result in actionable findings. Use eye tracking only when it can provide insight to inform a design or business decision. Don’t use it just because the findings could be interesting.
• Eye tracking can benefit formative testing by improving design recommendations through:
• Detecting usability problems in the absence of other more conventional indicators such as participant behavior and feedback.
• Revealing the source of problems that have been detected with other methods (for example, it can explain why participants made an incorrect action, failed to understand something, or took longer than expected).
• In summative research, eye tracking can help inform decisions such as which design version to choose or whether or not to launch a product. It does that by providing ways to measure and compare products along:
• Performance-related dimensions (for example, search efficiency, ease of information processing, and cognitive workload).
• Attraction-related dimensions (for example, noticeability, interest, and emotional arousal).
• Even when eye tracking is able to answer your research questions, be aware that other research methods may provide answers more quickly, cheaply, or directly. This is often the case in formative usability testing focused on finding problems and improving the design. However, the use of eye tracking may still be justified if your research can benefit from the added pizzazz in convincing stakeholders of usability problems to affect change.
PART II
Study Preparation
CHAPTER 3
Eye Trackers and Other Necessary Resources
Not All Eye Trackers Are Created Equal
Technical Specs You’d Probably Rather Not Know About
Why, in the End, Specs Don’t Matter So Much
If you have decided, based on your undoubtedly thorough reading of Chapter 2, “To Track or Not to Track,” that eye tracking is indeed an appropriate method for your study, there are a few things to consider before you start putting together the study test plan. As you can imagine, using eye tracking requires some additional resources. This chapter will help you figure out what you will need for eye tracking in addition to the tools and other resources you already use for your non-eye tracking UX research.
Not All Eye Trackers Are Created Equal
The first thing you will obviously need is an eye tracker, but not just any eye tracker. You should make sure that the eye tracker you choose to use is suitable for what you are testing and where, for your research objectives, and for the type of participants that will be invited to the study.
Remote vs. Wearable Eye Trackers
There are two main types of eye trackers used in UX research: wearable (see Figure 3.1) and remote (see Figure 3.2). The main difference between the two is the location of the equipment during tracking. Wearable eye trackers are worn on a participant’s head, while remote eye trackers are contact-free and placed in a fixed location in front of a participant. Table 3.1 compares remote and wearable eye trackers based on their uses, advantages, and limitations.
FIGURE 3.1 Examples of wearable eye trackers.
FIGURE 3.2 Examples of remote eye trackers.
TABLE 3.1 A COMPARISON OF TWO MAIN TYPES OF EYE TRACKERS
| Remote Eye Trackers | Wearable Eye Trackers | |
| Setup | Placed in a fixed location in front of a participant (e.g., on a desk or a car dashboard). | Worn on a participant’s head (e.g., as a pair of glasses, attached to a hat, or on a headband). |
| Application | Used in studies during which participants can sit or stand in one place and the stimulus is presented on a stationary surface (e.g., research using on-screen stimuli such as websites, images, and video). | Used in studies that require participants to move around and interact with physical objects or people (e.g., wayfinding, shopping, and out-of-the-box research). |
| Obtrusiveness | Less obtrusive than wearable systems—participants can easily forget about the eye tracker during the study. | More obtrusive because the system has to be worn on the head and is usually partially visible to the participant (even though people learn to ignore it after a while). Also, headgear may be undesirable due to hygiene or hairstyle concerns. |
| Freedom of Movement | Participant must be positioned in front of the eye tracker and only limited head movement is acceptable. There also has to be a clear path between the participant’s eyes and the eye tracker (e.g., a participant cannot hold anything in front of his face). | Participant can move around freely and manipulate objects. However, most wearable eye trackers work best for objects that are at the same distance as the calibration, and are less accurate for objects that are closer or farther. This is called a parallax error and only some systems can correct for it. |
| Ease of Analysis |
Because the recorded scene doesn’t change with head movement, the same gaze location in the recorded frames indicates the same object in the world. Data analysis is typically easier and faster because more automated data mapping and aggregation are possible.
However, that’s only the case for static stimuli. If the content is dynamic (e.g., a video or a website with a lot of overlays), the lack of a stable coordinate system can make the analysis
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