Norman Doors

Norman Doors





Unnatural Mapping

Natural Mapping

Conceptual Models

“A conceptual model is an explanation, usually highly simplified, of how something works. It doesn’t have to be complete or even accurate as long as it is useful."

There is no good conceptual model for understanding the operation of my watch. It has five buttons with no hints as to what each one does. And yes, the buttons do different things in their different modes. But it is a very nice-looking watch,

The lack of immediate feedback for the actions did not help: it took 24 hours to see whether the new setting was appropriate. I shouldn’t have to keep a laboratory notebook and do controlled experiments just to set the temperature of my refrigerator.

If the system lets you make the error, it is badly designed. And if the system induces you to make the error, then it is really badly designed.

A thermostat with an explicit conceptual model

A thermostat with an explicit conceptual model


“Constraints are powerful clues, limiting the set of possible actions. The thoughtful use of constraints in design lets people readily determine the proper course of action, even in a novel situation.”





A designed constraint: a forcing function

Taking constraints too far

Convention as a constraint



We must design our machines on the assumption that people will make errors

More and more often the blame is attributed to “human error.”....

"Human error" usually is a result of poor design: it should be called system error. Humans err continually; it is an intrinsic part of our nature. System design should take this into account. 

Pinning the blame on the person may be a comfortable way to proceed, but why was the system ever designed so that a single act by a single person could cause calamity? Worse, blaming the person without fixing the root, underlying cause does not fix the problem: the same error is likely to be repeated by someone else.

My Criticisms

  •     Poor (visual) design(!)
  •     Bad photographs / graphics
  •     Repetitive
  •     Few examples of good design

The problem with the designs of most engineers is that they are too logical. We have to accept human behavior the way it is, not the way we would wish it to be.


By Fergal Walsh


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