The Design of Everyday Things

The devices will be able to do many useful things, but I fear they will also frustrate: so many things to control, so little space for controls or signifiers. The obvious solution is to use exotic gestures or spoken commands, but how will we learn, and then remember, them?

To summarize: • Affordances are the possible interactions between people and the environment. Some affordances are perceivable, others are not. • Perceived affordances often act as signifiers, but they can be ambiguous. • Signifiers signal things, in particular what actions are possible and how they should be done. Signifiers must be perceivable, e

It is the conceptual model that provides true understanding. So I now turn to these fundamental principles, starting with affordances, signifiers, mappings, and feedback, then moving to conceptual models.

Goal (form the goal) 2. Plan (the action) 3. Specify (an action sequence) 4. Perform (the action sequence) 5. Perceive (the state of the world) 6. Interpret (the perception) 7. Compare (the outcome with the goal)

But as soon as there is a problem or a misunderstanding, the problems arise.

There we have it. Seven stages of action: one for goals, three for execution, and three for evaluation (Figure 2.2). 1. Goal (form the goal) 2. Plan (the action) 3. Specify (an action sequence) 4. Perform (the action sequence) 5. Perceive (the state of the world) 6. Interpret (the perception) 7. Compare (the outcome with the goal) The seven-stage a

The signifier is an important communication device to the recipient, whether or not communication was intended.

An affordance is a relationship between the properties of an object and the capabilities of the agent that determine just how the object could possibly be used.

Getting the specification of the thing to be defined is one of the most difficult parts of the design, so much so that the HCD principle is to avoid specifying the problem as long as possible but instead to iterate upon repeated approximations.