Problem arise when we cannot "see" how to do use a device

It is possible to determine what actions are possible and the current state of the device

A conceptual model is the mental model that people carry of how something should be done.

The conceptual model enhances
both discoverability and evaluation of results

Mental models are what people really have in their heads and what guides their use of things

The designer designs a conceptual model into the system in
order for it to appear graspable and coherent to the user

Relationship between controls and their movements and the results in the world

Improve spatial arrangement and temporal continuity to maximize effectiveness.

Sending Information back to the user about what has been done

Needs to be immediate and synchronized with user action

After an action has been executed, it is easy to determine the new state.

Using suitable signifiers improves discoverability, communication, and understanding of feedback.

possible interactions between people and the environment

The proper affordances exist to make the desired actions possible

Restricting the possible actions that can be performed

Helps prevent user from selecting incorrect options

An example is the logical relationship between
physical layout of a device and the way it works

Norman states, "Semantic constraints rely upon the meaning of the situation to control the set of possible actions."

Has to deal with the environment that one is to interpret the different workings of a certain design

Norman states, "Cultural issues are at the root of many of the problems we have with new machines: there are as yet no accepted conventions or customs for dealing with them.