Cognitive Dimensions

April 3, 2009

Thomas Green and Alan Blackwell’s 76-page Cognitive Dimensions tutorial made great sleepy train reading.

  1. A system that makes change difficult has a high viscosity. It could happen because a system forces repetition to make changes or because any change entails several other changes to maintain consistency.
  2. Hidden dependencies make it hard to predict the effects of a change.
  3. A system that forces premature commitment is frustrating and scary to use. Would you like to order item #31 from the catalogue? Can’t tell you what it is until you confirm your order…
  4. Abstractions make a system harder to learn (until you learn them) but give it more power. Abstraction-hungry systems require users to create new abstractions before becoming usable.
  5. Systems that permit secondary notation like comments in page margins allow users to escape the formalisms of the environment.  
  6. Visible information is easy to find. A system that permits juxtaposition allows a user to easily compare information side-by-side.
  7. Some systems have a close mapping to their domains.
  8. Consistent systems are easier to use.
  9. Diffuseness is a measure of the terseness of the system’s language and symbols.
  10. Error-prone systems make it easy to make mistakes.
  11. Systems with hard mental operations force the user to think hard.
  12. Progressive evaluation allows a user to check their work at any time.
  13. Provisionality is a measure of how hard it is to change notation already laid down. Pens require more commitment than a pencil mark.
  14. If it is easy to infer a component’s purpose, we say it has good role-expressiveness.

Go forth and design good things!

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One Response to “Cognitive Dimensions”


  1. Aw yeah, Cognitive Dimensions! I first read their work a few years ago, and was pretty into it for a while (c.f. my blog posts: http://tinyurl.com/dyy9qr). It’s still something which I wish would be more widely known than it is — I think it’s a really useful concept.


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