Textbook of Usability

Cogulator is a free, web-based cognitive modelling tool developed by the US Census Bureau that automates GOMS analysis. Users specify a task as a sequence of operators and Cogulator computes the task time, generates a CPM-GOMS schedule with critical path, and estimates working memory load.

The tool dramatically reduces the effort required for predictive modelling. Where a traditional CPM-GOMS analysis might take hours or days, a Cogulator model can be built in minutes. This makes predictive modelling accessible to practitioners without extensive training in cognitive theory.

Cogulator supports:

• Standard KLM operators (K, P, B, H, M)
• Working memory tracking — which chunks are held at each step
• CPM-GOMS parallel scheduling
• Comparison of multiple designs side-by-side

A related tool, CogTool, was developed at Carnegie Mellon and provides similar capabilities with a storyboard-based interface. Both tools lower the barrier to quantitative usability prediction.

Cogulator is most useful for comparing design alternatives early in the design process, before prototypes exist. It supplements but does not replace user testing — models predict expert performance on specified tasks, not the novice confusion, learning difficulty, or satisfaction that only real users reveal.