2.4.1. Eye blink rate
As spontaneous EBR remains steady during the day but increases in the evening (at about 20:30, see Barbato et al., 2000), no EBR was recorded after 18:00. Participants were also urged not to smoke before their arrival. Throughout the experiment, the spontaneous EBR was measured three times for each participant. At the start of each Ocular task, a nine-point eye-movement calibration was performed, which was followed by a light gray screen with a central fixation cross for 3 min. Participants were sat comfortably alone in the room and asked not to gaze, but just to look casually at the fixation cross in a relaxed state. The individual EBR (blinks/min) was calculated by dividing the total number of eye blinks during the 3 min measurement interval by the duration (in minutes). Eye blinks were marked by the Eyelink online event parser using a proprietary algorithm based on several consecutive missing pupil samples, which was independently demonstrated to identify blinks accurately (Ehinger et al., 2019). The blinks that were outside of the normal range of blink duration were removed to assure data quality in blink measurements (less than 80 ms or more than 900 ms, as reported by Ehinger et al., 2019).