Measuring mental workload with the NASA-TLX needs to examine each dimension rather than relying on the global score: an example with driving

Abstract

The distinction between several components of mental workload is often made in the ergonomics literature. However, measurements used are often established from a global score, notably with several questionnaires that originally reflect several dimensions. The present study tested the effect of driving situation complexity, experience and subjective levels of tension and alertness on each dimension of the NASA-TLX questionnaire of workload, in order to highlight the potential influence of intrinsic, extraneous and germane load factors. The results showed that, in complex situation, mental, temporal and physical demand (load dimensions) increased, and that novice drivers presented high physical demand when subjective tension was low on performance. Moreover, increase of mental and physical demand increased effort. It thus, appears essential to distinguish the different components of mental workload used in the NASA-TLX questionnaire. Practitioner Summary: Currently, global score of NASA-TLX questionnaire is used to measure mental workload. Here, we considered independently each dimension of NASA-TLX, and results showed that mental load factors (driving situation complexity, experience, subjective tension and alertness) had a different effect on dimensions, questioning global score use to evaluate workload.

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“…However, it can also be argued that the NASA TLX as an overall value is not sufficiently suitable to distinguish between underutilisation and overstrain. Galy et al [27] have found similar results in a study and therefore suggest to consider the dimensions of the NASA TLX individually. This shows that the NASA score in solo driving is mainly caused by a high effort of the test persons, which differs significantly from the other test rides, although objectively the physical as well as mental effort is lowest.…”

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“…Studies have suggested that a 4-item NASA-TLX may be more suitable for measuring nurse workload, however there is still controversy regarding the application of 4-item or 6-item versions of NASA-TLX in the clinical setting (Galy et al, 2018;Charles et al, 2019). Our current study utilized the 6-item version of NASA-TLX in order to assess different aspects of nurse workload.…”

“…Recent studies showed that factors such as an increased workload, interruptions, level of personal experience, and stress have the ability to in uence mental workload, which can subsequently have an impact on nurses' critical decision making and patients' safety (Happell et al, 2013). However, ergonomics studies have suggested that the measurement of mental workload using the NASA-TLX requires taking into account each of its individual dimensions, rather than simply assessing of the global score (Galy et al, 2018).…”

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