The 1980s also saw the birth of using eye-tracking to answer questions related to human-computer interaction. If covert attention is common during eye-tracking recordings, the resulting scan-path and fixation patterns would often show not where our attention has been, but only where the eye has been looking, failing to indicate cognitive processing. However, gaze-contingent techniques offer an interesting option in order to disentangle overt and covert attentions, to differentiate what is fixated and what is processed.ĭuring the 1980s, the eye-mind hypothesis was often questioned in light of covert attention, the attention to something that one is not looking at, which people often do. The hypothesis is often taken for granted by researchers using eye-tracking. If this hypothesis is correct, then when a subject looks at a word or object, he or she also thinks about it (process cognitively), and for exactly as long as the recorded fixation. In 1980, Just and Carpenter formulated the influential Strong eye-mind hypothesis, that "there is no appreciable lag between what is fixated and what is processed". A good overview of the research in this period is given by Rayner. In the 1970s, eye-tracking research expanded rapidly, particularly reading research. This study by Hunziker (1970) on eye tracking in problem solving used simple 8 mm film to track eye movement by filming the subject through a glass plate on which the visual problem was displayed. Additional time spent on perception is not used to examine the secondary elements, but to reexamine the most important elements." when changing its points of fixation, the observer's eye repeatedly returns to the same elements of the picture. Often an observer will focus his attention on elements that are unusual in the particular circumstances, unfamiliar, incomprehensible, and so on." ". 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. 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). "Records of eye movements show that the observer's attention is usually held only by certain elements of the picture. This study by Yarbus (1967) harvtxt error: no target: CITEREFYarbus1967 ( help) is often referred to as evidence on how the task given to a person influences his or her eye movement. 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 on not only what is shown on the picture, but also the problem facing the observer and the information that he hopes to gain from the picture."
He also wrote about the relation between fixations and interest: He showed that the task given to a subject has a very large influence on the subject's eye movement. Yarbus performed eye tracking research, and his 1967 book is often quoted. Buswell made systematic studies into reading and picture viewing.
The first non-intrusive eye-trackers were built by Guy Thomas Buswell in Chicago, using beams of light that were reflected on the eye, then recording on film. Huey studied and quantified regressions (only a small proportion of saccades are regressions), and he showed that some words in a sentence are not fixated. The lens was connected to an aluminum pointer that moved in response to the movement of the eye. The eyes never move smoothly over still text.Įdmund Huey built an early eye tracker, using a sort of contact lens with a hole for the pupil.
This is the typical pattern of eye movement during reading. This observation raised important questions about reading, questions which were explored during the 1900s: On which words do the eyes stop? For how long? When do they regress to already seen words?Īn example of fixations and saccades over text.
EYE TRACKING VIDEO SERIES
For example, Louis Émile Javal observed in 1879 that reading does not involve a smooth sweeping of the eyes along the text, as previously assumed, but a series of short stops (called fixations) and quick saccades. In the 1800s, studies of eye movement were made using direct observations. 6.2 Eye-tracking of younger and elderly people while walking.6.1 Eye-tracking while driving a car in a difficult situation.