A Theory of Usability Based on a Model of Discourse Processing

Abstract

Industry’s efforts to develop routine and systematic usability testing programs for documentation have been hampered because professional communication has yet to develop a coherent theory of usability. Recent criticisms of usability research design assumptions and test management methods are symptoms of this condition. In a review of twenty-two experimental usability studies published in books and journals between 1980 and 1989, Mire1 (1991) concludes that the failure of investigators to effectively base their usability research designs on the findings of earlier investigations has resulted in a lack of coherence among studies. This situation limits what can be said confidently concerning our understanding of usability in hard copy documentation. She also criticizes investigators for failing to use more heterogeneous groups of test subjects, a design weakness that limits our ability to generalize across populations of users. A second study has examined some of the factors that constrain usability testing in the work environments of three high-technology companies. (Skelton 1992) Testing in these fis is not a routine measure of product quality. It tends to be done on an ad hoc basis by writers and editors who, in most instances, also develop the tested document. The tests are usually administered late in the product development cycle and are often conducted only once. The numbers of communicators experienced in usability testing is relatively small for each company. In general, testing is limited significantly by budget and staff constraints, even though all the respondents in the study who had participated in usability testing programs agreed that testing should become a routine part of product development. Although two of the companies had started training communicators to do their own testing, some of the respondents resisted this idea, citing the demands of their present duties as the reason. Its value not yet determined, usability testing has received a tentative endorsement at best from the three businesses in this study. What we have, then, is a Catch-22. It appears that the managers and communicators in the study summarized above remain reluctant to commit more financial, professional, and personal resources to expand what is now essentially a trial-and-error process that can complicate as well as enhance product development. Yet, the expansion of in-house resources for usability testing development is essential if testing is to receive a fair hearing in the corporate board room. How would a theory of usability change this situation? It would have to support decisions concerning the way we allocate and use testing resources. The theory would need to identify what happens when readers interact with text. It would have to describe the principal components of comprehension and explain how they function in order to support decisions concerning test design, administration, and interpretation. The van Dijk-Kintsch strategic model of discourse comprehension (1983) is a step toward such a theory. Unless otherwise stated through citations, most of the material in the following discussion of the model has been derived from Strategies of Discourse Comprehension, by van Dijk and Kintsch.