Many of the critics were honestly concerned about the limitations of the formulas and some of them offered alternatives such as usability testing. Although the alternatives are useful and even necessary, they fail to do what the formulas do: provide an objective prediction of text difficulty.

Although the concerns of the formula critics have been amply addressed elsewhere (Chall 1984, Benson 1984-1985, Fry 1989b, Dale and Chall 1995, Klare 2000), we will examine them again in some detail, with a special regard for the needs of technical communication.

The purpose of this article is to very briefly review the landmark studies on readability and the controversy regarding the formulas. I will be happy if you learn something of the background of the formulas, what they are good for, and what they are not. That knowledge will give you greater confidence and method in tailoring your text for a specific audience.

What is readability?

Readability is what makes some texts easier to read than others. It is often confused with legibility, which concerns typeface and layout.

George Klare (1963) defines readability as "the ease of understanding or comprehension due to the style of writing." This definition focuses on writing style as separate from issues such as content, coherence, and organization. In a similar manner, Gretchen Hargis and her colleagues at IBM (1998) state that readability, the "ease of reading words and sentences," is an attribute of clarity.

The creator of the SM"the degree to which a given class of people find certain reading matter compelling and comprehensible." This definition stresses the interaction between the text and a class of readers of known characteristics such as reading skill, prior knowledge, and motivation.

Edgar Dale and Jeanne Chall's (1949) definition may be the most comprehensive: "The sum total (including all the interactions) of all those elements within a given piece of printed material that affect the success a group of readers have with it. The success is the extent to which they understand it, read it at an optimal speed, and find it interesting."

Content

Beginning early in the last century in the U.S., studies of the reading ability of adults and the readability of texts developed in tandem. Our subject matter falls under these headings:

The Adult Literacy Studies These studies discovered great differences in the reading skills of adults in the U.S. and their implications for society.

The Classic Readability Studies This section looks at the early readability studies, which started in the late 19^th century and concluded in the 1940s, with the publication of the popular Flesch and Dale-Chall formulas. During this period, publishers, educators, and teachers were concerned with finding practical methods to match texts to the skills of readers, both students and adults.

The New Readability Studies Beginning in the 1950s, new developments transformed the study of readability, including a new test of reading comprehension and the contributions of linguistics and cognitive psychology. Researchers explored how the reader's interest, motivation, and prior knowledge affect readability. These studies in turn stimulated the creation of new and more accurate formulas.