Eyetracking Fixation Trigger

Table of Contents

Overview

The Eyetracking Fixation trigger fires when a participant's gaze settles on a location for a sustained period, rather than firing on every individual gaze sample the way the Eyetracking Gaze trigger does. It is currently in beta.

Note: All processing occurs client-side, ensuring GDPR compliance and guaranteeing that no facial data is ever transmitted or stored externally.

Which fixations get detected, and how quickly, depends on the Fixation Detection mode configured for the task: Real-Time Fixations (faster, more short-duration fixations) or Lagged Optimized Fixations (higher accuracy, better for longer fixations). See Setting Up Eye Tracking in a Task for the full set of Fixation Detection options, including what happens to a fixation still being calculated when a frame or trial ends.

Recording Fixation Data

Upon selecting the Eyetracking Fixation trigger in the Event Wizard and naming the event, a dialog box appears prompting you to auto-create the recording action:

Accepting Record fixation timeseries [X,Y,Dur,Start,End,Disp] (checked by default) creates a Set / Record Variable action using the [X, Y, Dur, Start, End, Disp] trigger-specific value described below. If the task's Fixation Detection mode was set to No Fixation Detection, accepting this option switches it on automatically, since the trigger cannot report fixations without it.

Enabling / Activating Fixation Detection

Fixation Detection is a task-level setting, not a study-level one. Under Task Controls in the task editor, navigate to the Physiological Signals tab, with Enable Eye-Tracking: already checked:

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

The Fixation Detection section of the Physiological Signals tab. Requires the study's Physiology Toolbox Version to be v1.2 or higher.

Checking Enable Eye-Tracking: also triggers a dialog box prompting you to auto-create recording events for both gaze and fixation together, along with which frames the recording should occur on:

Eyetracking Setup dialog offering to automatically create gaze and fixation recording events

The Eyetracking Setup dialog, offering to automatically create the gaze and fixation recording events across all frames, or a single selected frame. See the [Eyetracking Gaze Trigger](./eyetracking-gaze-trigger.html) page for the sibling gaze recording option shown here.

Trigger-specific Values for Fixation

Upon selecting the Eyetracking Fixation trigger, the following options are available in the Value-Select Menu:

Trigger (Eyetracking Fixation) OptionsDescription
Fixation Centroid XThe center point of the fixation as an X value.
Fixation Centroid YThe center point of the fixation as an Y value.
Fixation DurationThe duration of the detected fixation.
Fixation Start TimeThe start time of the detected fixation.
Fixation End TimeThe end time of the detected fixation.
Fixation DispersionHow dispersed the gaze values are within a detected fixation.
Stimulus NameThe name of the stimulus object which triggered the event.
Stimulus InfoThe stimulus info of the object which triggered the event.
[X, Y, Dur, Start, End, Disp]An array of the fixation's centroid X/Y, duration, start time, end time, and dispersion value. This is what the automated event setup above creates by default.
Trigger Timestamp (Unixtime)The timestamp of when the fixation trigger occurred, in Unix time with milliseconds.
Trigger Time (From Frame Onset)The elapsed time in milliseconds from the frame onset to when the fixation trigger occurred.

Practical Examples Featuring the Eyetracking Fixation Trigger

Walkthrough - Study Building

For a worked example that counts fixations on specific AOIs, see the Webcam Eye Tracking Demo: SVGs as AOIs walkthrough, which uses a Polygon shape as a fixation-counting trigger.


Preferential Looking Test

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.

Simon Task with Eye Tracking

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

Eyetracking Gaze Trigger

The sibling trigger that fires on every individual gaze sample, rather than detected fixations.

Setting Up Eye Tracking in a Task

The full set of Fixation Detection modes and how they affect this trigger.

Using Shapes as Areas of Interest (AOI)

Restricting this trigger to specific stimulus objects using Polygon and SVG masks.