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FAQ: How can I analyze data within a specific time window (setting interest periods)?
#1
Different time frames can be defined by creating Interest Periods within the Data Viewer viewing session. Once a given Interest Period is set, the data shown and reports generated will be limited to only those samples and events that occur during that particular time window. To define an Interest Period, click the dropdown arrow in the Interest Period Manager and select the  "Edit..." option.

   

In the Interest Period Manager window, click the “New Interest Period” button to create new Interest Periods or manage existing ones.

   

When defining an Interest Period in the Interest Period Editor, there are various ways to define the start and end of each period. The most common approach to defining the start of an Interest Period is to use messages that were written to the EDF file by the  stimulus presentation software to mark the onset of critical trial events. INPUT (TTL based) events can also be used.  The end of an Interest period can also be defined using messages, but a simple duration or INPUT / BUTTON event can also be used. More details on how to define Interest Periods can be found in the Data Viewer Manual (Help menu -> Contents -> Data Analysis and Output -> Interest Periods).

   

There are also a few preferences to be aware of when dealing with Interest Periods. All of the following can be found in the Preferences tab of the Inspector window -> Data Filters.
  • Show Interest Areas Pre/Post Interest Period: If checked, Interest Areas that exist on displays before and after the currently-selected Interest Period will be displayed. If unchecked, these Interest Areas will not be displayed.

  • Hide Spanned Events at Start/End of IP: Hide gaze events (fixations, saccades, and blinks) that start before the beginning of the currently-selected Interest Period and end after the beginning of the currently-selected Interest Period and hide gaze events that start before the end of the currently-selected Interest Period and end after the end of the currently-selected Interest Period. This will hide them from the various views of Data Viewer and will exclude them completely from Reports and Fixation Maps.

  • Trim Spanned Fixation Duration at Start/End of IP: Trim the duration of fixations that start before the beginning of the currently-selected Interest Period and end after the beginning of the currently-selected Interest Period and trim the duration of fixations that start before the end of the currently-selected Interest Period and end after the end of the currently-selected Interest Period. Trimming them will effectively exclude the portion of the spanned fixation that falls outside the Interest Period. This will influence the spanned fixations' duration in the various views of Data Viewer and in the output that goes into Reports and Fixation Maps.
Please see the Interest Periods section under Data Analysis and Output in the Data Viewer User Manual (Help menu -> Contents) for more information on creating and using Interest Periods.