Why Should You Care Where People Look?
Why Do People Look at What They Look At?
Eye tracking, which is the process of identifying where someone is looking and how, has generated a great amount of interest in the user experience (UX) field since the beginning of the twenty-first century when the technology started becoming more widely accessible. Once a novel addition to the UX research toolbox, used by only a handful of early adopters, eye tracking is now frequently employed to help evaluate and improve designs (from websites to product packaging) at various stages of the development cycle.
Because it captures behaviors that are not easily controllable (by study participants) or observable (by researchers), eye tracking has been perceived as both more scientific and more “magical” than conventional usability testing methods. Initially, this perception resulted in eye tracking frequently being used for its own sake, regardless of study objectives. The common belief was that any study would produce better insight if accompanied by eye tracking.
When I started applying eye tracking to UX research in 2003, the typical approach in the field seemed to be “ready, fire, aim” or “track now, think later,” as we used to fondly call it. Practitioners would often turn on their newly acquired eye trackers and collect eye movement data with no consideration for the study design or the outcome. They would then embark on a fishing expedition, looking for data that might address their questions, failing to realize that they should have structured their study differently to obtain meaningful results.
While the mentality of eye tracking as the “be-all end-all” and the “tracknow-think-later” approach still exist to some extent, more and more practitioners realize that in order to learn something useful from eye tracking, more emphasis must be placed on science and less on magic. They recognize the importance of being aware of both the capabilities and limitations of eye tracking, knowing how to properly incorporate it into UX research, and learning how to interpret and communicate eye tracking findings. This book covers all these topics, but before we start diving into deep waters, let’s first examine the concept behind eye tracking.
A Quick Look Back
Eye tracking as a technique originated in reading research. Researchers in the late 1800s realized that people’s eyes didn’t move as smoothly through text as it had always been assumed. This (unaided) observation prompted researchers to develop technology to measure eye movements in an effort to better understand how people read.
The first eye tracking devices appeared in the early 1900s. These eye trackers were intrusive because they relied on electrodes mounted on the skin around the eye or on the use of large, uncomfortable contact lenses that study participants had to wear. Non-intrusive eye tracking techniques started emerging shortly thereafter. They involved recording light that was reflected on the eye or filming the eyes directly.
The advances in eye tracking technology since then have focused on reducing the constraints posed by eye trackers on research participants, while increasing the precision and accuracy of these devices, as well as making data analysis easier. At the same time, eye tracking research has deepened researchers’ understanding of the relationship between the different aspects of eye movements and the human cognitive processes.
The first application of eye tracking to UX-related research dates back to 1947, when Paul Fitts and his colleagues investigated how pilots used the information provided by instruments in the cockpit to land a plane.1 At the time, however, eye tracking was still primarily used by academic and medical researchers. It wasn’t until the late 1900s and early 2000s when the technology, mostly due to its improved affordability and usability, became more widespread among practitioners.
To learn more about the evolution of the eye tracking technology and details of how it works, you should check out Duchowski’s Eye Tracking Methodology.2
What Is Eye Tracking, Anyway?
You are hopefully reading this book not because you want to build an eye tracker, but because you want to make use of eye tracking in your research. If that is the case, you do not need to know exactly how the hardware works to be successful in using it, just like you do not need to know what is under the hood of your car to be a good driver. However, as a professional, you should be at least somewhat well versed on the topic.
If you are already involved in eye tracking research, then you probably know what I mean. I am often asked about how eye tracking works by research stakeholders, other UX practitioners, study participants, and even my friends. And how can I blame them for their curiosity? Eye tracking is indeed fascinating.
Imagine that someone at a party overhears you mentioning eye tracking. Let’s call him John.
JOHN (wrinkling his forehead): Eye tracking? What is that?
YOU: Eye tracking is the process of determining where someone is looking. It can also measure the characteristics of eye movements and the eye itself, such as the size of the pupil. To conduct eye tracking, you need special equipment called an eye tracker.
JOHN: An eye tracker?
YOU: Yes, an eye tracker. It’s a piece of hardware that records your eye movements as you look at a computer screen, a physical object, or even your surroundings in general. Some eye trackers are affixed to a pair of glasses or a special hat you can wear. Others can be placed in front of you, like those that are attached to computer monitors.
JOHN: This sounds pretty cool. But how does it work?
YOU: The eye tracker shines infrared light onto your face, and then it records two things: the reflection of the infrared light from the retina, which helps find the center of your pupil, and the reflection of the infrared light from the cornea, which is called corneal reflection.
JOHN: Retina? Pupil? Cornea? You kind of lost me there.
YOU: The retina, pupil, and cornea are parts of the eye. Let me show you the eye diagram that I carry in my wallet for occasions such as this one (proudly taking the eye diagram from your wallet [see Figure 1.1]). The retina is a light-sensitive tissue in the back of the eye. The pupil is a black-looking opening that allows light to enter the retina. The cornea is the transparent front part of the eye.
FIGURE 1.1 The human eye.
JOHN (nodding): Uh-huh.
YOU: If you look at my eyes