Eye-tracking measures the location and duration of a user’s gaze on stimuli (web page, computer screen, mobile app, etc.), and can provide valuable insight into users’ viewing behaviors. This can unearth usability problems in which elements are being missed.
More broadly, eye tracking is used by UX researchers in various user research methods such as A/B testing and moderated task-based usability testing to see through a user’s eyes and track/record what viewers are looking at and for how long. It also reveals how eyes move and search for information on the screen, which can help identify whether users are attracted to specific content or features.
We should point out that most eye-tracking studies are conducted as moderated studies in an eye-tracking lab under controlled light conditions. However, with eye-tracking technology like portable eye-trackers, it is possible to collect eye movements outside of a lab environment.
Eye-tracking has a broad range of applications and has been used by a number of researchers in UX research, psychology, and neuromarketing to study user behavior. Tracking people’s eye movements can help UX researchers understand the factors that may impact the usability of an interface by detecting where users focus their attention and how they look for information on the interface.
Eye-tracking can be added to a moderated usability study at any time in the product lifecycle/design cycle to obtain objective feedback from users’ viewing behavior. Anytime you need to see exactly what a user is looking at (or not looking at) in real-time during navigation, eye tracking will help.
Most commercially available eye-tracking systems today capture eye movements using an unobtrusive method known as video-based corneal reflection. Eye trackers include infrared light sources and cameras. The light sources send light to the eyes and the exact location of the eyes are measured from the corneal reflection of the eyes on the screen (Fig.1).
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Fig. 1. Image Source: https://www.tobii.com/group/about/this-is-eye-tracking/
It is for these reasons that eye tracking studies are usually conducted in eye tracking labs with controlled light condition; however, portable eye tracking devices could be used to conduct studies outside of the laboratory environment as well.
Keep in mind that eye trackers must be calibrated for each viewer, therefore, each participant needs to complete the calibration process before the start of the eye-tracking study. During the calibration process the eye tracker learns how certain coordinates on the stimulus (e.g., certain coordinates on a computer screen) correspond to a viewer’s eye position. The calibration process allows the eye tracker to associate the viewer’s pupil data with known locations on the stimulus.
Eye tracking devices collect eye movements with different sampling rates from 30 Hz to 1000 Hz. The higher the sampling frequency of the eye trackers the higher the accuracy of eye tracking. Eye trackers with higher sampling rates (>300) are used for more in-depth psychological eye-tracking studies (e.g., to study eye movements in reading.)
Here are essential facts to consider while deciding on whether or not eye tracking is the right approach for your research goals.
Typical metrics obtained from eye-tracking software include duration and location of gaze on the screen (fixations), the trajectory path that eyes travel from one fixation to another (saccades), coordinates of the eyes on the screen (x,y, and z coordinates), and the size of the pupil of the eyes (Fig.2).
Fig. 2. Image Source:http://theconversation.com/what-eye-tracking-tells-us-about-the-way-we-watch-films-19444
The results obtained from an eye-tracking software depends on the eye tracking software though they are typically categorized as the following:
Fig.3. Image Source:http://theconversation.com/what-eye-tracking-tells-us-about-the-way-we-watch-films-19444
In an eye-tracking study the size of the exported data for each participant depends on the sampling frequency of the eye tracking device and the duration of the study. To save processing time in large-scale eye tracking studies it is especially important to choose the right metrics that relate to your research questions.
We also wanted to quote two great pieces of advice from William Albert & Thomas Tullis’ book Measuring the User Experience.
“Only look at time data when the participant is engaged with the task. Do not include any time data when the participant is debriefing about her experience and still being tracked.”
“Be careful when analyzing eye movements on dynamic websites. ”
Finally, if you do decide to run an eye tracking study keep in mind that think-out-loud (TOL) and self-reporting surveys after the task complement eye tracking quite well. This is because combining objective eye tracking data with subjective self-report user’s responses can be beneficial in understanding the user’s conscious or unconscious behavior.