Donald A. Norman. The Design of Everyday Things. New York: Doubleday/Currency, 1990.
In Chapter 1, "The Psychopathology of Everyday Things," Norman promotes visibility as "one of the most important principles of design" (4). Designers should adhere to what he calls "natural design." If a door is intended to be pushed, "the designer must provide signals that naturally indicate where to push." Excessive visibility, however, is a detriment to usability, for it interfers with "the mapping between intended actions and actual operations." Norman argues that "just the right things have to be visible; to indicate what parts operate and how...." Modern devices like VCRs, audio sets (and, I might add, computer interfaces) too often are ridden with gadgets and features that intimidate the user because of their excessive visibility. Instead, visibility, appropriate cues, and feedback for users' actions should constitute, according to Norman, the "psychology of everyday things." A designer must understand not only the psychology of human beings but also the psychology of "how things work" (12).
For Norman, good design is predicated on a mapping between the user's mental model and the designer's design or conceptual model.
The user's model is the mental model developed through interaction with the system. The system image results from the physical structure that has been built (including documentation, instructions, and labels). The designer expects the user's model to be identical to the design model. But the designer doesn't talk directly with the user -- all communication takes place through the system image. If the system image does not make the design model clear and consistent, then the user will end up with the wrong mental model. (16)Norman uses a compelling example of the automobile as design where the user's mental model and the designer's conceptual model are optimally mapped. If the car demonstrates good design, it is because "things are visible" and the driver is the happy recipient of "natural relationships" between controls and what is controlled. The driver can understand the car's system where "single controls often have single functions" and "the relationships among the user's intentions, the required actions, and the results are sensible, nonarbitrary, and meaningful" (22).
The bottom line is customer satisfaction rather than customer frustration. If the design of modern telephone systems fares less well than that of the automobile, Norman argues it is because they "have more features and less feedback," thus making them more difficult to learn and use" (27).
Norman presents the book's title as a "lesson in design," a lesson that focuses on understanding user needs and usability testing with actual users. If designers trust only their instincts, they will run the risk of user error, user frustration, and even low user morale.
The contents of The Design of Everyday Things include the following chapters: