An SR Research EyeLink 1000 eye-tracker sampling at 1000 Hz was
used to ensure correct fixation during the entire stimulus presentation.
A nine-point automatic calibration was used with participants'
dominant eye (as determined by the Miles test) before every block. If
participants lingered over 10 s without triggering the fixation-trigger,
a drift-correction was engaged. After two drift-corrections, a midblock
recalibration was performed. Participants used a chin rest to aid
in maintaining a constant head-position.