As far as I understand, readability formulas use calculations based on the number of sentences, words, syllables and characters and also on the frequency of words which aim to determine the reading level of a certain text and, therefore, to predict the difficulty readers will have to understand it. I have some serious reservations towards such approach to reading.
First of all, it assumes that the reading process can be reduced, to a certain extent, to a mathematical equation. As an academic discussion, this is as old as the hills. Anyone involved with research social in sciences knows how much ink has been spilled in discussing whether, or not, social phenomena can be objectively, precisely and systematically represented and explained by measurable data. As I see it, reading is a social phenomenon. I believe the discussion goes beyond what ‘works’ – it’s a matter of ontological and epistemological understanding of the act of reading. Personally, I do not believe in an approach to reading that sees it as a fundamentally empirical, objective, generalizable and replicable process. People who believe it is so, would probably be able to manipulate these formulas to make them ‘work’.
Second, readability formulas focus exclusively on the text as an artifact. Manipulating the variables in the production of this artifact you should be able to make it more or less readable. It may take neurosciences into consideration; however, it does not seem to me that it takes the social construction of texts on board. What a reader makes of a text, the difficulties and the pleasure – to go back to Rob’s point – a reader extracts from a text depend on the each person’s previous reading experiences, social, historical and cultural backgrounds. To assume that one formula can cater for the immense variety of readers’ responses is to believe that one size fits all.
Last but not least, it assumes that reading is simply a decoding process. Once you break the code, you understand the text. I believe reading is much more than decoding and even more than interpreting. For me, the act of reading is as an act of meaning creation. Reading is a matter of interaction between the individual, as a social being, and the text, as a socially, historically and culturally laden creation.