Assessing Mental Workload with Subjective Measures: An Analytical Review of the NASA-TLX Index Since its Inception

Abstract

The use of subjective ratings to measure mental workload is a commonly used technique. Several measures have been designed to test such workload metrics specifically in the aviation community. One such measure is the NASA Task Load Index (NASA-TLX). The NASA-TLX is a multidimensional measure of workload based on the weighted averages of six sub-scales. These include mental demand, physical demand, temporal demand, performance, effort and frustration. The current study sought to examine the aviation human factors literature for the various methods and reporting techniques used to report the results from the administration of the NASA-TLX. Results indicated the workload measure is used in numerous contexts and there exists great variability in reporting techniques. The authors discuss these issues as well as make declarations as to the advantages of standardizing the reporting methods when the NASA-TLX measure is employed.