Setting Up Eye Tracking in a Task

Once eye tracking is enabled for your study (see How to Choose Eye Tracking Calibration Settings), you still need to enable and configure it for each individual task where you want gaze data collected.

Task Settings dialog showing the Physiological Signals tab, the Enable Eye-Tracking checkbox, and the Drift Correction fields

Enabling Eye Tracking for a Task

In the task editor, click the Settings button in the top-left corner, next to "Task:". In the dialog that opens, go to the Physiological Signals tab and check Enable Eye-Tracking:.

Eye tracking can be enabled for multiple tasks within the same experiment. The main calibration, configured at the study level, only runs once, before the first task in the study that has eye tracking enabled. Every subsequent task with eye tracking enabled uses the recalibration settings described below instead of running a full calibration again.

Recalibration and Drift Correction

Once eye tracking is enabled for a task, four fields control how the system keeps gaze predictions accurate over the course of that task:

  • Number of points shown: how many recalibration points are displayed before the task begins. Set to 0 to disable recalibration entirely. Defaults to 7.
  • Show recalibration before every: how many trials pass before recalibration runs again. Defaults to 7.
  • Number of points used: how many of the shown points are actually used in the recalibration calculation, which can be set higher than the number shown.
  • Directly apply/subtract drift values from gaze data: when enabled, corrects a participant's gradual, natural tendency to drift in one direction over the course of a task.
    • Adaptive Mode: when this sub-option is enabled, drift correction is applied or withheld automatically based on a cross-validation check, rather than always being applied.

If your task is short, or gaze accuracy is not critical to your measure, disabling recalibration (Number of points shown set to 0) keeps the task moving faster for participants. For longer tasks, or ones where small errors in gaze position matter, the default recalibration settings help correct for accuracy drifting over time.

Fixation Detection

Fixation Detection determines how Labvanced identifies when a participant's gaze has settled on a location, rather than just reporting a raw stream of gaze coordinates. It requires the study's Physiology Toolbox Version to be set to v1.2 or higher.

Task Settings dialog showing the Fixation Detection section, with Fixation Algorithm and Conclude Ongoing Fixations options

  • No Fixation Detection: disables fixation analysis; only raw gaze coordinates are collected.
  • Real-Time Fixations: fixations are calculated as gaze data arrives, with about a 50 millisecond lag. Best for studies that need immediate participant feedback based on fixations, such as gaze-contingent displays.
  • Lagged Optimized Fixations: fixations are calculated after observing subsequent gaze points, with about a 500 millisecond lag, producing higher accuracy and better detection of longer fixations. Best when feedback can be slightly delayed, or for post-experiment analysis.
  • Conclude Ongoing Fixations: controls what happens to a fixation still being calculated when a frame or trial ends before the algorithm finishes. Options are to keep the buffer running across frame/trial boundaries, or to force the fixation calculation to conclude at the end of the frame or the trial. Forcing conclusion is useful when you need to know whether a participant fixated on a target before moving to the next frame or trial.

Display Settings

The default display mode is Zoom / Adaptive, which scales your task's content to fit each participant's screen. For eye tracking tasks, switching to Fixed in Visual Degree or Fixed in Millimeter is often preferable, since gaze position is then reported in a physical unit rather than in frame units that vary by screen size, making measurements comparable across participants.

If you switch to Fixed in Visual Degree or Fixed in Millimeter for any task in your study, the Measure Screen Size (card calibration) option under Settings tab → Controls → Screen becomes mandatory and cannot be disabled. This asks participants to hold a standardized card (85.60 by 53.98 mm, the size of a credit card or ID card) up to their screen so Labvanced can calibrate the physical screen size, which is what makes millimeter and visual-degree measurements accurate in the first place.

Restricting Tracking to Specific Stimulus Objects

You can also limit a gaze or fixation event to fire only when the participant looks at specific stimulus objects, rather than anywhere on the frame. This is configured as part of building the event itself, covered in Recording and Exporting Gaze Data.

Worked Examples

For a full worked example of building a study around these settings, see the Eyetracking Walkthrough or the infant-friendly Object Discrimination Task walkthrough. Both reflect an older version of the settings interface, so field names and screenshots may not match what is described above, but the overall structure of the walkthroughs still applies.

Frequently Asked Questions

If I enable eye tracking for multiple tasks in the same experiment, does full calibration run every time?
No. The main calibration, configured at the study level, only runs once, before the first task in the study that has eye tracking enabled. Every subsequent task with eye tracking enabled uses that task's recalibration settings instead.
Can I disable recalibration for a short task?
Yes. Setting `Number of points shown` to 0 disables recalibration entirely for that task, which keeps things moving faster for participants when the task is short or gaze accuracy is not critical to your measure.
Which Fixation Detection mode should I use if I need to react to a fixation immediately, mid-task?
`Real-Time Fixations`. It calculates fixations as gaze data arrives, with about a 50 millisecond lag, and is best for studies that need immediate participant feedback, such as gaze-contingent displays. `Lagged Optimized Fixations` produces higher accuracy but with about a 500 millisecond lag, which suits post-experiment analysis better than in-task feedback.
What happens to a fixation that hasn't finished calculating when a trial ends?
It depends on `Conclude Ongoing Fixations`. You can either let the buffer keep running across the frame or trial boundary, or force the fixation calculation to conclude at the end of the frame or trial, which is useful when you need to know whether a participant fixated on a target before moving on.
Do I need to set up the Measure Screen Size card calibration if I'm using the default display mode?
No. `Measure Screen Size (card calibration)` only becomes mandatory once you switch a task to `Fixed in Visual Degree` or `Fixed in Millimeter`. The default `Zoom / Adaptive` mode does not require it.

Further Reading

Recording and Exporting Gaze Data

Build the events that capture gaze data as recorded variables, and access the resulting export.

Presenting Stimuli in an Eye Tracking Task

How stimuli relate to eye tracking, before you get into task settings.

How to Choose Eye Tracking Calibration Settings

The study-level calibration settings that this task's recalibration builds on.