Template: Gaze Boundary Crossing
Gaze Boundary Crossing

Required Experiment Builder Version: 1.4.128 or higher
EyeLink Required: Yes
Type: Complete Example
Difficulty Level: Moderate

This example illustrates:
  • How to use the Invisible Boundary trigger to detect a change in participant's gaze
  • How to perform online timing performance analysis

Each trial of this experiment requires two versions of image files being prepared in advance (one normal sentence and one sentence with the target word replaced with a priming non-word; please take a look at the example images provided in the "\library\images" folder of the project).

The project also provides examples for the calculation of several time delays:
  • time_sample_display: the overall delay between the triggering sample and display change (start of the retrace that the screen was actually drawn / redrawn);
  • time_sample_boundary: the delay between the occurrence of the sample and the trigger firing;
  • time_boundary_display: the delay between the Invisible Boundary trigger and the display change.
Please note that in theory the time delay between the occurrence of one eye sample and the display change based on that eye sample depends on a couple of factors, such as the time to get the eye event / sample, noise filtering, graphics drawing preparation, and screen updating. The actual delay may also be influenced by how you run your experiment (real-time, deployed version, other programming running, computer specifications, etc...; you may check out Experiment Builder Checklist Item #14. Have you taken measures to maximize real-time performance of the display PC when running the experiment?).

Some of the project settings that are relevant to boundary manipulations / performance:
  1. Display refresh rate (DISPLAY Device -> Refresh Rate) is set to 120 Hz (a higher refresh rate is recommended).
  2. The link filter (EYELINK Device -> Link Filter Level) is set to normal. Users may turn this filter off to reduce link delay (but expects noisier link data).
  3. The project location type ("Edit -> Preferences -> Screen -> Location Type") is set to TopLeft Position. The "boundary" column specifies the triggering x boundary position. You may set the boundary location to an intended location depending on your theory / research interest; In this example, the boundary location was to the last letter of the word before the target word.
  1. Download the Boundary_Final.ebz example from this message.
  2. Launch the Experiment Builder application.
  3. Unpack the Boundary_Final.ebz file to a location on your Experiment Builder PC with "File -> Unpack".
  4. Open the project in Experiment Builder.
  5. Deploy the project to a new folder.
  6. Run the Boundary_Final.exe from the deployed directory.

.ebz   Boundary_Final.ebz (Size: 69.89 KB / Downloads: 67)