M. Joos

Time course of information processing during scene perception: The relationship between saccade amplitude and fixation duration

The present study focuses on two aspects of the time course of visual information processing during the perception of natural scenes. The first aspect is the change of fixation duration and saccade amplitude during the first couple of seconds of the inspection period, as has been described by Buswell (1935), among others. This common effect suggests that the saccade amplitude and fixation duration are in some way controlled by the same mechanism. A simple exponential model containing two parameters can describe the phenomena quite satisfactorily. The parameters of the model show that saccade amplitude and fixation duration may be controlled by a common mechanism. The second aspect under scrutiny is the apparent lack of correlation between saccade amplitude and fixation duration (Viviani, 1990). The present study shows that a strong but nonlinear relationship between saccade amplitude and fixation duration does exist in picture viewing. A model, based on notions laid out by Findlay and Walkers (1999) model of saccade generation and on the idea of two modes of visual processing (Trevarthen, 1968), was developed to explain this relationship. The model both fits the data quite accurately and can explain a number of related phenomena.

TOWARDS AN EXPRESS-DIAGNOSTICS FOR LEVEL OF PROCESSING AND HAZARD PERCEPTION

Abstract The analysis of eye movements can provide rich information about drivers attention and the course of behaviour in hazardous situations. We present data from a driving simulation study showing that the switching between preattentive and attentive processing is reflected in visual fixations. For this initial analysis, we considered fixations from the perspective of their duration and the amplitude of related saccades. Since fixation durations may change instantaneously from one fixation to the next, we further selected the temporal vicinity of the emerging hazard for a closer analysis of fixations around this time. With this second type of analysis, the fixations that actually “detect” a critical event can be discovered and their duration measured. Upon detection of an immediate hazard, there is an increase in fixation duration and a corresponding increase in occurrence of attentive fixations on the cost of preattentive ones. This switching from one level of processing to another is recognisable on a short, phasic time scale. We finally discuss attentional conditions where overlooked or not sufficiently processed hazards do not lead to the appropriate breaking reaction on the part of the driver.

Gaze controlled games

The quality and availability of eye tracking equipment has been increasing while costs have been decreasing. These trends increase the possibility of using eye trackers for entertainment purposes. Games that can be controlled solely through movement of the eyes would be accessible to persons with decreased limb mobility or control. On the other hand, use of eye tracking can change the gaming experience for all players, by offering richer input and enabling attention-aware games. Eye tracking is not currently widely supported in gaming, and games specifically developed for use with an eye tracker are rare. This paper reviews past work on eye tracker gaming and charts future development possibilities in different sub-domains within. It argues that based on the user input requirements and gaming contexts, conventional computer games can be classified into groups that offer fundamentally different opportunities for eye tracker input. In addition to the inherent design issues, there are challenges and varying levels of support for eye tracker use in the technical implementations of the games.

Change detection and occlusion modes in road-traffic scenarios

Abstract Change blindness phenomena are widely known in cognitive science, but their relation to driving is not quite clear. We report a study where subjects viewed colour video stills of natural traffic while eye movements were recorded. A change could occur randomly in three different occlusion modes—blinks, blanks and saccades—or during a fixation (as control condition). These changes could be either relevant or irrelevant with respect to the traffic safety. We used deletions as well as insertions of objects. All occlusion modes were equivalent concerning detection rate and reaction time, deviating from the control condition only. The detection of relevant changes was both more likely and faster than that of irrelevant ones, particularly for relevant insertions, which approached the base line level. Even in this case, it took about 180 ms longer to react to changes when they occurred during a saccade, blink or blank. In a second study, relevant insertions and the blank occlusion were used in a driving simulator environment. We found a surprising effect in the dynamic setting: an advantage in change detection rate and time with blanks compared to the control condition. Change detection was also good during blinks, but not in saccades. Possible explanation of these effects and their practical implications are discussed.

Evaluation of perception performance in neck dissection planning using eye tracking and attention landscapes

Neck dissection is a surgical intervention at which cervical lymph node metastases are removed. Accurate surgical planning is of high importance because wrong judgment of the situation causes severe harm for the patient. Diagnostic perception of radiological images by a surgeon is an acquired skill that can be enhanced by training and experience. To improve accuracy in detecting pathological lymph nodes by newcomers and less experienced professionals, it is essential to understand how surgical experts solve relevant visual and recognition tasks. By using eye tracking and especially the newly-developed attention landscapes visualizations, it could be determined whether visualization options, for example 3D models instead of CT data, help in increasing accuracy and speed of neck dissection planning. Thirteen ORL surgeons with different levels of expertise participated in this study. They inspected different visualizations of 3D models and original CT datasets of patients. Among others, we used scanpath analysis and attention landscapes to interpret the inspection strategies. It was possible to distinguish different patterns of visual exploratory activity. The experienced surgeons exhibited a higher concentration of attention on the limited number of areas of interest and demonstrated less saccadic eye movements indicating a better orientation.