FAQ: What messages do I need to send to Data Viewer if I'm not using Experiment Builder?
There are several types of integration messages that should be sent by your stimulus presentation software so that Data Viewer can parse and display your data correctly. The key types of message are outlined below, please see EyeLink Data Viewer Integration Messaging Protocol or the Data Viewer User Manual for more details (Help menu -> Contents -> Protocol for EyeLink Data to Viewer Integration).
  1. Messages identifying the Start and End of each trial: These allow Data Viewer to parse the data into separate trials. By default Data Viewer expects a TRIALID message to define the start of a trial and a TRIAL_RESULT message to define the end of a trial. 
    • TRIALID message should be in the following format: TRIALID 1 in which the number after the TRIALID specifies the current trial number.
    • TRIAL_RESULT message should be in the following format: TRIAL_RESULT 0, no trial number is needed for this message.
    If other messages and / or TTL input are used to specify the start and / or end of a trial, change the Data Viewer preference prior to importing EDF files so that Data Viewer can correctly parse the trials. To do, set the Trial Segmentation Type, the Trial Load Start Value, and the Trial Load End Value (Preference Tab of the Inspector window -> Data Loading).


  2. Messages telling Data Viewer which images to display: . IMGLOAD messages should be sent immediately after any changes in the stimulus display are made. These messages will ensures that Data Viewer can display the new stimulus at the correct time(note this is not the same as messages used to set up Interest Periods and code other relevant information).
    • IMGLOAD messages should be in the following format:

      !V IMGLOAD CENTER <image_path_relative_to_the_edf> <x_position> <y_position> [width] [height].

      E.g. !V IMGLOAD CENTER fixations.gif 200 200 100 100. If the width and height are not specified the image will be displayed at the original size.
  3. Messages coding the values of Trial Variables:. Variables such as condition / block / accuracy etc can be used by Data Viewer to group trials. Messages that code the values of each variable should be sent at the end of each trial, right before the TRIAL_RESULT message. Trial variables will be available as columns that can be included in reports and use to group trials in Data Viewer.
    • Trial Variable messages should be in the following format:

      !V TRIAL_VAR <trial_var_label> <trial_var_value>

      E.g. !V TRIAL_VAR condition gap
  4. Messages defining Interest Areas:  There are three main types of Interest Areas: rectangle, ellipse, and freehand.
    • Rectangle Interest Areas should be in the following format:

      !V IAREA RECTANGLE <id> <left> <top> <right> <bottom> [label string]

    • Ellipse Interest Areas should be in the following format:

      !V IAREA ELLIPSE <id> <left> <top> <right> <bottom> [label string]

    • Freehand Interest Areas should be in the following format:

      !V IAREA RECTANGLE <id> <x1, y1> <x2, y2 > ... <xn, yn> [label string]

      where x and y coordinates are points of the Freehand Interest Area.
It is very important to send "standard" messages throughout the trial - to signal key trial events such as changes to the stimulus display, keyboard or button responses etc. Ideally a message should be written to the EDF every time the stimulus changes during the experiment, or any input is received. These messages can be used to set Interest Periods in Data Viewer, and limit analyses to critical time windows (eg when a specific stimulus was on screen).