Chapter 1 The Psychopathology of Everyday Things of Design of Everyday Things has provided me some very great insights on principles of physical design. Author Norman has illustrated his ideas with many real life good and bad examples like telephones, cars, and watches which I can closely relate in my everyday life. I understand that how we work/use/operate things should be reflected by the design of the things themselves without any needs for words or symbols.One of the most important principles of design is visibility. Natural design gives natural visual cues to convey how to correctly work with things. A successful design should have visible instruction or cues with feedback of actions, and there should be enough feedback for different features. There should also be a close relationship between what you want to do and what seems possible when mapping things. Natural mapping between a control and its function comes from physical analogies and cultural standards, rather than arbitrary decisions. There should also be constraints to limit the possibilities to avoid confusion. The psychology of materials/affordance of things(purpose) also matters: different materials is used for different things, which also direct people to interact with things differently.
A designer's job is to fit how things work into the psychology of people. A conceptual model should make effective use of affordance, constraints and mapping and allow users to form clear user model/mental model through interacting/experiencing with the system model. Interface wise, if the number of possible actions exceeds the number of control, things can become difficult, because controls with more than one action are harder to remember and use, and when the number of controls equals that of functions, each control can be specialized. Sometimes designers are unwilling to let go of some features, resulting in an over complicated interfaces that were meant for very simple purposes. To get the right product out it is normal for designers to take many attempts and trials and errors.
The development of technology follows a U shaped curve, starting with high surprise, dropping to low, comfortable level and rise again. As industry stabilize, new features and capabilities are added at the cost of decreased simplicity and reliability. "The same technology that simplifies life by providing more functions in each device also complicates life by making the device harder to learn, harder to use. This is the paradox of technology." With clever design, complexity and difficulty can be avoided when functions are added.
Norman further emphasized in Chapter 1, “Attractive Things Work Better” of Emotional Design that beauty is as important as function and usability .
"Affect also has a major impact on how well we are able to perform tasks. Negative affect focuses the mind, leading to better concentration. In cases of an immediate threat this is good, for it concentrates processing power upon the danger. When creative problem solving is required this is bad, for it leads to narrow, tunnel vision. Positive affect broadens the thought processes, making it more easily distractible. When the problem requires focus, this is bad, but when the problem is best addressed through creative, out-of-the-box thinking, then this is precisely what is needed. Affect therefore regulates how we solve problems and perform tasks. Negative affect can make it harder to do even easy tasks: positive affect can make it easier to do difficult tasks. "
"Now consider the implications of these findings upon design. A short summary is that good human-centered design practices are most essential for tasks or situations that are stressful: distractions, bottlenecks, and irritations need to be minimized. In pleasant, positive situations, people are much more likely to be tolerant of minor difficulties and irrelevancies. In other words, although poor design is never excusable, when people are in a relaxed situation, the pleasant, pleasurable aspects of the design will make them more tolerant of difficulties and problems in the interface."