NASA Task Load Index (NASA-TLX)
A 6-dimension subjective workload scale completed immediately after a task.
By Claire White
- Self-administered after completing a task; approximately 5 minutes.
- Six subscales: mental demand, physical demand, temporal demand, performance, effort, and frustration.
- Each subscale rated 0 to 100 in 5-point increments.
- Overall workload score is the unweighted mean of all six subscales (Raw TLX) or a weighted mean.
- Reference information. It does not diagnose.
What it measures
The NASA-TLX captures the subjective workload of completing a task. After a task, the person rates six dimensions: how much mental and perceptual activity was required (Mental Demand); how much physical activity was required (Physical Demand); how time-pressured the task felt (Temporal Demand); how successful they were (Performance); how hard they had to work (Effort); and how irritated or stressed they felt (Frustration). In BCI and AAC research it is used to assess the cognitive and emotional burden of operating a communication interface.
What the result tells you
Higher overall scores indicate higher subjective workload. The NASA-TLX is used to compare versions of an interface, input methods, or protocols — lower scores indicate a less burdensome design. The Raw TLX (unweighted mean of all six subscales) is commonly used in BCI research as it performs comparably to the weighted version with less administration burden.
Evidence, psychometrics and provenance
Psychometrics
- Test-retest reliability
- Moderate to high across task types
- Construct validity
- Correlates with objective workload measures across many domains
References
- 1.Hart SG, Staveland LE. Development of NASA-TLX: results of empirical and theoretical research. In: Hancock PA, Meshkati N, eds. Human Mental Workload. Amsterdam: North-Holland; 1988:139-183.