Eyetracking Gaze Trigger
Table of Contents
Overview
The Eyetracking Gaze trigger fires every time Labvanced's webcam eye tracking predicts a new gaze location for a participant, whether or not eye tracking is restricted to a specific frame or object.
Note: All processing occurs client-side, ensuring GDPR compliance and guaranteeing that no facial data is ever transmitted or stored externally.
Triggers on:
- Overall: this trigger applies whenever eye tracking has been enabled for the task.
- Only when looking at specific elements: restrict the trigger to fire only when the participant's gaze lands on stimulus objects you have added as targets.
Recording Gaze Data
Upon selecting the Eyetracking Gaze trigger in the Event Wizard and naming the event, a dialog box appears prompting you to auto-create the recording action:
Accepting Record gaze timeseries [X,Y,T,C] (checked by default) creates a Set / Record Variable action using the Coord. + Time + Confidence [X,Y,T,C] Array trigger-specific value described below, with Record Type set to All changes / time series so every gaze update is captured rather than just the final value per trial. A second option, Record per-eye gaze + confidence [Lx,Ly,Lc,Rx,Ry,Rc,T] Array (unchecked by default), instead records the left and right eye's coordinates and confidence separately, using the trigger-specific value of the same name described below.
Preview of Gaze Data Collected in Labvanced
X: X-coordinate of gaze; Y: Y-coordinate of gaze; T: Timestamp; C: Confidence Interval
Enabling / Activating Eye Tracking
In order for the Eyetracking Gaze trigger to function, eye tracking must be activated and enabled under both Settings and Task Controls, as explained below.
Study Settings - Enable Eye Tracking
In the Settings tab, navigate to Physiology → Eye-Tracking and check the checkbox to activate webcam eye tracking for your study. See How to Choose Eye Tracking Calibration Settings for the calibration decisions that go with this.
Task Settings - Enable Eye Tracking
Under Task Controls in the task editor, navigate to the Physiological Signals tab and check Enable Eye-Tracking: for eye tracking to be active in that particular task:
Upon checking Enable Eye-Tracking:, a dialog box also appears prompting you to auto-create recording events for both gaze and fixation together, along with which frames the recording should occur on:
Trigger-specific Values for Gaze
Upon selecting the Eyetracking Gaze trigger, the following options are available in the Value-Select Menu:
| Trigger (Eyetracking Gaze) Options | Description |
|---|---|
Coordinate X | The value of the gaze's X coordinate. |
Coordinate Y | The value of the gaze's Y coordinate. |
Coordinate [X,Y] Array | The gaze coordinates X,Y in an array format. |
Stimulus Name | The name of the stimulus that initiated the gaze trigger. |
Stimulus Info | The stimulus information behind the stimulus that initiated the gaze trigger. |
Camera Capture Time T | The adjusted timestamp of when the camera actually captured the image. In Labvanced's eye tracking pipeline, a camera snapshot happens before the algorithm performs gaze calculations, so Camera Capture Time T is the more accurate timestamp to use than a trigger or recording timestamp. |
Gaze Confidence C | Ranges from 0 to 1; the confidence and probability that there is an open eye in the image snapshot, serving as a blink detector. See Kaduk et al., 2024 for more detail. |
Coord. + Time [X,Y,T] Array | An array containing the gaze coordinates and the camera capture time. |
Coord. + Time + Confidence [X,Y,T,C] Array | An array containing the gaze coordinates, camera capture time, and gaze confidence. This is the recommended value for most studies, and what the automated event setup above creates by default. |
Per-Eye Gaze + Confidence + Time [Lx,Ly,Lc,Rx,Ry,Rc,T] Array | An array containing the left and right eye's coordinates and confidence separately (Lx,Ly,Lc,Rx,Ry,Rc), plus the shared camera capture time. Only populated on eye tracking models that report both eyes independently; records as an empty array on older eye tracking versions, single-output models, or during momentary face loss. |
Trigger Timestamp (Unixtime) | The timestamp of when the gaze trigger occurred, in Unix time with milliseconds. |
Trigger Time (From Frame Onset) | The elapsed time in milliseconds from the frame onset to when the gaze trigger occurred. |
Practical Examples Featuring the Eyetracking Gaze Trigger
Walkthrough - Study Building
For worked examples that use this trigger, see the Eyetracking Walkthrough or Webcam Eye Tracking Demo: SVGs as AOIs, which restricts the trigger to specific stimulus objects using Polygon and SVG masks.
This study measures visual preference and attentional bias using gaze tracking. Participants view social and non-social stimuli while fixation behavior, head movement, and video recordings are captured for analysis.
This study measures cognitive control and stimulus-response compatibility using the Simon Task. Participants respond to stimulus color while ignoring spatial position, allowing measurement of the Simon effect through reaction time and accuracy.
Further Reading
Recording and Exporting Gaze Data
Building this trigger into a full recording setup, and reading the resulting data export.
Eyetracking Fixation Trigger
The sibling trigger for when a participant's gaze settles on a location, rather than every gaze sample.
Using Shapes as Areas of Interest (AOI)
Restricting this trigger to specific stimulus objects using Polygon and SVG masks.