) attempted to replicate Hart & Risley’s work to some degree.
While their study was not an exact replication of the Hart and Risley study, Sperry and colleagues could not find any significant differences in the amount of language heard by children in families with different socioeconomic levels.
While Hart & Risley had live observers in the home, the Sperry study used a more unobtrusive recording system to capture conversations within each family.
One theory explaining the difference in outcomes between the two studies is that parents and children may respond differently when live observers are present in the home.
Sperry also theorized that the Hart and Risley word gap study may have had a cultural or racial bias that undervalued or misinterpreted speech activities in diverse families.
Questions Still Remain About Preschool Language Development
Since this time, several other researchers have studied different aspects of early language development and have defended the conclusions of the Hart and Risley study.
A 2017 study by Gilkerson and colleagues using automated recorders tucked into children’s clothing found some similar – but not identical – gaps in early language experiences, as did the Hart and Risley study.
A sticking point, however, is that none of the studies conducted since 1995 used the exact same methodology as Hart and Risley’s work.
Although some researchers criticize the Hart and Risley study because of the small sample size, their work has not been entirely refuted.
More research is needed. We all need to understand why some children have a more extensive vocabulary when they reach kindergarten than other children so we can address these word gaps.
The Importance of Early Childhood Support Still Remains
There is little doubt that there are still vast inequities in American society and the education that children from different racial and socioeconomic backgrounds receive.
While it is unclear whether there is really a 30 million-word gap between preschoolers entering our classrooms, gaps in the word knowledge that children bring to school are still very clear for teachers.
Whether or not the Hart and Risley study had flaws, investing in early childhood education is still vital.
This is evidenced by many other studies on this topic and the success of the Perry Preschool participants. The program produced multi-generational effects on their young participants.
Children need support and the advantages that early learning can provide so they can come to the kindergarten door prepared for learning and success.
Learn more about effective reading instruction in my book, The Threads of Reading: Strategies for Literacy Development
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