How many words do you need to know ?

Research indicates that if the students know about 98% of the words on a page, then they can read it quickly and with high levels of comprehension. Below 90% (one unknown word in 10) the reading becomes frustrating and slow requiring a lot of dictionary use and comprehension suffers badly.
The Extensive Reading Foundation’s Guide to Extensive Reading

I first came across this research while teaching English 109, and it sure corresponds to my experience. 

If my students knew just 90% of the words in a text, they couldn’t read it at all, even with the definitions of new vocabulary words typed in the margins. 

I’m sure the problem is working memory.

Every time you look up a new word you have to remember a) what you were just reading, b) the ‘name’ of the new word, and c) the new word’s definition.

Plus you have to moosh all these things together into a meaningful whole, an operation that is also performed by working memory.

And since you know only 90% of the words, you have to do this over and over again, which erodes your memory of the other words you just looked up, not to mention your memory (and, consequently, your understanding) of the essay as a whole. 

It’s like trying to multiply 79 by 6 inside your head. You have to remember the 79, you have to remember the 6, you have to remember the subproducts (is that the right word ? I don’t remember !), and you have to perform the calculation. 

It’s too much.

This is why schools should teach vocabulary.

13 thoughts on “How many words do you need to know ?

    1. 79*6 is even easy mental math if you do it the long way: 9*6 = 54, and 70*6=420, and 420+54=474. I do this all the time while I’m walking or shopping.
      For example, on this morning’s walk back from the gym*, I calculated how many miles per week I’ve averaged biking this year, based on last night’s total from the bike share website, plus an approximation of the distance of my two short rides this morning to and from the gym, divided by the number of weeks so far this year, which I got by adding up the number of days in each month plus 10 for May and dividing the sum by 7.
      My mental math went like this: Last night’s total was 326.5, and this morning’s rides totaled about 3.5, so that’s about 330 total miles. January and March have 31, so that’s 62, and April has 30, so that’s 92, and February has 28, so that’s 120 days, plus 10 for May is 130 days. So 330 miles in 130 days. To get miles per week, I want 330/130 miles/day * 7 days/week, but it’s easier to do (33*7)/13. 33*7 is 21*11, which is 231. 13*10 is 130, and 231-130 is 101. 13*7 is 91 (a memorized fact), so there are 10 left over, and 10/13 is close to 3/4. So my final answer is 10 + 7 + about 3/4, or about 17 and 3/4 miles per week. … At which point, I still had another four blocks to walk.
      When I’m trapped and can’t move, like in an MRI or the dentist’s chair, I close my eyes and work on squares of two-digit numbers. But maybe I’m weird.
      *If this doesn’t make sense, from the gym I ride a dockable bike-share bike back to the closest dock, which is 3/4 mile from my house, and then walk the 3/4 mile home. So I get an upper-body workout at the gym, a short bike ride, and a medium walk.


  1. This makes me think of our friend John McWhorter, who has argued that Shakespeare needs to be updated for modern readers/viewers.

    Citing observations that “about 10% of the words that Shakespeare uses are incomprehensible in modern English,” McWhorter notes: “When every 10th word makes no sense—it’s no accident that the word decimate started as meaning “to reduce by a 10th” and later came to mean “to destroy”—a playgoer’s experience is vastly diluted.”

    He has a point!

    Liked by 1 person

  2. The argument for keeping Shakespeare “pristine*” is the same as the argument for resuscitating dying languages: there’s something somehow special about the actual words used that communicating the same message in different words would not replicate. I don’t find it compelling in either case.

    * To the extent that bawdy Elizabethan plays can be thought of as “pristine”. 😎

    Liked by 1 person

    1. Efforts to preserve old language help to slow the otherwise very rapid change of language. Overall, this helps with communication and with understanding of history. In the case of Shakespeare, much of the poetry is lost in attempts to modernize the language, because modern poetic conventions are rather different from Elizabethan ones.

      What tends to happen in productions is that dramaturges help actors understand the meaning of the lines, and the actors then use their acting skills to convey the meaning to the audience. Some of the jokes are lost (puns lost because of changes in pronunciation, bawdy jokes lost because of forgotten euphemisms), but much of the content can still be conveyed. Cultural references that would be completely lost on modern audiences are often cut from the plays in performance.

      Watching a good performance is a more rewarding experience than reading Shakespeare, in part because of this assistance in understanding provided by a well-trained and well-educated cast.

      Liked by 1 person

      1. <>


        Ed took a Shakespeare course his first semester in college & listened to all the plays on tape. He says that’s the only way he would have understood them.


  3. Here’s an example of a “revolutionary 10% translation” of Shakespeare cited by McWhorter:

    (Macbeth pondering his plan to kill King Duncan)

    The original:

    Besides, this Duncan
    Hath borne his faculties so meek, hath been
    So clear in his great office, that his virtues
    Will plead like angels, trumpet-tongued, against
    The deep damnation of his taking-off.

    The update:

    Besides, this Duncan
    Hath borne authority so meek, hath been
    So pure in his great office, that his virtues
    Will plead like angels, trumpet-tongued, against
    The deep damnation of his knocking-off.

    Liked by 1 person

  4. Spot on, as usual.

    Catherine – you wouldn’t believe how many times I quote nuggets of wisdom I have learned from you over the years.

    Sent from Outlook



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