Читать книгу Eye Tracking the User Experience - Aga Bojko - Страница 17

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.