GOMS (Wikipedia)
An encyclopedia article on GOMS (Goals, Operators, Methods, and Selection rules): a family of models, introduced by Stuart Card, Thomas Moran, and Allen Newell in their 1983 book The Psychology of Human-Computer Interaction, for predicting how long a skilled user will take to perform a procedure on an interface without running a live usability test. Wikipedia articles are continuously edited, so year above reflects the access date (2026-07-16), not a fixed publication year.
License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/
Key points
- Four components: Goals (a state to be achieved, described without saying how), Operators (elementary perceptual/motor/cognitive acts), Methods (operator sequences that accomplish a goal), and Selection rules (which Method to use when more than one exists for the same goal).
- The Keystroke-Level Model (KLM), the simplest variant, sums per-operator average execution times across six operators — K (keystroke), P (pointing), H (homing), D (drawing), M (mental preparation), R (system response) — as Texecute = TK + TP + TH + TD + TM + TR.
- A modern Touch Level Model (TLM, Rice and Lartigue) adapts KLM to touchscreens with Tap, Swipe (~70ms), Zoom, Pinch, and Gesture operators.
- CMN-GOMS is the original, fuller model (subgoals and real selection rules, for tasks with more than one valid method); NGOMSL is a structured natural-language notation that additionally predicts learning time, not just execution time, by expanding goals hierarchically top-down.
- CPM-GOMS (Bonnie John and David Kieras) models cognitive, perceptual, and motor processors running in parallel rather than one operator at a time, closer to genuinely skilled, overlapping behavior.
- Project Ernestine (New England Telephone): a CPM-GOMS analysis predicted a new workstation design would cause a 3% productivity decrease; the actual measured decrease was 4% — and the analysis correctly located the cause as underused slack time in operators’ existing routines, not the keystroke-count reduction the redesign had been built around.
- Richard Gong’s CAD-software redesign case used GOMS to flag inefficient methods for frequently-performed goals, missing methods for common goals, and inconsistency across similar goals.
- Limitations: only models skilled/expert use (not novices, error rates, mental workload, fatigue, or learning time — except NGOMSL’s learning-time prediction); treats all users as identical; addresses usability only, not whether the right feature/task was chosen; needs accurate baseline operator-time data to be reliable. Recent extensions adapt it to model users with disabilities.
- Modeling tools exist (QGOMS, CogTool, Cogulator) for building and running GOMS analyses without hand calculation.