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GOMS Model (Card, Moran, and Newell)

Summary: The GOMS Model is a human information processing model that predicts what skilled users will do in seemingly unpredictable situations.

Originators and proponents: Card, Moran and Newell in 1983; Bonnie John et al.

Keywords: Goals, operators, methods, selection rules

GOMS Model (Card, Moran, and Newell)

This model is the general term for a family of human information processing techniques that attempt to model and predict user behavior. Typically used by software designers, a person’s behavior is analyzed in terms of four components:

• Goals – something that the person wants to accomplish. Can be high level (e.g. WRITE-PAPER) to low level (e.g. DELETE CHARACTER)
• Operators – basic perceptual, cognitive, or motor actions used to accomplish goals, or actions that the software allows user to make (e.g. PRESS-ENTER-KEY or CLICK-MOUSE)
• Methods – procedures (sequences) of subgoals and operators that can accomplish a goal
• Selection rules – personal rules users follow in deciding what method to use in a circumstance

One of the most validated methods in Human Computer Interaction (HCI), the GOMS model assumes expert user and well-defined tasks. It should be noted that there are various limitations to this technique, e.g.:

1. Task in question must be usefully analyzed in terms of the procedural (how to do it) knowledge.
2. Represents only skilled behavior. Not useful for ill-defined problem solving, exploration, etc. Cognitive walkthrough is useful for exploratory behavior by novices.
3. Need to start with a list of top-level tasks or user goals. List must be provided outside of GOMS.

GOMS is useful for uncovering a frequent goal supported by a very inefficient method thereby informing a design change to include a more efficient method.

Variations include:

• Keystroke Level Model (KLM) by Stuart Card: The first, simplest form of GOMS consisting of the sum of subtasks and required overhead. That is, the sum of the time of P – pointing, H – homing, D – drawing, M – mental operator, R – waiting for system response.
• Card Moran Newell (CMN)-GOMS: A serial stage model of GOMS.
• Critical Path Method (also known as Cognitive Perceptual Motor or CPM-GOMS): A parallel stage model (for users with highest level of skill) critical-path-method or cognitive-perceptual-motor analysis of activity – perceptual, cognitive, motor operators can be performed in parallel as the task demands.

For more information, see:

• Card, S., Moran, T., and Newell, A. (1983) The Psychology of Human-Computer Interaction, Lawrence Erlbaum Associates, Hillsdale, NJ. [Book that introduces the GOMS model]
• John, B. and Kieras, D. E. (1996). Using GOMS for user interface design and evaluation: Which technique? ACM Transactions on Computer-Human Interaction (3) 4: 287-319. [Paper explains which GOMS variant to use depending on situation]
• John, B. and Kieras, D. E., (1996). The GOMS Family of User Interface Analysis Techniques: Comparison and Contrast, ACM Transactions on Computer-Human Interaction. (3) 4: 320-351.

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