“Eye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head.
In the 1950s, Alfred L. Yarbus did important eye tracking research and his 1967 book is often quoted.
He showed that the task given to a subject has a very large influence on the subject’s eye movement. He also wrote about the relation between fixations and interest:
All the records…show conclusively that the character of the eye movement is either completely independent of or only very slightly dependent on the material of the picture and how it was made, provided that it is flat or nearly flat.
The cyclical pattern in the examination of pictures is dependent not only on what is shown on the picture, but also on the problem facing the observer and the information that he hopes to gain from the picture.Records of eye movements show that the observer’s attention is usually held only by certain elements of the picture…
Eye movement reflects the human thought processes; so the observer’s thought may be followed to some extent from records of eye movement (the thought accompanying the examination of the particular object). It is easy to determine from these records which elements attract the observer’s eye (and, consequently, his thought), in what order, and how often.
The observer’s attention is frequently drawn to elements which do not give important information but which, in his opinion, may do so.
Often an observer will focus his attention on elements that are unusual in the particular circumstances, unfamiliar, incomprehensible, and so on.
…When changing its points of fixation, the observer’s eye repeatedly returns to the same elements of the picture. Additional time spent on perception is not used to examine the secondary elements, but to reexamine the most important elements.”