In visuospatial terms, a saccade is an eye movement from one area in the visual field to another, and usability testing using eye-tracking equipment tracks the timing and progression of saccades across a user interface in response to certain stimuli. These stimuli may include 1) the first presentation of the interface to the user, 2) the modification of the visual field due to animation (Flash, banners, animated GIFs, etc.), 3) the slow download of information to be presented, or any number of other things that can attract your gaze.
Unfortunately, where you are looking is not necessarily where you are paying attention. The spotlight theory of attention states that you can attend to a different section of your visual field than you are currently looking at. This means that even though you are currently looking at this line of text, your attentional spotlight could be on your buddy list to see who just signed on, or down at your Mac OS X dock to notice an application icon bouncing up and down, or even on nothing in particular because you are paying attention to a thought process going on in your head as opposed to what’s happening on the screen. Ever read a passage of a book and then realize after the paragraph is complete that you don’t remember anything you just read? That happened because your visual focus wasn’t in sync with your spotlight of attention, thus your attention wandered and you missed the point of your reading.
User Interfaces and Spotlighting
Users who have no familiarity with the interface presented in front of them will pay more attention to what they are doing than if they are a seasoned user with hours of experience. I no longer look at the keyboard to open a new tab in Safari, I simply position my left thumb and index finger unconsciously and a new tab appears. Did I pay attention to the physical act of moving my fingers in a manner that puts them on top of the correct keys? Did I have to break concentration in order to remember the correct keystroke sequence to make a new tab? Of course not, because it is a learned response which requires no attention in order to perform it correctly.
Difficulties arise when performing usability tests on subjects who are very familiar with their scenario and can breeze right through it based on learned interaction sequences. When you stop attending to the interface you are using and simply go on subconscious learned activities, the usability testing (and eye-tracking) is now biased and altered. The interface’s spatial cues are there to inform the user about possible interaction paths, but when your attentional spotlight is not focused on the task at hand, the interface’s spatial cues are bypassed and you are not interacting with the UI in the manner it was designed. Your familiarity with the interface is effectively blocking positive interaction, thus usability testing needs to be adjusted.
Combatting Learned Interaction
When testing seasoned users is a necessity, think aloud protocol should be used in order to facilitate a full interaction with the interface. By forcing one to speak about their cognitive processes during testing it verifies that they are not using learned interactions. When both talking and doing at the same time, you are increasing the chances that their spotlight of attention is fixed at their gaze point instead of them attending elsewhere. Now that they are focused on the task at hand, they will pay more attention to the user interface in front of them and can turn back into a valuable usability tester.
And Now What?
People sometimes forget that the user experience industry has its base in psychology, and that knowing how information is processed in the brain helps someone become a better user interface designer.