During a standard Drift Check procedure, the Host PC software requires manual input from the operator to confirm that the drift is acceptable and the trial can proceed. Having a standard Drift Check prior to each trial is the optimal way to ensure spatial accuracy is maintained during the entire task.
If your task involves many short trials, you may prefer not to have to perform a manual Drift Check prior to each trial. One solution is to skip the manual Drift Check procedure entirely and replace it with an automatic 'Pseudo Drift Check' within the RECORDING sequence. If the automatic drift check passes, the trial continues. If it fails, a standard Drift Check is performed, providing the operator with the opportunity to recalibrate if necessary.
The attached example illustrates one approach to implementing this in Experiment Builder.
Simple_PseudoDriftCheck.ebz (Size: 190.82 KB / Downloads: 85)
How the Pseudo Drift Check Example Works
Here is a step-by-step breakdown of how the attached example project is configured:
If your task involves many short trials, you may prefer not to have to perform a manual Drift Check prior to each trial. One solution is to skip the manual Drift Check procedure entirely and replace it with an automatic 'Pseudo Drift Check' within the RECORDING sequence. If the automatic drift check passes, the trial continues. If it fails, a standard Drift Check is performed, providing the operator with the opportunity to recalibrate if necessary.
The attached example illustrates one approach to implementing this in Experiment Builder.
Simple_PseudoDriftCheck.ebz (Size: 190.82 KB / Downloads: 85)
How the Pseudo Drift Check Example Works
Here is a step-by-step breakdown of how the attached example project is configured:
- Inside the RECORDING seqeunce:
- Present the automatic Drift Check Target and Define a Fixation Area: At the start of the recording sequence, a DISPLAY_SCREEN ACTION is used to presents a target for the participant to fixate on. An Interest Area is also placed around this target to define the boundaries of a gaze-contingent trigger.
- Wait for Fixation within the Defined Boundary: An Invisible Boundary Trigger is set to fire only if the participant's gaze remains inside the Interest Area for 500 ms. If this trigger fires, the trial proceeds as normal.
- Handle Failure to Fixate Within a Time Limit: A Timer Trigger runs in parallel and is set to fire after 4000 ms.
- If the participant fails to fixate the target within that time, this Timer Trigger will fire instead of the Invisible Boundary trigger.
- This sets a variable named 'Should_Recalibrate' to TRUE.
- It also triggers a Recycle Dataline node, which flags the current trial to be repeated.
- If the participant fails to fixate the target within that time, this Timer Trigger will fire instead of the Invisible Boundary trigger.
- Present the automatic Drift Check Target and Define a Fixation Area: At the start of the recording sequence, a DISPLAY_SCREEN ACTION is used to presents a target for the participant to fixate on. An Interest Area is also placed around this target to define the boundaries of a gaze-contingent trigger.
- Inside the TRIAL sequence:
- Check for Recalibration: The experiment flow returns to the main TRIAL sequence.
- A conditional trigger checks the 'Should_Recalibrate' variable.
- If the variable is TRUE, the experiment jumps to a DRIFT_CORRECT node. At this point, the researcher can confirm if drift is still present, and press ESC to enter the Camera Setup screen and recalibrate if necessary.
- A conditional trigger checks the 'Should_Recalibrate' variable.
- Reset and Continue: After the drift correction is complete, an Update Attribute node resets the 'Should_Recalibrate' variable back to FALSE. The experiment then continues, starting with the recycled trial.
- Check for Recalibration: The experiment flow returns to the main TRIAL sequence.