Introduction

With eye tracking one can obtain information about a person's gaze (where someone is looking) and pupil size.

Availability, Support and Use-case

At the FSW Leiden mainly Tobii and EyeLink eye trackers are used. At the LIBC MRI Scanner an EyeLink eye tracker can be used.

Getting Started with Eye Tracking

Below you will find some useful links per eye tracking topic.

Eye Tracking Overview

• Book: Eye tracking: a comprehensive guide to methods and measures
  (Holmqvist, K., Nyström, N., Andersson, R., Dewhurst, R., Jarodzka, H., & Van de Weijer, J. (Eds.) (2011). Eye tracking: a comprehensive guide to methods and measures. Oxford, UK: Oxford University Press.)
• Book: Eye Tracking Methodology 
  (Duchowski, A. T. (2017). Eye Tracking Methodology: Theory and Practice. Springer.)
• Article: Best practices in eye tracking research
• Article: Eye tracking: empirical foundations for a minimal reporting guideline
• Tobii Webinar: Conducting successful eye tracking studies
• Tobii Article: Types of eye movements

Tobii

• More information can be found on this wiki about:
  • Tobii eye trackers
  • Tobii Pro Lab
  • Tobii Pro Eye Tracker Manager
  • Tobii software guide
  • Tobii troubleshooting
  • Using a Tobii eye tracker with E-Prime or OpenSesame, or Tobii Pro Lab with E-Prime
• Tobii website
• Tobii Academy
• Tobii Webinar: Using eye tracking for your screen-based study
• Tobii Webinar: A beginner's guide to a wearable eye tracking study
• Tobii Webinar: Introduction to Tobii Pro Lab

EyeLink

• More information can be found on this wiki about:
  • EyeLink eye trackers
  • Using an EyeLink eye tracker with E-Prime or OpenSesame
• EyeLink forum (you need to register to be able to view forum threads)

Pupil data

• Tobii Webinar: Power of the pupil
• Pupil data analysis with the PhysioData Toolbox
• EyeLink pupil size is reported in an arbitrary pixel unit, but can be converted to mm, see video and instructions. Note that when you want to obtain pupil data with EyeLink, a chinrest must be used.

Calibrating an eye tracker

• Tobii Article: Eye tracker calibration and validation
• Tobii Article: Accuracy and precision

Tips & Tricks

• Good calibration: A good calibration of the eye tracker is important when you want to obtain high quality data. Make sure to familiarize yourself with the calibration procedure, and adjust the calibration according to the participant (e.g. when calibrating the eye tracker with children, less calibration points and/or video's can be used for the calibration.
• Light conditions: Most eye trackers use near-infrared light to obtain information about reflections of this light on the eye and then use this information to be able to track the eye. To obtain the best quality of data it is highly advised to not have direct light shining in the eye tracker or in the participant's eyes. Other than that, it is recommended that the space in which eye tracking is done is not very bright or very dark.
• Reporting data quality: It is highly advised to report data quality. Data quality can be reported in terms of accuracy and precision (see also Best practices in eye tracking research and Tobii article about accuracy and precision). The percentage of valid gaze samples can also be reported. Make sure that you know how your eye tracking data collection software saves this information, or how this information can be obtained.
• Mapping screen-based eye trackers to screen: The Tobii screen-based eye trackers (Fusion, X3-120, X2-60) need to be mapped to the screen, which is done with the Tobii Pro Eye Tracker Manager (see Tobii Pro Eye Tracker Manager for instructions).