Table 3.

Cognitive-workload metrics overview.

Cognitive Workload Metrics	Definition
Baselined pupil diameter	The average pupil dilation from baseline time was subtracted from the pupil diameter.
Baselined pupil-diameter derivative	The average pupil-diameter derivative from baseline time was subtracted from the pupil-diameter derivative, and this metric can quantify the extent of pupil dilation or constriction from baseline time.
Baselined standard deviation of the RR intervals (baselined SDNN)	The average SDNN from baseline time was subtracted from the standard deviation of the RR intervals (SDNN).
Baselined Root Mean Square of successive differences between normal heartbeats (baselined RMSSD)	The average RMSSD from baseline time was subtracted from the Root Mean Square of successive differences between normal heartbeats (RMSSD).
Baselined proportion of the number of pairs of successive NN intervals that differ by more than 50 ms divided by the total number of NN intervals (baselined PNN50)	The average PNN50 from baseline time was subtracted from the proportion of the number of pairs of successive NN intervals that differ by more than 50 ms divided by the total number of NN intervals (PNN50).
The low-frequency band (LF)	The low-frequency band is from 0.04 to 0.15 Hz.
The high-frequency band (HF)	The high-frequency band is from 0.15 to 0.4 Hz.
The normalized low-frequency band power (LFnu)	The normalized low-frequency band power is from 0.04 to 0.15 Hz.
The normalized high-frequency band power (HFnu)	The normalized high-frequency band power is from 0.15 to 0.4 Hz.
The ratio of low-frequency to high-frequency (LF/HF ratio)	The ratio of low-frequency to high-frequency is LH/HF.