For many years, the conclusions of the “30 Million Word Gap” Study by Hart and Risley (1990) was foundational research pointing to the importance of preschool learning for student success.
However, during the last decade, their long-standing conclusions have been called into question by more recent research. Objections were voiced about the smallness of the sample size in the Hart and Risley study.
What was the 30 Million Word Gap?
In the 1990’s, 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.
The objective of their study was 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. The final group was 13 low-income families. In the low-income group, six of the families 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 used with children in each home environment.
Their study tracked the type of oral language and vocabulary experiences that each child heard in the home during these critical early years.
The Findings of their Study
As of result of their work (published in 1995) Hart and Risley identified a 32 million word gap between the children from professional families and the children from low-income families.
Hart and Risley reported, “By the time the children were 3 years old, trends in 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 the working class families had a recorded vocabulary size of 749 words with 223 average utterances per hour.
Low income children had a recorded vocabulary size of only 525 words with only 168 utterances per hour.
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 the low-income and welfare family environment heard only 62,000 words of language experience. during the same time period.
In a year, this is a difference of 11.2 million words for the child living with professional parents while 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 early childhood education.
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 in their study were not able to find any significant differences in the amount of language heard by children in different socioeconomic level families.
While Hart & Risley had live observers in the home, the Sperry study used a more unobtrusive recording system to capture talk that took place in each family.
One theory for the difference in outcomes of the two studies was 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 did Hart and Risley in their work.
Although some researchers criticize the Hart and Risley study because 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 larger vocabulary when they reach kindergarten than do 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 whether or not there is really a 30 million word gap between preschoolers coming into our classrooms, gaps in the word knowledge that children bring to school is still very clear for teachers.
Regardless of whether or not the Hart and Risley study had flaws, the importance of investing in early childhood education is still vitally important.
This is evidenced by many other studies on this topic as well as 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 in life.
Learn more about effective reading instruction in my book: The Threads of Reading: Strategies for Literacy Development
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