When I wrote the post on readability and promised a follow-up, I had no idea I was wading into an argument that has apparently waged for almost a century. William H. Dubay gives an exhaustive overview of the various formulas, theories, supporters, and detractors of readability in a 2004 tract entitled “Principles of Readability”. This oft-cited document is a great starting place for further research into readability formulas and its development.

The basic argument comes down to what a formula can and cannot measure. Many formulas use some combination of word counts, sentence length, difficult or simple word counts (using compiled word lists), word length, syllable count, number of different words, number of indeterminate clauses, comprehension tests, counts of parts of speech (pronouns, prepositions, etc.), and number of prepositional phrases, to name a few. There are other elements of a piece of reading that have been more resistant to being quantified in a way that can be distilled into a formula. Examples are prior knowledge, motivation, organization, style, coherence, and density of ideas. Some argue that elements inherent to the reader, such as motivation, prior knowledge, and purpose, need to be taken into account when measuring readability. But what all this means is that there are some things that readability formulas are good for and some things they are not good for.

The shortest word is not always the simplest, the most ‘familiar’ word is not always the best; the shortest sentence is not always the clearest or the most readable.

1. Teachers do have to choose books based on difficulty and taking their students skills into account. So some measure of readability is needed. Some research suggests that the more familiar a teacher is with the material, the more likely they are to overestimate the readability of the text, sometimes by as much as eight academic years (Kasule, 2011). Therefore a rating of readability could help attenuate these overestimations and improve a teacher’s choice of best-fit books.
2. Readability formulas are quite good at judging the relative readability between texts. Even if a particular formula may poorly judge which book is perfect for which student, it will generally tell which book will be easier or harder for that student to read (Klare & Buck, 1954).
3. These formulas are easy to administer, often performed by the publisher in advance. Therefore they are a convenient reference for the time-strapped teacher (Janan & Wray, 2012).

1. Some readability formulas are only text based, ignoring the other aspects of a book that make it comprehensible to a reader, such as the pictures and images and the context in which the reader has begun to read. As Klare and Buck (1954) point out, “the shortest word is not always the simplest, the most ‘familiar’ word is not always the best; the shortest sentence is not always the clearest or the most readable.”
2. The difficulty of a text is compounded by gaps in linguistic and cultural knowledge. This reduces the effectiveness of a readability formula even further in the case of language learners and linguistically diverse classrooms (Kasule, 2011).
3. Many of the formulas produce results in ‘Years of Education’ or ‘Grade Level’ needed to read a text independently. As any classroom teacher knows, the grade of a child does not always represent the reading level.

While readability formulas have a place in our modern educational institutions, they have significant limitations. However, to abandon them completely because of their shortcomings would leave nothing to take their place. Teachers should continue to use these convenient ratings but supplement that information with what they know about their student. For example, a student that grew up in a densely populated city may have no contextual foundation for understanding a story about what we can find in the garden. Likewise, a student with low motivation may struggle with a book that is at their `level` simply because they do not have the will to try and comprehend words that aren’t immediately recognizable.

Readability formulas will continue to have their supporters and detractors but, as usual, teachers will continue to use what helps their kids the most. Whether that is the Flesch Reading Ease formula or the five-finger rule, the goal is to get the best book in the hands of ready readers.

Dubay, W. H. The Principles of Readability, Costa Mesa, CA: Impact Information, 2004.

Janan, D., and Wray, D., Readability : The limitations of an approach through formulae, Br. Educ. Res. Assoc. Annu. Conf. Univ. Manchester, pp. 1–16, 2012.

Kasule, Daniel. “Textbook readability and ESL learners.” Reading & Writing [Online], 2.1, 63-76, 2011.

Klare, George R., and Byron Buck. Know Your Reader: the Scientific Approach to Readability. Hermitage House, 1954.

One comment

  1. […] However, while reading I was impressed by the vocabulary of the book and had a sense that it was a little too advanced for independent reading in Grade 3. This led me to use various tools online to determine the reading and grade level of the book. What I found intrigued me. There are many useful tools out there for analyzing text. I will talk about a few of them here and discuss the efficacy of such tests and benchmarks in a later post. […]

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