Human Factors and Behavioral Science: A Study of the Match Between the Stylistic Difficulty of Technical Documents and the Reading Skills of Technical Personnel

How well technical documents communicate with their readers depends in part on the style in which they are written, since the way ideas are expressed can influence how easily they are understood. Readers may find a document particularly difficult to read when its writing style places an undue burden on their reading skill. For example, use of words that are unfamiliar to readers can obscure a document's message. Also, a document can be unclear if ideas are embedded in sentences whose syntax is too complex for its readers. Other characteristics of style are described elsewhere in this issue of the Journal.1 The stylistic difficulty of written communication can be appraised with the help of readability formulas.2,3 These formulas predict the reading difficulty that may result from a document's writing style but not from its content, organization, or format. Readability formulas estimate the reading skill needed to cope with a document's writing style, as manifested in the writer's choice of surface structures. A readability index is calculated from measures of text features that are thought to be indicators of stylistic difficulty. For example, many formulas use the average length of a text's words and sentences to calculate readability. These two text measures, word length and sentence length, function primarily as indicators of the lexical and syntactic difficulty of the text. In English, shorter words are likely to be more familiar to readers than longer words, since shorter words tend to occur more frequently.