Those of us who work in early childhood frequently hear reference to the “30 Million Word Gap.”  This phrase derives from a longitudinal study of 42 families by Hart and Risley from the University of Kansas on language acquisition and socioeconomic status (SES).  

Study Design

For the first 3 years of the children’s lives, each month they recorded 1 hour of every word spoken between parent and child.  They then painstakingly transcribed and coded the audio recordings. (This was long before computerized language coding and analysis.)  They also tested the children’s language acquisition when they were 3 years old.  In a follow-up study, when the children were between 9-10 years old, they tested the children’s language skills again (29 children).  If you are interested in the details, the results were published in a book, Meaningful Differences in the Everyday Experience of Young American Children (Betty Hart and Todd R. Risley (1995) Paul Brookes Publishing, Baltimore). 

By counting every word spoken to the child in the 1-hour monthly samples and projecting over a 14-hour waking day, they estimated that, by age 3, children in the lowest SES group heard 30 million fewer words than the children in the highest SES group.  Though all the children learned to speak adequately by age 3, the study found that the rate of language acquisition was faster in the highest SES.  Stanford-Binet IQ scores at three years of age correlated with the amount of talking in the home.  

The amount of talk between parent and child was remarkably consistent over the first 3 years.

We saw that these differences between families in amount of talk were so persistently characteristic of ongoing family life that they added up to massive differences in the children’s cumulative experience with language . . . . The amount a parent talked to a child during the first 8 months of observation was strongly associated with the amount the parent talked to the child at 3 years of age (r = .84). – Hart and Risley, p. 70

Based on these findings, there are currently large interventions aimed at increasing the number of words spoken in low income families.

Beyond Word Count, Parenting Matters

The findings discussed above are the most often-cited aspects of Hart’s and Risley’s exhaustive work.  However, there are equally important and powerful findings from their work that are rarely discussed.  Beyond word count, Hart and Risley found that parenting quality matters. They coded the audio to capture five elements of verbal interaction that they combined into an index they called parenting.  The five components of the parenting index were: language diversity, feedback tone, symbolic emphasis, guidance style and responsiveness.  Those of you familiar with the Keys to Interactive Parenting Scale (KIPS) will see much overlap with the 12 KIPS items.

At 3 years of age, the parenting index was a strong predictor of children’s’ IQ, rate of vocabulary growth and vocabulary use.  At 9-10 years of age, parenting quality continued as a strong predictor of receptive vocabulary (r = 0.78) and language skills (r = 0.78), and showed double the predictive strength of SES alone.  These are remarkable predictive values, showing that parenting behavior made a great difference in children’s language skill development.

Parenting Quality Outlasts Impact of SES on Children’s Language

The link between the parents’ income, education, and social status and their children’s academic test performance had declined by third grade. However, the link between what the parents were doing with their children before their children were 3 years old remained as strong as ever over the intervening six years (p < 0.001). -Hart and Risley p. 162

It is surprising that the finding regarding word count has been so widely touted, when the authors themselves say:

We conclude that these [five parenting] variables are not simply marker variables … but powerful aspects of parenting that cause important outcomes in children.  -Hart and Risley, p. 251

Many studies show that the impact of early interventions decline over time. However, this study and many others show the powerful impact of parenting persists long beyond early childhood.  The power of parenting theme continues to grow, from the pioneering longitudinal work of Emmy Werner in Hawaii, to the NICHD longitudinal early child care study, and the recent work of Nobel Prize Winner James Heckman. The evidence continues to mount for the quality of parenting as a predominant factor in children’s learning, development, and well being. Yet, few programs working with families with young children assess parent-child interaction.  I am puzzled by this.  Assessing parenting can guide interventions aimed at helping parents be the best parents they can be, which can launch their children’s lifelong health, development and well-being.