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NASA Task Load indeX (TLX)

NASA Task Load indeX is used to measure workload from all aspects, including mental workload, physical workload, etc. Users can give rating for the several measures, indicating their reactions toward the given tasks.

Here is an except from NASA Ames Research Center’s instructions of implementing NASA TLX.

Title Endpoints Descriptions
MENTAL DEMAND Low/High How much mental and perceptual activity was required (e.g., thinking, deciding, calculating, remembering, looking, searching, etc.)?  Was the task easy or demanding, simple or complex, exacting or forgiving?


Low/High How much physical activity was required (e.g., pushing, pulling, turning, controlling, activating, etc.)?  Was the task easy or demanding, slow or brisk, slack or strenuous, restful or laborious?


Low/High 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?
EFFORT Low/High How hard did you have to work (mentally and physically) to accomplish your level of performance?
PERFORMANCE Good/Poor How successful do you think you were in accomplishing the goals of the task set by the experimenter (or yourself)?  How satisfied were you with your performance in accomplishing these goals?


Low/High How insecure, discouraged, irritated, stressed and annoyed versus secure, gratified, content, relaxed and complacent did you feel during the task?

One question remain not so explored: what is the relations between each measure? For different types of tasks, are the measures of equal importance? If not, how do we decide the importance? For cases where we only need the TLX as a reference, this question is not so vital. But if we want to determine what constitute the most to the workload, we need to, maybe, firstly decide the relative importance of each measures.

For reference, this is a sample TLX questionnaire.


About Xiang 'Anthony' Chen

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