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.