On the Failure of Readability Formulas to Define Readable Texts: A Case Study from Adaptations

IN THE PAST 30 OR 40 YEARS there has been much discussion of objective formulas to measure the readability of texts. These formulas measure variables such as sentence length and familiarity of vocabulary, but do not define the actual features of texts which make them easy or hard to read. In this study, we compared two versions of four texts, the original versions intended mainly for adult readers, and the adapted versions intended for less skilled readers. We discuss the specific changes made to make the texts easier to read, with their apparent motivations. Some changes, such as splitting complex sentences into component clauses, changing vocabulary items, etc., may have been made to make the text conform to a certain level of readability defined by formulas. But these changes are not always the most successful, and some actually make the text harder to understand. Other changes could not have been made solely because of the effect they would have on readability measurement. They were influenced by factors such as definition of discourse topic, logical ordering of ideas, background knowledge assumed in the reader, and choices of syntactic structure which do not affect length. Adaptations were found to be most successful when the adaptor functioned as a conscientious writer rather than someone trying to make a text fit a level of readability defined by a formula. We argue strongly against the implicit use of readability formulas as guides to writing graded texts and urge experimental research to define the real factors constituting readability.