Hierarchical task analysis (HTA)
A method that starts from a task's goal and divides it into ever more concrete subgoals and operations, along with the plans that say when and in what order each one is done.
What it’s for
It helps you understand in detail how a complex task is done, to design the interface, training or procedure without missing steps.
Key elements
Start from the goal
Describe what is to be achieved, not just the list of movements.
Plans, not just steps
Each level says in what order things are done, under what conditions, or which happen at the same time.
Stop where it makes sense
Keep dividing as long as failing at that point is likely or costly.
How it’s done
Set the main goal of the task.
Divide it into subgoals and operations, with the plans that order them.
Mark the weak points where an error would be likely or serious.
Applications in design
When to use it
When a task has many steps, decisions or risks, as in industrial or medical systems or long administrative processes.
Avoid
Describing only how it should be done; observe how people actually do it.
Don’t fall for it
Review it with the people who do the task every day before designing from it.
Connections
Authors and works
- 1967
J. Annett and K. D. Duncan
They proposed analyzing tasks as a hierarchy of goals to design operator training, and stopping the analysis when the risk of error no longer justifies more detail.
Sources
Original sources
- Annett, J., & Duncan, K. D. (1967). Task analysis and training design. Occupational Psychology, 41, 211–221.
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