Introduction

This manual provides a step-by-step guide for researchers using a Tobii screen-based eye tracker. It covers participant screening, hardware setup, software configuration, data collection, data export, and equipment maintenance.

Learning Goals

By the end of this training you will:

• Know how to set up a screen based Tobii eye tracker
• Understand the software involved for setting up an eyetracker
• Know how to set up a basic experiment and collect data with Tobii Pro Lab

Participant Characteristics

Before scheduling participants, it is important to determine whether accurate eye tracking is likely to be possible.

Exclusion Criteria

• Wearing corrective lenses, particularly, bifocal or multifocal glasses
• Having undergone eye surgery, including corneal or cataract surgery, or having an intraocular lens implantation
• Have eye movement or alignment abnormalities, such as strabismus, nystagmus, or another eye movement disorders

Preferred Vision Correction

• Contact lenses are generally preferable to glasses for eye tracking, if participants are comfortable with wearing lenses

Additional Considerations

• Ask participants to avoid heavy eye makeup, false eyelashes or coloured contact lenses
• Some eyes can be more difficult to track, including those with droopy eyelids, very long eyelashes, or highly reflective glasses

Step-by-Step Training Plan

Before Testing

Hardware Setup

Pre-Setup: If using a Tobii that has an external processing unit (X2-60 or X3-120) together with a laptop without an ethernet port, you need an adapter to connect the ethernet cable to your laptop.

Mounting the Eye Tracker

1. Open the mounting diagram Tobii Eye Trackers - SOLO Research Wiki for the respective eye tracker you are using.
2. Mount the eye tracker beneath the monitor by attaching it to the magnetic strip that is attached to the screen.
3. Verify that all cables are securely connected and the setup is connected to a power socket.

Initial Eye Tracker Configuration

Before opening Tobii Pro Lab, verify that the eye tracker is functioning correctly.

1. Launch Tobii Eye Tracker Manager.
2. Select your eye tracker in the top left corner. Note that it can take a while before the eye tracker appears after connecting it to your PC.
3. Check the Display Setup: Select the desired display setup or click on the three dots and click New if it still needs to be configured. A detailed explanation can be found here: Setup New Screen in Tobii Pro Eye Tracker Manager

Optional:

• Position Guide: Use the Position Guide to verify your desk setup and the position of the participant before testing. The eye tracker needs to detect the participant, and the participant needs to be seated within the tracker's optimal tracking area. This is indicated by the position guide turning green and showing the head schema.
• Calibration: Eye Tracker Manager includes a calibration option. However, for most studies, calibration should be performed later within Tobii Pro Lab (or other software used for data collection).

Participant Positioning & Testing Environment

Participant positioning

• Participant positioning has a major influence on calibration quality and tracking accuracy. Provide a stable chair without wheels whenever possible, let participants take a comfortable seating position with easy access to the keyboard and mouse if required.
• The participant should sit upright, remain relaxed, and maintain a stable position throughout the recording. The recommended distance from participants to screen is approximately 60 cm.
• During data collection and especially during calibration/validation, participants should keep their head as still as possible, avoid unnecessary movement, and not talk.

Testing environment

• Lighting: Ensure that the room is not too bright and not too dark, no direct light shines into the participant's eyes, no direct light shines onto the eye tracker, and participants are not seated directly beside a sunny window.
• It is recommended to close curtains if possible and ensure consistent lighting conditions throughout testing.
• Note: For gaze position data, small variations in lighting are usually not critical. For pupil size measurements, lighting should be kept as consistent as possible because pupil diameter is strongly affected by illumination.

Testing with Tobii Pro Lab

Introduction to Tobii Pro Lab

Tobii Pro Lab is a software that can be used to design your experiment (basic), and to record and analyse data. Watch the Tobii Pro Lab introductory video before creating your first project. This manual does not give a complete training for Tobii Pro Lab, but rather puts the focus on important components. For a full training, please visit the Tobii Academy. You will have to create an account for this and fill in a serial number, which you can receive from lab support. You can find more detailled information on Tobii Pro Lab and a general overview for errors that are often encountered in the Tobii FAQ on the SOLO Research Wiki.

Starting Up

Creating a New Project

• Screen-Based Project: Use when simple visual stimuli, such as pictures, video, text and websites on a screen are presented directly through Tobii Pro Lab.

• Advanced Screen-Based Project: The Advanced Screen Project allows for presenting multiple stimuli on one screen and allows for managing many trials and media with the help of Excel sheets. Data is collected with a screen-based eye tracker.

• External Presenter: The External Presenter project enables you to use third-party software to manage the stimulus presentation. This means that you can build and run your experimental task in E-Prime, OpenSesame or PsychoPy while Tobii Pro Lab runs in the background. The eye tracking data and stimuli are sent to Tobii Pro Lab, so that the data can be analyzed with Tobii Pro Lab.
• Glasses Project and Scene Camera Recording are neglected for now.

When selecting a project storage location, do not save projects to network drives (such as OneDrive), rather save on C:\ExperimentData.

Open an Existing Project

Select your project from the list or click Browse to open your project. After clicking Browse, open the project folder, which contains a folder called Data and a Project File called tobii.project. Select the tobii.project file to open. Ensure that the Data folder and the tobii.project file are always in the same folder, not in two separate places.

