“The Ketchup Bottle Problem”
In their “How to Conduct Eye Tracking Studies” report, usability experts Kara Pernice and Jakob Nielsen suggest such studies can help reveal:
… the time a person spends on a page, the action he takes there, what he reads aloud, what he hovers the mouse
over, whether he smiles or grimaces, and what he comments on.”
Pernice and Nielsen spend the rest of that report describing how to best conduct such studies, as the title would suggest, and they do so thoroughly starting with participant recruitment.
That may be all one needs to know before starting his or her own eye tracking study — they gave you the reasons to do it and explained how to get it done. However, questions remain including how they’re so sure there is anything to measure in the first place. I found their answer to this question in Chapter 1 of Pernice and Nielsen’s “Eyetracking Web Usability” book. They call it the “mind-eye hypothesis” and describe it as follows:
Knowing where people look would be worthless if it didn’t tell us something about their behavior. Fortunately, it does, thanks to the mind–eye hypothesis, which holds that what people are looking at and what they are thinking about tends to be the same.
If taken to the extreme, the mind–eye hypothesis may seem ludicrous. Looking at and thinking about are certainly not always intertwined. You can think about pink elephants without looking at one. And your thoughts may be on freshly deep-fried donuts while you’re sitting in your car when the stoplight changes. You may not be paying attention to whatever happens to be within your foveal vision, such as the light turning green, until a honk from the car behind you wakes you from your donut dream.
According to the mind–eye hypothesis, people are usually thinking about what they are looking at. They do not always totally understand or engage with it, but if they are looking, they are usually paying attention, especially when concentrating on a particular task.
This makes sense in the world of websites and any digital interface. If an item on a page is clearly visible to a user, and the user is obviously looking right at it, then what could explain why the user does not find it and interact with the item? Where is the user looking? Why? If we can follow this user’s eyes, then we may start to understand how to answer these questions and ultimately how to optimize the website to better serve that item to the user.
As an everyday example — not a digital life example — of this “dilemma,” if you will, Nicholas Gould and Jesse Zolna shared the “Ketchup Bottle Problem” in their article titled “Eye Tracking and Web Usability: A Good Fit?“:
… consider a person staring into an open refrigerator searching for the ketchup. They may be staring directly at the bottle yet, for a variety of potential reasons, might not be paying sufficient attention to it to realize that it’s there at all. Eye tracking would tell us that this person “saw” the ketchup even though they might personally report that no ketchup was present. The risk of this scenario is that eye tracking could erroneously conclude that the user was “successful” in their task of finding the ketchup when they clearly were not.
However, when combined with other data points, this apparent risk can be converted into an opportunity to derive a potentially important observation. Specifically: does the user fixate on the ketchup but not take it out of the refrigerator, or self-report that they didn’t see it? This would indicate that, in fact, they did not “see” the bottle despite its prominent location. This, in turn, would suggest that researchers need to ask what other factors could be at play that prevent the bottle from attracting attention or comprehension (e.g., the bottle is opaque, uses an unfamiliar label design, etc.).
The benefits of eye tracking are clear — you will be able to measure:
- Time on page
- User behavior on page
- User’s vocal behavior during a task
- Where the mouse is placed
- User’s facial expressions
And there’s even more to this, according to Pernice and Nielsen (from Chapter 1 of “Eyetracking Web Usability”:
Eyetrackers as Input Devices
Finally, eyetrackers can go beyond testing to become part of the user interface itself. If the computer knows where the user is looking, the software can adjust the display to present more information about the things the user cares about most. As a simple example, if a user was staring intently at a thumbnail photo on an e-commerce site, the site could automatically display a bigger version of the photo instead of waiting for the user to click a zoom button.
Yes, that means computers can get smarter by tracking a user’s eyes. Very exciting, indeed.
Of course, there are drawbacks and roadblocks to all of this, primarily the cost of conducting such tests. The tools of the eye tracking trade do not come cheaply, relatively speaking, nor are such tools readily available to the average usability and UX teams. But that is an ongoing debate.
The bottom line is: If the data is steady, reliable and clear, then the test is worth it. I believe it is important to place an emphasis on making eye tracking technology more affordable and available to usability practitioners. The benefits are apparent.
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