ABSTRACT
This chapter focuses on a program of research directed towards understanding human-computer interaction. It investigates modification model for the WYLBUR editor and showed, in a case study comparing text-editing and typewriting, that it could be used to predict tradeoffs between the two and could also be used in sensitivity analysis. The chapter argues that research should emphasize the development of performance models, enabling designers to predict the performance consequences of design alternatives. Computer text-editing is a prototypical human-computer interaction task, and as such its study is likely to shed light on other human-computer interaction tasks. The Keystroke-Level Model was shown to predict execution time, with an RMS error of 21% for text-editors, graphics programs, and various system utilities. Since new knowledge and insight are often achieved by first focusing on concrete cases and then generalizing, it is necessary to select a task for detailed study, and the task we have selected is computer text-editing.