ProjectXYZ - Project Overview

• After creating a project or opening an existing one, you see the Project Overview with your recordings (if any).
• The panel on the side allows you to view and add different project components. For example, you can add Participant variables, such as Participant ID, Age, or Gender. These variables function similarly to a questionnaire and are asked before the task starts. Unfortunately, this is not an open field, but you need to predetermine the answer options (which is unhandy with for example ‘age’). Another is the Custom Event Types, which will allow you to set up hotkeys to mark certain events, such as participant movements, in your data.

Design Tab - Creating or Editing a Project

• It is important to set or check the Presentation resolution in the top left. This must match the Windows display settings of the screen(s) where the experiment will run. We generally recommend 1920 x 1080. You can see these settings when going to your Desktop ➡ right-click and select Display settings ➡ adjust the resolution to 1920 × 1080 and windows scaling: 100%. It is recommended to use this resolution for all the screens you are using.
• In the timeline, a Calibration element is already added.
  • You can choose the number of calibration targets. The recommended setting is a 5-point calibration. Fewer points may be useful for young children or any other participants with limited attention spans.
  • There are different calibration targets available. Options include status point (standard), animated target, and video target.
  • Select the option “Validate calibration”, if not pre-selected. Always perform a validation immediately after calibration. Validation provides accuracy and precision metrics and helps determine whether calibration quality is sufficient.
• Stimuli such as images, videos, text, and websites can be added from this toolbar.
• Stimuli can also be organized into Groups, which allows for basic trial randomization.

• It is possible to create multiple Timelines, so that you can present multiple tasks in one project or counterbalance different timelines between participants.
• Limitation: Tobii Pro Lab is not intended for advanced interactive experiment programming. If extensive interaction or custom logic is required, use an external presenter such as PsychoPy or E-Prime.
• More detailed explanations on how to program your experiment can be found in the Tobii Pro Academy.

Record Tab - Recording Data

Here, you can select the desired Timeline to present.

• On the top-left, select the eye tracker (if not already pre-selected).
• Presentation screen field: Select the presentation screen. When using extended displays, make sure that the participant screen is the screen with the attached eye tracker.
• Participant field: Select the participant (or create a new one).
• Recording field: Create a recording name.
• If required, allow Tobii Pro Lab to prepare the timeline by clicking Prepare Timeline.
• Before starting the recording:
  • Position your participant according to 4. Participant Positioning & Testing Environment.
  • Instruct your participant to follow the dot/animation on the screen with their eyes for the calibration and validation measurements.
• Click Start recording to begin. Calibration and validation will start.
  • Interpreting Results
  • Acceptable values depend on the research question, the stimulus size, and the area of Interest (AOI) size. In general, smaller AOIs require better accuracy and precision, while larger AOIs may tolerate lower calibration quality.
  • If the calibration and validation results are not satisfactory, they can be repeated. If the measures stay poor, then it is recommended to just start testing. The eye tracker has difficulties picking up some participant characteristics.

Analyze Tab - Data Analysis and Export

In Tobii Pro Lab, tools to analyze data include visualizations, AOI tools, metric exports, and data exports.

• When selecting the Analyze tab, you can decide to either select a single recording or a summary measure such as Visualizations and AOI-tools.
• Click on a recording to review it. Here, Events and Times of Interest (TOI) can also be viewed or created.
• Metrics Export: Use when exporting summary measures such Total fixation duration, time to first fixation, visit count and AOI-based measures.
• Data Export: Use when exporting raw data. Exports can be created in formats such as TSV or XLSX.

Important: Exporting data is different from exporting a project backup.

• Project Export creates a project archive. You need Tobii Pro Lab to open these files again. You can export the project in the Project Overview.
• Data Export or Metrics Export creates files with raw, pre-analyzed or summarized data for statistical analysis. You can export data or metrics via the Analyze tab.

Project Management and Backups

Before completing a data collection session:

1. Click Export Project in the project overview and select the type of export you need.
2. Create a backup ZIP file.
3. Store the ZIP file in a secure location, e.g., on a J drive folder or in your cloud.

The export contains the project structure, tasks, stimuli, and recordings (so data).

Restore data

In case you need to restore your project, you can use this ZIP file.

1. Unzip the exported project.
2. Open Tobii Pro Lab.
3. Select Open Existing Project.
4. Click Browse.
5. Navigate to the extracted folder.
6. Select the file: tobii.project. Ensure the associated Data folder remains in the same directory.

Understanding Calibration and Validation Metrics

In the calibration summary, you see values that describe the quality of your calibration and validation.

• Accuracy: Accuracy represents how close recorded gaze data is to the participant's actual point of gaze. Lower accuracy values indicate better performance.
• Precision: Precision represents the consistency of gaze measurements over time. Higher precision means less noise and more stable data. Lower precision appears as a larger spread of gaze samples around a target.

Gaze Sample Percentage

After finishing the recording, a gaze ample percentage is reported for each recording. Do not infer data quality from this percentage, as this value is calculated over the entire recording period, including calibration, validation, and delays before stimulus presentation. Therefore, this gaze sample percentage is not a reliable indicator of data quality during stimulus presentation.

After the Session

Cleaning the Eye Tracker

After use, gently wipe the eye tracker using the microfiber cloth included in the eye tracker packaging. Do not use alcohol or cleaning solvents, apply excessive pressure, or touch the sensor surface unnecessarily. Proper maintenance helps preserve tracking quality and extends the life of the equipment.

Further Reading

Tobii Software - SOLO Research Wiki

Tobii Eye Trackers (Hardware) - SOLO Research Wiki

Eye Tracking - SOLO Research Wiki