A great deal of research has established that where you place your gaze is typically associated with what you pay attention to and think about,3 especially when looking at something with a goal in mind. This is called the eye-mind hypothesis.
Yet, there are skeptics out there who do not think that knowing where people look can be meaningful in any way. The argument is usually, “I don’t have to look at something in order to see it,” which tends to be followed by, “I’m looking at your face right now, but I can still see the color of your sweater” or something of that nature.
You certainly could direct your attention to the periphery of your visual field. But if you wanted to see what color sweater someone was wearing, you would look directly at it for two reasons: (1) you can see things much more clearly when looking directly at them; and (2) paying attention to something and trying not to look directly at it is unnatural and requires conscious effort. Humans prefer moving their eyes when shifting visual attention, focusing on what they are trying to see. However, when people do not look at something directly, you cannot say for sure that they did not see it. Eye tracking only captures foveal vision, yielding no information about what was noticed peripherally. This is one of the limitations of eye tracking.
Another argument against eye tracking might be this: “People can look at something but not necessarily ‘see’ it.” Yes, that can happen. Close your eyes after you have been talking to someone face to face for a while and ask that person what color your eyes are. Many people will not know, although they have been looking at you (and presumably glancing at your eyes) for a while, and maybe even have known you for years. This is just one example of how you can look at an object but not necessarily register everything about it. Sometimes, you can even miss the entire object itself.
To sum up this discussion, a lack of fixation does not always mean a lack of attention, and fixation does not always indicate attention, but fixation and attention coincide a whole lot. Attention is actually slightly ahead of the eyes because it plans their next destination. Once the eyes move there, attention helps allocate the processing resources to what is being fixated upon. Knowing where users’ attention is directed helps the researcher evaluate and improve products, which is the focus of Chapter 2, “To Track or Not to Track.”
Why Do People Look at What They Look At?
Your visual behavior is influenced by anything that makes you look (bottom-up attention), as well as your voluntary intent to look at something (top-down attention). Bottom-up attention is stimulusdriven. Attention is involuntarily shifted to objects that contrast with their surroundings in some way. For example, bright colors and movement can make you look at something. Things that are new and unexpected in a familiar environment can grab your attention, too.
If bottom-up factors were the only ones influencing people’s attention, everyone would look at the world in the same way, regardless of what they knew and what they were trying to accomplish. This consistency would certainly make your research easier, wouldn’t it? Studying different user groups and multiple tasks would no longer be necessary.
Unfortunately (but also more interestingly), this is not the case, due to the involvement of top-down factors. Top-down attention is knowledgedriven and relies on your previous experience and expectations. You intentionally choose to look at information that you consider relevant to your goals.
You have probably already heard that eye movements are task-dependent. What this means is the same person will look at the same object differently if given a different task. For example, someone looking at mobile phone packaging will generate a different gaze pattern when trying to determine the brand of the phone than when trying to find out if the phone will allow him to browse the Web (see Figure 1.8). It is the top-down attention that is responsible for these differences.
FIGURE 1.8 Left: Gaze plot of a person looking for the brand of the phone. Right: Gaze plot of the same person trying to find out if the phone offers Internet access. Notice how the same person with the same package—but a different task—produced different fixation patterns.
Applications for Eye Tracking
There are two main applications for eye tracking: as a research technique and an input device. As an input device, eye movements become control signals for a computer system, either instead of or in addition to a mouse and keyboard. People with disabilities such as ALS and cerebral palsy use gaze-controlled applications to help them communicate. Gaze interaction is also used in entertainment (for example, gaming) and is making its way into mainstream mobile applications.
The rest of this book focuses on how eye tracking can be applied to research, specifically UX research—an investigation of how people experience products, interfaces, services, or even their surroundings. UX research can be divided along two dimensions: the target of the research and the scope of the research (see Table 1.1). This breakdown results in four categories: Engineering Psychology Research, Design Research, User Research, and Design Evaluation. Eye tracking can be used in all four types of research, but this book is primarily about eye tracking for formative (or diagnostic) and summative design evaluation (the shaded bottom-right quadrant of the table).
TABLE 1.1 BREAKDOWN OF UX RESEARCH
| Target of the Research | ||
| Scope of the Research | ||
| Users | Design | |
| Generalizable across products | Engineering Psychology Research | Design Research |
| (theory-driven and often academic) | Goal: To understand the capabilities and limitations of human perception, cognition, and movement control. Sample research questions: What is the effect of noise on human performance? What factors impact how well people can switch between different tasks? How do visual scan strategies of expert pilots differ from those of novice pilots? | Goal: To understand how design types or elements impact the user experience. Sample research questions: Which layout for an online form is most efficient? How do people view search results pages? Do icon labels improve user performance? |
| Productspecific (atheoretical and doesn’t generalize beyond one product) | User Research Goal: To learn more about the needs, preferences, motivations, and processes of the users or potential users of a particular product. Sample research questions: What are the current practices and preferences of patients learning to use a selfinjection device? Why do users of a particular mobile phone go to the customer support website and does the site meet their needs? |
Design Evaluation
Goal: To evaluate
|