Tool or Method?
When I was learning how to drive, a friend took me to a large parking lot by a mall. It was a late evening, so the lot was almost empty. There he taught me how to start and stop the car, how to speed up, slow down, steer, and use the turn signal and mirrors. By the end of the night, I was pretty good at it. However, before I could take my Dodge Intrepid on real streets (and unleash its true potential), I had to learn how to drive according to the rules of the road, both written and unwritten.
By the same token, just because you can operate an eye tracker does not mean you can or should use eye tracking in your research. Knowing how to turn on the system and where to click to start a recording or obtain a heatmap is not sufficient (see Figure 1.9). You need to know how to apply eye tracking in a way that yields valid and useful insights. This knowledge encompasses planning, preparing, and conducting studies, as well as analyzing and interpreting the collected eye tracking data. Without a sound method, you are in danger of producing meaningless information and attractive but likely misleading visualizations.
FIGURE 1.9 A heatmap is a commonly used (and misused) eye tracking data visualization. It represents the values of a variable (for example, gaze duration) as colors, where the amount of “heat” is proportional to the level of the represented variable.
When you think about eye tracking, you should consider both the tool— the eye tracker—and the methods that allow you to put the tool to good use. Learning how to operate the tool is not difficult because modern eye trackers are much easier to use than those manufactured even a couple of decades ago. Each eye tracker is accompanied by a detailed manual, and additional training is often provided by the manufacturer.
Information on methods, on the other hand, is not as readily accessible. There are several articles and book chapters available, but no one source that consolidates all the knowledge. What motivated me to write this book was the high demand for sound eye tracking methods specific to the field of user experience. But before we get to the methods, let’s first discuss how to decide whether or not to use eye tracking in the first place. And that’s what Chapter 2 is all about.
Summary
• Eye tracking is the process of determining where someone is looking. It can also measure the characteristics of eye movements and of the eye itself.
• Eye tracking is usually conducted with the help of a device called an eye tracker. Most commercial eye trackers work by emitting near-infrared light to determine gaze location based on the relative position of the pupil center and corneal reflection.
• Human eyes jump from place to place a few times per second. The purpose of these jumps, also known as saccades, is to bring visual stimuli into the fovea (a small area of the highest visual acuity on the retina) and thus into focus. Information is extracted during fixations, which are short pauses in-between the saccades.
• Foveal vision spans only the central two degrees of the visual field. The farther away from the fovea, the more blurry and colorless the image becomes.
• Even though eye tracking only captures foveal vision (what we are fixating/focusing on directly), it provides useful information about visual attention because, in most cases, fixation coincides with attention.
• Saccade destinations (i.e., where the next fixation is going to occur) are selected based on a combination of bottom-up and top-down cognitive processes. In other words, where you look depends on the properties of what you are looking at, as well as your goals, experiences, and expectations.
• This book focuses on the application of eye tracking for UX research (design evaluation in particular) rather than for human-computer interaction. Both the device and method aspects of eye tracking are discussed, with a special emphasis on the methods, which help put the eye tracking devices to good use, leading to valid and useful results.
CHAPTER 2
To Track or Not to Track
Qualitative Insight: Detecting and Explaining Usability Issues
Quantitative Insight: Measuring Differences
In Search of the Simplest Solution
Using Eye Tracking to Gain Stakeholders’ Buy-In
Many UX practitioners seem to be divided into two opposing camps: those who are pro eye tracking, and those who are against it. The proponents seem to want to use eye tracking for every study, regardless of its objectives. The opponents, on the other hand, claim that eye tracking is just “smoke and mirrors” and does not have much value. As is generally the case, the truth lies somewhere in the middle. Eye tracking can be a valuable addition to some UX research and ineffective, or even wasteful, in other cases.
The Three Questions
The decision about whether or not eye tracking is appropriate for a study boils down to three questions. Figure 2.1 illustrates the process I go through when considering eye tracking as a method for a study. Typically, this is an implicit exercise unless I have to explain to the stakeholders why using eye tracking is or isn’t a good idea.
FIGURE 2.1 A set of questions to determine whether or not eye tracking is a suitable method for a research study.
The first and most important question is “Will eye tracking generate actionable insight that addresses my study objectives?” This is not to be mistaken for “Will eye tracking tell me something I don’t know?” Eye tracking will almost always reveal something new and perhaps even interesting, which is undoubtedly tempting. However, that insight may not be able to inform any decisions that have to be made based on the research findings. To justify using eye tracking in your study, your answer to the first question should be “yes.” But that’s not enough. There are two more questions, and you need at least one more “yes” to proceed.
The second question encourages the researcher to reflect on the economy of the selected approach: “Is