09-03-2020, 08:02 AM
Spanned Events occur when the Interest Period boundary falls in the middle of a gaze Event (i.e. a fixation or saccade). For instance, a Spanned Fixation is any fixation that either starts before or ends after an Interest Period boundary. See an example of a Spanned Fixation below.
Data Viewer allows these Spanned Fixations to be treated in a number of ways. They can be hidden (in which case they will be excluded from any output report and will not contribute to any variables such as IA_DWELL_TIME), or they can be trimmed (in which they will be included in Reports, but their fixation will be trimmed to the duration of the fixation included within the Interest Period, and only that duration will contribute to variables such as IA_DWELL_TIME). By default, Spanned Fixations are trimmed, but not hidden. Data Viewer allows fixations that span the start or end of the Interest Period to be treated separately.
To alter the way in which Data Viewer deals with Spanned Fixations, first make sure you have set an Interest Period. The click on the Preferences tab of the Inspector window and select Data Filters in the list of Preferences. Hiding or trimming Spanned Fixations at the start and end of the selected Interest Period can be controlled via the preferences highlighted below.
To exclude the first fixation in each trial select the “Hide Spanned Events at Start of IP”.
Data Viewer allows these Spanned Fixations to be treated in a number of ways. They can be hidden (in which case they will be excluded from any output report and will not contribute to any variables such as IA_DWELL_TIME), or they can be trimmed (in which they will be included in Reports, but their fixation will be trimmed to the duration of the fixation included within the Interest Period, and only that duration will contribute to variables such as IA_DWELL_TIME). By default, Spanned Fixations are trimmed, but not hidden. Data Viewer allows fixations that span the start or end of the Interest Period to be treated separately.
To alter the way in which Data Viewer deals with Spanned Fixations, first make sure you have set an Interest Period. The click on the Preferences tab of the Inspector window and select Data Filters in the list of Preferences. Hiding or trimming Spanned Fixations at the start and end of the selected Interest Period can be controlled via the preferences highlighted below.
- Hide Spanned Events at Start of IP -- If checked this will exclude fixations, saccades, and blinks which span the start of the Interest Period from all Data Viewer reports.
- Hide Spanned Events at End of IP -- If checked this will exclude fixations, saccades, and blinks which span the end of the Interest Period from all Data Viewer reports.
- Trim Spanned Fixation Duration at Start of IP -- If checked this will trim the duration of a fixation that spans the start of the Interest Period to the duration that is within the Interest Period. For example, if a fixation starts at time 200 and ends at time 500 and the Interest Period starts at time 300, then the fixation duration will be reported as 200 msec if this option is checked and 300 msec if this option is unchecked.
- Trim Spanned Fixation Duration at End of IP -- If checked this will trim the duration of a fixation that spans the end of the Interest Period to the duration that is within the Interest Period. For example, if a fixation starts at time 200 and ends at time 500 and the Interest Period ends at time 300, then the fixation duration will be reported as 100 msec if this option is checked and 300 msec if this option is unchecked.
To exclude the first fixation in each trial select the “Hide Spanned Events at Start of IP”.