Task Load Index

Developed by Hart and Stevland (1988), the NASA TLX (Task Load Index) is a multidimensional rating mechanism that evidences a universal Workload score that is based on a weighted average of ratings across six dimensions: Mental Demand, Physical Demand, Temporal Demand, Performance, Effort, and Frustration Level.

NASA-TLX originally consisted of two parts: the total workload is divided into six subjective subscales that are represented on a single page, serving as one part of the questionnaire:

• Mental Demand

• Physical Demand

• Temporal Demand

• Performance

• Effort

• Frustration

There is a description for each of these subscales that the subject should read before rating. They are rated for each task within a 100-points range with 5-point steps. These ratings are then combined to the task load index.