Understanding mental fatigue and its detection: a comparative analysis of assessments and tools

Abstract

Mental fatigue has shown to be one of the root causes of decreased productivity and overall cognitive performance, by decreasing an individual's ability to inhibit responses, process information and concentrate. The effects of mental fatigue have led to occupational errors and motorway accidents. Early detection of mental fatigue can prevent the escalation of symptoms that may lead to chronic fatigue syndrome and other disorders. To date, in clinical settings, the assessment of mental fatigue and stress is done through self-reported questionnaires. The validity of these questionnaires is questionable, as they are highly subjective measurement tools and are not immune to response biases. This review examines the wider presence of mental fatigue in the general population and critically compares its various detection techniques (i.e., self-reporting questionnaires, heart rate variability, salivary cortisol levels, electroencephalogram, and saccadic eye movements). The ability of these detection tools to assess inhibition responses (which are sensitive enough to be manifested in a fatigue state) is specifically evaluated for a reliable marker in identifying mentally fatigued individuals. In laboratory settings, antisaccade tasks have been long used to assess inhibitory control and this technique can potentially serve as the most promising assessment tool to objectively detect mental fatigue. However, more studies need to be conducted in the future to validate and correlate this assessment with other existing measures of mental fatigue detection. This review is intended for, but not limited to, mental health professionals, digital health scientists, vision researchers, and behavioral scientists.

Keywords: Attention; Digital health; Executive function; Mental health; Mental load; Saccades.

Figure 1. An example timeline of a trial involving an anti-saccade task.

(A) Participants fixate on a central point. (B) A saccade signal appears in the peripheral visual field simultaneous with the removal of the fixation point. (C) A correct antisaccade is generated in the direction opposite to the signal.

Figure 2. Conventional electrodes placement for eye movement measurement.

Electrode placement for (A) new proposed EOG and (B) conventional forehead EOG. Red circles represent negative electrodes and green circles represent positive electrodes. The Black circle represents the ground electrode. The vertical (V) and horizontal (H) electrodes are used to detect vertical and horizontal saccades, respectively.