The Hart-Risley 30 Million Word Gap Study – 1995

After decades of collaborating to increase child language vocabulary, Betty Hart and Todd Risley spent two and a half years intensely observing the language of 42 families throughout Kansas City.  Specifically, they looked at household language use in three different settings:  1) professional families; 2) working class; and 3) welfare families.  Hart and Risley gathered an enormous amount of data during the study and subsequent longitudinal follow-ups to come up with an often cited 30 million word gap between the vocabularies of welfare and professional families by age three.  This controversially large number came from the data that showed welfare children heard, on average, 616 words per hour, while children from professional families (essentially children with college educated parents) heard 2153 words per hour.  The longitudinal research in the following years demonstrated a high correlation between vocabulary size at age three and language test scores at ages nine and ten in areas of vocabulary, listening, syntax, and reading comprehension.  This study was subsequently used to fuel the fire of arguments for early childhood programs such as Head Start.

For an excellent summary of this study, read this.  A good comment on this study and poverty’s influence on education can be found here.

13 thoughts on “The Hart-Risley 30 Million Word Gap Study – 1995

    1. There is definitely a lot of info on that site, with a lot of impressive names in education in learning. I’m looking forward to exploring it some more.


  1. I think there is a lot of misunderstanding about their findings. We simply do not know how important repetition and breadth of vocabulary is to cognitive development. We don’t know that more is always better, there may be a threshold at which ‘normal’ brain and cognitive development occurs, and maybe the less talkative poor people more than meet that threshold. In simple statistical terms, the numbers this study cites (a ’30 million word gap’) is misleading because in the largest estimation THERE ARE ONLY 1 MILLION WORDS IN THE ENGLISH LANGUAGE, there are only 171,000 words in the massive Oxford English Dictionary, and most people only use 5-10,000 words in their active and passive (reading) vocabularies. A more accurate statistic is this (with still a stark contrast): “Apparently, pre-schoolers of professional families are typically exposed to 2,150 different words, pre-schoolers from working class families to 1,250 words, while those from households on welfare just 620.” Flynn, James R. (2008). Where Have All the Liberals Gone?: Race, Class, and Ideals in America. Cambridge University Press


  2. It seems this study is being interpreted differently. Does a child from academic family hear 2,150 words per hour, as the initial post states, or do they possess a 2,150 vocabulary? If so, how is “knowing vocabulary” assessed?
    2,150 words per hour equals 350 words per minute or close to six words per second. Unlikely even for intellectuals to accomplish that.
    So, if the number is for vocabulary, what age are we talking about? Three year olds?

    @ Chris P
    >>We simply do not know how important repetition and breadth of vocabulary is to cognitive development.<<
    This is not true. We do know that the brain needs repetition to create automaticity for words, and it is obvious that breadth of vocabulary has a direct relation to cognitive development. It's its foundation!


  3. This is inequality. Then how does a poor family on welfare help their children to achieve higher levels in their vocabulary? Who then educates their parents? Where does this transition begin? Many poor families are illiterate. Where does the help come from especially in poor communities?


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