Other Parameters; Sample Configurations - SR Research EyeLink Portable Duo User Manual

Fixation updates are most useful for real-time display paradigms. In some
studies, the participant is required to fixate a target while stimuli are presented.
Fixation updates can be used to check gaze position every 100 ms or so.
Computer interfaces operated via eye movements is a paradigm dramatically
simplified by fixation updates. Actions are triggered by gaze on an active area of
the screen for a critical duration. This is implemented simply by counting
sequential fixation updates that fall within the area.
Two commands set the fixation update interval and data accumulation period
in milliseconds. Usually these are set to the same value. An interval of zero
disables fixation update. An update interval of 50 or 100 ms is a good choice:
fixation_update_interval = 50
fixation_update_accumulate = 50

4.3.8 Other Parameters

The EyeLink PARSER.INI configuration file contains other commands that
configure the parser. These are of several types:
Verification delays. These set the time in milliseconds that the parser
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requires a detector output (saccadic velocity or acceleration thresholds, or
missing pupil for blink) to be stable before the parser changes its state and
sends events to the data file or link. These values have been determined
empirically, and there is little advantage to changing them.
Parser filter types. Two velocity filters are available: fast and slow. The fast
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filter works better in most cases. The slow filter is less noise-sensitive, but
increases saccade duration and decreases sensitivity slightly.
Saccade extension. This is intended to allow the saccade period to include
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the lower-velocity start and end of the saccadic period. This is usually
disabled, as its effect is minor.
Internal constants. These MUST NOT be changed.
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4.3.9 Sample Configurations

The complete set of commands for the most useful tracker configurations is
given below. The cognitive configuration is conservative, is less sensitive to
noise and ignores most saccades smaller than 0.6°. The psychophysical
configuration is useful for neurological and smooth-pursuit research, and
reports very small saccades. It also better estimates saccade durations and
average velocities.
Cognitive Configuration:
recording_parse_type = GAZE
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