The Design of Everyday Things

by Donald A. Norman

Designers need to focus their attention on the cases where things go wrong, not just on when things work as planned. Actually, this is where the most satisfaction can arise: when something goes wrong but the machine highlights the problems, then the person understands the issue, takes the proper actions, and the problem is solved. When this happens smoothly, the collaboration of person and device feels wonderful.

The insights from the seven stages of action lead us to seven fundamental principles of design: 1. Discoverability. It is possible to determine what actions are possible and the current state of the device. 2. Feedback. There is full and continuous information about the results of actions and the current state of the product or service. After an action has been executed, it is easy to determine the new state. 3. Conceptual model. The design projects all the information needed to create a good conceptual model of the system, leading to understanding and a feeling of control. The conceptual model enhances both discoverability and evaluation of results. 4. Affordances. The proper affordances exist to make the desired actions possible. 5. Signifiers. Effective use of signifiers ensures discoverability and that the feedback is well communicated and intelligible. 6. Mappings. The relationship between controls and their actions follows the principles of good mapping, enhanced as much as possible through spatial layout and temporal contiguity. 7. Constraints. Providing physical, logical, semantic, and cultural constraints guides actions and eases interpretation.

Mistakes often arise from ambiguous or unclear information about the current state of a system, the lack of a good conceptual model, and inappropriate procedures. Recall that most mistakes result from erroneous choice of goal or plan or erroneous evaluation and interpretation. All of these come about through poor information provided by the system about the choice of goals and the means to accomplish them (plans), and poor-quality feedback about what has actually happened.

Effective design needs to satisfy a large number of constraints and concerns, including shape and form, cost and efficiency, reliability and effectiveness, understandability and usability, the pleasure of the appearance, the pride of ownership, and the joy of actual use.

In theory, there is no difference between theory and practice. In practice, there is.

I propose a “Law of Product Development”: DON NORMAN’S LAW OF PRODUCT DEVELOPMENT The day a product development process starts, it is behind schedule and above budget.

Designers need to understand their customers, and in many cases, the customer is the person who purchases the product, not the person who actually uses it. It is just as important to study those who do the purchasing as it is to study those who use it.