Eye tracking analysis is based on the important assumption that there is a relationship between fixations, our gaze and what we are thinking about. However, there are a few factors that need to be considered for this assumption to be true which will be discussed in this section.
First, sometimes fixations do not necessarily translate into a conscious cognitive process. For example, during a search task one can easily fixate briefly on the search object and miss its presence, especially if the object has an unexpected shape or size (commonly called change blindness). This happens because our expectation of what the object (or scene) should look like modulates our visual attention and interferes with the object detection. This effect can be eliminated from a test if you give clear instructions to the participant, and/or follow up the eye tracking test with an interview to assess the participant’s motivations or expectations.
Second, fixations can be interpreted in different ways depending on the context and objective of the study. For example, if you instruct a participant to freely browse a website (encoding task), a higher number of fixations on an area of the webpage may indicate that the participant is interested in that area (e.g. a photograph or a headline) or that the target area is complex and hard to encode. However, if you give the participant a specific search task (e.g. buy a book on Amazon), a higher number of fixations are often indicative of confusion and uncertainty in recognizing the elements necessary to complete the task. Again, a clear understanding of the objective of the study and careful planning of the tests are important for the interpretation of the eye tracking results.
And third, during the processing of a visual scene, individuals will move their eyes to relevant features in that scene. Some of these features are primarily detected by the peripheral area of our visual field. Due to the low acuity, a feature located in this area will lack shape or color detail but we are still able to use it to recognize well‐known structures and forms as well as make quick, general shape comparisons. As a result, we are able to use the peripheral vision to filter features according to their relevance to us, for example, if we generally avoid advertisement banners on webpages, we might also avoid moving our eyes to other sections of the webpage that have a similar shape simply due to the fact that our peripheral vision “tells” us that they might be banners. The current eye tracker technology will only show the areas on the visual scene that the test subject has been fixating at and the jumps between them (i.e. not the whole visual field). Thus, to fully understand why a test person has been fixating on some areas and ignoring others, it is important that the tests should be accompanied by some form of interview or think‐aloud protocols.
