Comparing Estimates of Vocabulary Acquisition

Many estimates of vocabulary size exist, with variability being their one constant.  The difficulties inherent in measuring vocabulary size have not stopped multiple researchers from coming up with their own numbers, some of which I’ve summarized below.


Despite the almost inevitable variation, the studies that support these estimates have told us some important things, such as…

  • School age language acquisition occurs primarily through incidental experience more than formal teaching.
  • Word learning shifts from concrete and functional to abstract and unusual.  This shift occurs gradually from third grade through the high school years.
  • Environment matters.  Extreme environments extremely matter. 

There are many more of these studies than even what I’ve listed, and while I’m not saying I’ve seen it happen, it is possible that people could cherry pick ones that most support the point trying to be made.  Also, there is no consensus among anyone really, of what exactly counts for a word in these studies.  Does examine, examines, examined, etc. count as different words or variations of the same word?  Ultimately the numbers themselves aren’t as important as are examining what’s possible and what’s actually occurring.  We know from these studies that it is possible to learn many, many words – at rates of up to 14 words a day according to at least two sources.  Methods of teaching vocabulary – such as teaching categories, word webs, and using reading to facilitate vocabulary acquisition – can be helpful, but ultimately nothing works like an enriched experience.

Keep reading for more information about the sources of these studies.

Anglin (1993) from Wagovich and Newhoff; The Single Exposure:  Partial Word Growth Through Reading; The American Journal of Speech Language Pathology, November 2004.

 Beck and McKeown (1991) from Beck, I.L. and McKeown, M.G. (1991). Social studies texts are hard to understand: Mediating some of the difficulties. Language Arts, 68, 482-490. from

 Goulden, Nation, and Read (1990) from this link:

 Lipsett/ Mehrabian and Owens numbers are from Language Development  – An Introduction; Robert E. Owens, Jr.; Allyn and Bacon; 1996

 Hart and Risely (1995) taken from American Educator, Spring 2003, excerpt from their 1995 book, Meaningful Differences in the Everyday Experiences of Young American Children; Brookes Publishing

 Miller and Gildea (1997) from Later Language Development; Marilyn A. Nippold; Pro-Ed; 1998