Understanding Lexiles

Often when trying to discuss the development of reading proficiency, measurement specialists and reading specialists seem to be talking at cross-purposes. There may be more to the issue than either perspective recognizes. Reverting to argument by metaphor, measurement specialists are talking about measuring weight; reading specialists, about providing proper nutrition.

There is a great deal involved in physical development that is not captured when we measure a child's weight and the process of measuring weight tells us nothing about whether the result is good, bad, normal, try to schedule a doctor's appointment, or go to the emergency room without changing your clothes. Evaluation of the result is an analysis that comes after the measurement and depends on the result being a measure. No one would suggest that, because it doesn't define nutrition, weight is not worth measuring or that it is politically sensitive to talk about in front of nutritionists. A high number does not imply good nutrition nor does a low number imply poor nutrition. However, a measurement of weight is always a part of any assessment of well-being.

A Lexile score [based on sentence length and word frequency in the general language], applied to people, is a measure of reading ability, which is taken to mean the capability to make meaning from words and sentences. Lexiles, as applied to text, is a measure of how difficult it is to make meaning from that text. A colleague of mine offered as a counter example Hemingway's "For Whom the Bell tolls" (840L). Since a 50 percentile sixth grade reader could self engage with this book, something must be wrong because the book was written for adults. This counter-example of an instance where Lexiles "do not work", if true, is an interesting case. I have two counter-arguments: one, all measuring instruments have limitations to their use and, two, Lexiles may actually be describing Hemingway appropriately.

First, outside the context of Lexiles, there is always difficulty in scoring exceptional, highly creative writing for both humans and computer algorithms. (I would venture to guess that many publishers, who make their livings recognizing good writing, would reject Hemingway, Joyce, or Faulkner-like manuscripts if they received them from unknown authors.) I don't think it follows that we should avoid trying to evaluate exceptional writing. But we do need to know the limits of our instruments.

I rely, on a daily basis, on a bathroom scale. I rely on it even though I believe I shouldn't use it on the moon, under water, or for elephants. It does not undermine the validity of Lexiles in general to discover an extraordinary case for which it does not apply, if that is in fact the case. Again, we need to know the limits of our instrument.

Second, given that we have defined the Lexile for a text as the difficulty of decoding the words and sentences, the Lexile analyzer may be doing exactly what it should with a Hemingway text. Decoding the words and sentences in Hemingway is not that hard: the vocabulary is relatively simple, the sentences relatively short. The Lexile score will reflect that.

Understanding and appreciating Hemingway is something else again. I am trying to make a distinction between reading ability and reading comprehension. You have to be able to read before you can comprehend what you have read. Analogously, you have to be able to do arithmetic before you can solve math word problems. The latter requires the former but the former does not guarantee the latter.

The Lexile metric is a true developmental scale that is not related to instructional methods or materials, or to gradelevel content standards. The metric reflects increasing ability to read, in the narrow sense, increasingly complex text. As students advance through our reading/language arts curriculum, they should progress up the Lexile scale. Effective standards-based instruction should cause them to progress on the Lexile scale; analogously good nutrition should cause children to progress on the weight scale.

One could coach children to progress on the weight scale in ways counter to good nutrition. One might subvert Lexile measurements by coaching students to write like Hemingway, on one end, or like Supreme Court Justice Antonin Scalia, on the other. There need to be other checks to ensure that we are effecting what we set out to effect. This does not invalidate either weight or reading ability as useful things to measure.

There are many things in the curriculum that are not assessed directly by the Lexile analyzer. Understanding imagery and literary devices, locating topic sentences and main ideas, recognizing sarcasm or satire, comparing authors' purposes in two passages would not be considered in the Lexile measure. The role of standardsbased assessment is to identify which constituents of reading ability and reading comprehension are present or absent.

The role of the Lexile measure is to provide a measure of the student's status on a narrowly defined, interval scale that extends over the length of reading from Dick and Jane to Scalia and Roberts. It does not define reading, recognize the breadth of the ELA curriculum, or replace grade-level content standards-based assessment, but it can help us understand the results of the assessment and help us design instruction appropriate to the student. On the one hand, we cannot expect students to say anything intelligent about text they cannot decode, nor should we attempt to assess their analytic skills using that text. On the other hand, we should expect to assess and improve their analytical skills using text they can decode.

Ronald Mead
Data Recognition Corp.


Understanding Lexiles. Ronald Mead … Rasch Measurement Transactions, 2007, 21:2 p. 1100

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