What Does Cognitive Psychology Tell Us about Users?

Information Processing Principles | Applying the Principles

Information Processing Principles

Cognitive psychology derived a number of principles regarding how humans process information. These principles, though quite general, give good advice for making software easier to use.

  • As a rule of thumb, the working memory span is about 7 ± 2 items.
  • Human processing capacity is limited and has to be divided between tasks.
  • High frequency repetition of tasks can lead to "automatic" execution, thus increasing the capacity for other tasks. However, automation requires hundreds to thousands of learning trials (performance follows a power function in time).
  • Recognition is easier than remembering (recall).
  • Elaboration of information leads to better memory.
  • Good organization of information (chunking, clustering, categorizing) leads to better remembering.
  • Keeping the context for learning and recall (e.g. software use) constant leads to better remembering.
  • Pictures plus text are remembered best. Pictures alone are remembered better than text alone.
  • Pictures are extremely well recognized.
  • Reaction time increases (logarithmically) in relation to the number of alternatives.
  • Users create mental models of their software when they are working with it. These models are simplistic (incomplete), informal, often concrete, and may contain errors. Mental models help users to envision, predict, and explain system actions. They aid users in planning their actions.
  • Metaphors may help users to transfer their prior knowledge to a new software.

 

Applying the Principles

In the following, we present some applications of the principles listed above. As you will see, these general principles are very useful heuristics.

Principle Application
Working memory span is 7 ± 2 Do not ask users to remember more than 5 to 7 items.
Example: Do not ask users to remember long lists of items or commands.
Extension: Do not ask users to remember anything that the system already knows.
Limited human processing capacity If users have to struggle with their software, there is no capacity left for their task.
Example: Do not include animated GIF images in a Web page, as these images distract users.
Example: Do not require users to remember anything while engaged in another challenging task.
Automation of tasks You can expect "automatic" execution only for tasks that are repeated over and over.
Example: Do not expect casual users to become proficient with your software. Instead, make it simple to use!
Recognition vs. remembering Provide choices in the form of menus or lists instead of requiring the users to key in a choice.
Example: Provide help on input values (F4 help in R/3).
Extension: Functions on pushbuttons in the R/3 application toolbar are easier to find than functions that are located somewhere in the menu tree only, because users need not remember their position in the menu tree.
Elaboration of information

 

 Superficial engagement in a software will not lead to an understanding of its working. Therefore motivate users to use your software!
Extension: Do not frustrate users. Frustrated users will no longer be engaged in your application and its requirements.
Organization of information Try to organize information, functions, and screen elements in sensible units.
Example: Order lists alphabetically, by date, or any other scheme that makes sense in the application context.
Example: Cluster fields into sensible groups.
Constant context for learning and recall Create a stable working environment for your users.
Example: Reserve a permanent area for navigation buttons.
Remembering of text and pictures Try to use pictures, or pictures with text, where possible.
Example: Present regions of a country as a map.
Recognizing pictures Familiar icons may provide clues to the functioning of your software, even for casual users.
Example: Use familiar navigation buttons.
Number of alternatives Try to limit the number of alternatives for menu choices, function selections, and so on.
Example: Instead of letting users scan the menu tree, provide pushbuttons with the relevant functions.
Mental models Help users to create simple, effective mental models of your application. Provide clues that lead to such models in an intuitive way.
Example: Provide clues about the structure of your application or about the sequence of steps in a procedure.
Example: Provide clues about how users should navigate in your application.
Metaphors If the task at hand is suited, use real world metaphors to organize your software.
Example: You can use a room metaphor for your Web application: Each room corresponds to a certain type of processing. Organize the rooms and the transitions between them in a way that makes sense to users.
Example: You can use a book metaphor for a Website that provides information.

 

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Source:  Simplifying for Usability