Abstracts

Eye movements serve as a window intoongoing visual-cognitive processes and can thus be used toinvestigate how people perceive real-world scenes. A key issue forunderstanding eye-movement control during scene viewing is theroles of central and peripheral vision, which process informationdifferently and are therefore specialized for different tasks(object identification and peripheral target selectionrespectively). Yet, rather little is known about the contributionsof central and peripheral processing to gaze control and how theyare coordinated within a fixation during scene viewing.Additionally, the factors determining fixation durations have longbeen neglected, as scene perception research has mainly beenfocused on the factors determining fixation locations. The presentthesis aimed at increasing the knowledge on how central andperipheral vision contribute to spatial and, in particular, totemporal aspects of eye-movement control during scene viewing. In aseries of five experiments, we varied processing difficulty in thecentral or the peripheral visual field by attenuating selectiveparts of the spatial-frequency spectrum within these regions.Furthermore, we developed a computational model on how foveal andperipheral processing might be coordinated for the control offixation duration. The thesis provides three main findings. First,the experiments indicate that increasing processing demands incentral or peripheral vision do not necessarily prolong fixationdurations; instead, stimulus-independent timing is adapted whenprocessing becomes too difficult. Second, peripheral vision seemsto play a prominent role in the control of fixation durations, anotion also implemented in the computational model. The modelassumes that foveal and peripheral processing proceed largely inparallel and independently during fixation, but can interact tomodulate fixation duration. Thus, we propose that the variation infixation durations can in part be accounted for by the interactionbetween central and peripheral processing. Third, the experimentsindicate that saccadic behavior largely adapts to processingdemands, with a bias of avoiding spatial-frequency filtered sceneregions as saccade targets. We demonstrate that the observedsaccade amplitude patterns reflect corresponding modulations ofvisual attention. The present work highlights the individualcontributions and the interplay of central and peripheral visionfor gaze control during scene viewing, particularly for the controlof fixation duration. Our results entail new implications forcomputational models and for experimental research on sceneperception. Blickbewegungen stellen ein Fensterin aktuelle visuell-kognitive Prozesse dar und knnen genutztwerden um zu untersuchen wie Menschen natrliche Szenen wahrnehmen.Eine zentrale Frage ist, welche Rollen zentrales und peripheresSehen fr die Blicksteuerung in Szenen spielen, da sie Informationunterschiedlich verarbeiten und auf verschiedene Aufgabenspezialisiert sind (Objektidentifikation bzw.Advisors/Committee Members: Engbert, Ralf (advisor), Laubrock, Jochen (advisor).