An EyeLink 1000 Plus Tutorial: Running an Experiment
©
2013-2017 SR Research Ltd.
85
system presents these targets in a random order, which discourages
participants from anticipating the location of the next target, and saccading
away from the current target before it disappears. However, it is important to
remind the participant to look at each calibration target until the next target
appears.
If automatic sequencing has been enabled, targets will be presented and
fixations collected without further intervention. Each time a new target is
displayed, the participant should quickly make a saccade to it. The EyeLink
1000 Plus system detects these saccades and the fixation following, producing
an automated sequencing system.
NOTE: Sequencing may halt if the improper setup of the eye causes pupil loss
or noise at the target position. If this happens, press the ‘ESC’ key twice to exit
the calibration, adjust the threshold and/or the participant setup, and then
restart the calibration. Pressing the ‘ESC’ once will restart the calibration
whereas pressing it twice will exit calibration and return to the Camera Setup
menu.
Even though the calibration is automatic, watch the Host PC’s display carefully.
Note the position of the cross-shaped pupil position markers: these should form
a grid shape for the 9-point calibration. Lapses of participant attention will be
clearly visible in the movements of this cursor. Also visible will be any
difficulties the participant has in fixating targets, and most camera setup
problems. The following figure illustrates a good calibration (left panel) and a
poor calibration (right panel).
Good Calibration
Poor Calibration
Figure 3-19: Calibration Grid
For some participants (especially those with neurological conditions) short
fixations or lapses of attention can make the automated procedure unusable. A
manual calibration mode can be used for these participants, where the
↵
(ENTER) key or space key must be pressed to collect each fixation. Pressing the
‘M’ key switches automatic calibration off. It may be switched back on by
pressing the ‘A’ key.
