There have been various attempts to modify the NASA-TLX. To account for that intended flexibility, Hart imposed a weighting scheme to ensure the dimensions most critical to each user are emphasized.
Originally, Hart assumed that some combination of these perspectives is likely to represent “most people” and “most scenarios” (Hart, 2006). Noticeably, there are multiple perspectives from which a user may interpret the word “workload”. Performance- How successful do you think you were in accomplishing the goals of the task set by the experimenter (or yourself)? What is your level of satisfaction?.Effort- How hard did you have to work (mentally and physically) to accomplish your level of performance?.Frustration- How insecure, discouraged, irritated, stressed, and annoyed versus secure, gratified, content, relaxed and complacent did you feel during the task?.Temporal- How much time pressure did you feel due to the rate or pace at which the tasks or task elements occurred? Was the pace slow and leisurely or rapid and frantic?.Physical- How much physical activity was required? Was the task easy or demanding? Slow or brisk? Slack or strenuous? Restful or laborious?.Mental- How much mental and perceptual activity was required? Was the task easy or demanding, simple or complex, exacting or forgiving?.Meaning, there are six sub-scales that eventually comprise one overall NASA-TLX score (Hart & Staveland, 1988): The NASA-TLX is a multi-dimensional scale. Researchers simply cannot get the information they want through observation. The “immediate, often unverbalized impressions that occur spontaneously” (Hart & Staveland, 1988) are of particular interest, as they are either difficult or impossible to observe objectively. The NASA-TLX estimates one or more users’ perceived cognitive demand, which can help gauge a system’s usability, effectiveness, or comfort. With more than 8,000 citations since 1988, it has spread far beyond its original application of aviation, focus, and the English language (Hart, 2006). Staveland of San Jose State University introduced the Task Load Index. Hart of NASA’s Human Performance Group and Lowell E. Reading Time: 4 minutes NASA TLX for Human Factors Research
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