@phdthesis{Rothkegel2018,
  author    = {Rothkegel, Lars Oliver Martin},
  title     = {Human scanpaths in natural scene viewing and natural scene search},
  doi       = {10.25932/publishup-42000},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-420005},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xv, 131},
  year      = {2018},
  abstract  = {Understanding how humans move their eyes is an important part for understanding the functioning of the visual system. Analyzing eye movements from observations of natural scenes on a computer screen is a step to understand human visual behavior in the real world. When analyzing eye-movement data from scene-viewing experiments, the impor- tant questions are where (fixation locations), how long (fixation durations) and when (ordering of fixations) participants fixate on an image. By answering these questions, computational models can be developed which predict human scanpaths. Models serve as a tool to understand the underlying cognitive processes while observing an image, especially the allocation of visual attention. The goal of this thesis is to provide new contributions to characterize and model human scanpaths on natural scenes. The results from this thesis will help to understand and describe certain systematic eye-movement tendencies, which are mostly independent of the image. One eye-movement tendency I focus on throughout this thesis is the tendency to fixate more in the center of an image than on the outer parts, called the central fixation bias. Another tendency, which I will investigate thoroughly, is the characteristic distribution of angles between successive eye movements. The results serve to evaluate and improve a previously published model of scanpath generation from our laboratory, the SceneWalk model. Overall, six experiments were conducted for this thesis which led to the following five core results: i) A spatial inhibition of return can be found in scene-viewing data. This means that locations which have already been fixated are afterwards avoided for a certain time interval (Chapter 2). ii) The initial fixation position when observing an image has a long-lasting influence of up to five seconds on further scanpath progression (Chapter 2 \& 3). iii) The often described central fixation bias on images depends strongly on the duration of the initial fixation. Long-lasting initial fixations lead to a weaker central fixation bias than short fixations (Chapter 2 \& 3). iv) Human observers adjust their basic eye-movement parameters, like fixation dura- tions and saccade amplitudes, to the visual properties of a target they look for in visual search (Chapter 4). v) The angle between two adjacent saccades is an indicator for the selectivity of the upcoming saccade target (Chapter 4). All results emphasize the importance of systematic behavioral eye-movement tenden- cies and dynamic aspects of human scanpaths in scene viewing.},
  language  = {en}
}
@article{KlieglWeiDambacheretal.2011,
  author    = {Kliegl, Reinhold and Wei, Ping and Dambacher, Michael and Yan, Ming and Zhou, Xiaolin},
  title     = {Experimental effects and individual differences in linear mixed models estimating the relationship between spatial, object, and attraction effects in visual attention},
  series = {Frontiers in psychology},
  volume    = {2},
  journal   = {Frontiers in psychology},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {1664-1078},
  doi       = {10.3389/fpsyg.2010.00238},
  pages     = {12},
  year      = {2011},
  abstract  = {Linear mixed models (LMMs) provide a still underused methodological perspective on combining experimental and individual-differences research. Here we illustrate this approach with two-rectangle cueing in visual attention (Egly et al., 1994). We replicated previous experimental cue-validity effects relating to a spatial shift of attention within an object (spatial effect), to attention switch between objects (object effect), and to the attraction of attention toward the display centroid (attraction effect), also taking into account the design-inherent imbalance of valid and other trials. We simultaneously estimated variance/covariance components of subject-related random effects for these spatial, object, and attraction effects in addition to their mean reaction times (RTs). The spatial effect showed a strong positive correlation with mean RT and a strong negative correlation with the attraction effect. The analysis of individual differences suggests that slow subjects engage attention more strongly at the cued location than fast subjects. We compare this joint LMM analysis of experimental effects and associated subject-related variances and correlations with two frequently used alternative statistical procedures.},
  language  = {en}
}
@misc{KlieglWeiDambacheretal.2011,
  author    = {Kliegl, Reinhold and Wei, Ping and Dambacher, Michael and Yan, Ming and Zhou, Xiaolin},
  title     = {Experimental effects and individual differences in linear mixed models: Estimating the relationship between spatial, object, and attraction effects in visual attention},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-56859},
  year      = {2011},
  abstract  = {Linear mixed models (LMMs) provide a still underused methodological perspective on combining experimental and individual-differences research. Here we illustrate this approach with two-rectangle cueing in visual attention (Egly et al., 1994). We replicated previous experimental cue-validity effects relating to a spatial shift of attention within an object (spatial effect), to attention switch between objects (object effect), and to the attraction of attention toward the display centroid (attraction effect), also taking into account the design-inherent imbalance of valid and other trials. We simultaneously estimated variance/covariance components of subject-related random effects for these spatial, object, and attraction effects in addition to their mean reaction times (RTs). The spatial effect showed a strong positive correlation with mean RT and a strong negative correlation with the attraction effect. The analysis of individual differences suggests that slow subjects engage attention more strongly at the cued location than fast subjects. We compare this joint LMM analysis of experimental effects and associated subject-related variances and correlations with two frequently used alternative statistical procedures},
  language  = {en}
}