Summary of my notes from the books The design of everyday things by Donald A. Norman and How to solve it by George Polya.


There are three models:

  • Design Model, The conceptualization the designer had.
  • User Model, What the user develops to explain the operations of the system.
  • System Image, The physical appearance.

The aim is to align the user model and the design model. A user’s model is formed via the system model and preconceived ideas about how the system should function so it is important that the system image convey a clear picture of the design model and that the design model is simple to conceptualize.

Making things simple to Conceptualize

  • Simplify the structure of the task, minimize the amount of planning or problem solving required.
  • Make things visible,:
    • Allow people to know what is possible.
    • Allow people to understand what the effect of an action will be.
  • Get the mappings right, so that users can determine:
    • between intention and possible action.
    • action and their effect on the system.
    • actual state and perceived by sight state.
  • Exploit the power of constraints.
    • Make the user feel like there is only one thing to do.
    • Plan for error
  • When all else fails standardize, it is only useful if everybody knows it and adheres to it.

Action cycle

  • Form the goal ( I need more light to read ).
  • Form the intention ( Open the blinds or turn on the light ).
  • Specify the actions needed to achieve the intention ( Plan if needed ).
  • Execute the actions.
  • Perceive the state of the world.
  • Interpret the state of the world.
  • Evaluate the outcome.

Problem solving

  • Understand the problem
  • Create a plan of action
  • Execute the plan
  • Evaluate the outcome


  • For this to be useful it is kind of important that you have a good understanding of what is simple in regard to human cognition.