Effects Of Gaze-Contingent Stimuli On Eye Movements

Although we are mostly unaware of the fact that our eyes move several times per second, the way we perceive the world depends to a large extent on the exact scan paths our eyes describe. Indeed, recent studies have impressively shown that even substantial changes to a visual display can go unnoticed if the observer’s attention is directed somewhere else. Therefore, one of the goals of the Information technology for active perception (Itap) project is to improve communication systems by guiding the scan path of an observer. In this thesis, a system was implemented that allows to perform first experiments towards this goal. This system consists of a workstation that is connected to an eye-tracking device. High resolution movies can be displayed and manipulated in real time. The manipulation depends on the structure of the image sequence and on the gaze of the observer. To reduce the overall latency was a major design goal so that the system is capable of reacting to an eye movement within less than 30 ms. Results will be presented for experiments where image sequence manipulations were designed to attract the gaze of an observer. One of these manipulations was the sudden onset of a red square, the other stimulus type simulated the optical flow of an object moving towards the observer. The results show that it is possible to influence the gaze of an observer, but the strength of this effect seems to depend on the underlying image sequence.