Table 3.

Examples of metrics modulated by prolonged continuous use that can be used for adaptive system design.

Type		Metric	Effect*	Type of study**	References
Covariate	Time	TOT	↑	Operator monitoring	Rodríguez-Fernández et al. (2017)
		Time of day		Operator monitoring	Sikander and Anwar (2019)
Behavioral	Driving	Steering corrections	↓	Operator monitoring	McDonald et al. (2012), Li et al. (2017)
	Computer	Mouse and keyboard		Characterization	Pimenta et al. (2013)
Physiological	EEG	α and θ band power	↑	Multiple	Borghini et al. (2014), Roy et al. (2014), Jahanpour et al. (2020), Tran et al. (2020)
		Left connectivity	↓	Operator monitoring	Sun et al. (2014)
	fNIRS	Connectivity		Operator monitoring	Dehais et al. (2018)
		Frontal oxygenation	↓	Operator monitoring	Ahn et al. (2016)
	Occular activity	Blink Rate and duration	↓	Review	Borghini et al. (2014)
		Saccade Velocity	↓	Review	Di Stasi et al. (2013)
		Fixation and focus	↓	Characterization	Roy et al. (2016a)
	Cardiac activity	Heart rate	↓	Operator monitoring	Lal and Craig (2001), Ahn et al. (2016)
		Heart rate variability	↑	Multiple	Zhao et al. (2012), Borghini et al. (2014), Melo et al. (2017), Huang et al. (2018)
	Body posture			Operator monitoring	Furogori et al. (2005), Ansari et al. (2021)

Upwards arrows indicate an positive correlation with mental fatigue and vice versa.

^*If no effect is displayed this is either due to the effect not being explicitly reported or due to the effect being to complex for the table;

^**Operator Monitoring includes studies regarding mental fatigue estimation; Characterization refers to studies that experimentally show the effects of mental fatigue, but do not estimate mental fatigue, while Multiple includes combinations of any of the categories.