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on measures of reading level

From: Matt May <mcmay@bestkungfu.com>
Date: Thu, 3 May 2001 23:39:00 -0700
Message-ID: <045501c0d464$f6328ce0$6601a8c0@sttln1.wa.home.com>
To: <w3c-wai-gl@w3.org>
I've done some research on reading level algorithms, and I think what I've
found is enough to give us pause with respect to putting any real faith in
the numbers that are produced, or basing any guidelines on them.

The first one I researched was the Flesch-Kincaid grade level. The algorithm
is as follows:
(.39 * w) + (11.8 * s) - 15.59
w is the average number of words per sentence, and
s is the average number of syllables per word.
Negative FK results are reported as zero. Numbers over 12 are reported as

FK is based on the Flesch Reading Ease score, which is itself just a measure
of syllable count and sentence length. The modified algorithm was published
in 1975 by a researcher trying to create readable documents for enlisted
personnel in the US Navy, and doesn't appear to have any real attachment to
education, much less cognitive disability. The subjects in Kincaid's
research were adults, presumably skewed 18-30 and male (and by definition
skewed American), and the resulting algorithm really wasn't intended to be
utilized as widely as it is.

The other major grade-level index is the Gunning Fog index. Its algorithm
(w + h) * .4
w is the average number of words per sentence, and
h is the percentage of words with three or more syllables ("hard words")

Gunning Fog is capped at 17, where "17-plus" is suggested as
postgraduate-level writing.

Both of these algorithms reward short, monosyllabic sentences, irrespective
of how many of these sentences are necessary to communicate the point. These
indices are also not meant to rate an entire document, but rather
extrapolate scores from small passages (100 words).

I picked a couple of random examples to illustrate results. The first
sentence of Lincoln's Gettysburg address rates a 12 (the raw number is
closer to 18) on FK, while Gwendolyn Brooks' poem "We Real Cool"[1] rates a
0. I was a third-grader when I studied Lincoln, not a post-doctorate, and I
think I still got the gist. :)

Now, here's the part that bugs me. First off, by interjecting sentences like
this previous one (short, no polysyllabics), I can lower the overall score
of this message. And if the goal of a site is to work its way down to a
prescribed reading level, then that is likely to be what they try to do:
they'll boil down the content by working it until it comes up with a low
enough score, and say that's that. No real usability or accessibility gain
can be found by fostering this type of practice, where people are writing to
the index, rather than to the reader.

Secondly, syllable count is a really weak measure of complexity. Is
"Germany" a more difficult message to communicate than "France"? Do
7-year-olds know what a brad is? The idea is based on an assumption that
longer words are harder than short ones. There's a correlation there, but
it's not reliable. Just as relevant to comprehension are educational
environment, cultural influence, and above all, context.

My last problem is that none of these actually check spelling or grammar. It
seems those might be somewhat relevant, as well.

The information that I read seemed to suggest (where it didn't say outright)
that reading-level indices have been used largely as pseudoscience: an
overly simplistic "scientific" numeric answer to the readability of a

I found a document[2] which lines out ten principles of clear statement. I
think this is a lot closer to my ideal of providing content providers with
solid guidance for good writing, and in fact, we may want to consider asking
to incorporate these principles. This document comes from the creators of
the Gunning Fog index, circa 1973, and at the end, it emphasizes that
systems like the fog index, while of some utility, are not a panacea:

"It is important not to over-use the fog index. Use it only occasionally to
spot-check your writing. Don't write to make a good fog index score. That
will make you write short, choppy sentences. Like these.
Instead, learn and practice using the 'Ten Principles of Clear Statement.'
If you observe these guides to good writing, your writing will naturally
grow easier to understand."

[1] http://www.poets.org/poems/poems.cfm?prmID=1233
[2] http://muextension.missouri.edu/xplor/comm/cm0201.htm
Received on Friday, 4 May 2001 02:44:40 UTC

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