@article{LaubrockCajarEngbert2013,
  author    = {Laubrock, Jochen and Cajar, Anke and Engbert, Ralf},
  title     = {Control of fixation duration during scene viewing by interaction of foveal and peripheral processing},
  series = {Journal of vision},
  volume    = {13},
  journal   = {Journal of vision},
  number    = {12},
  publisher = {Association for Research in Vision and Opthalmology},
  address   = {Rockville},
  issn      = {1534-7362},
  doi       = {10.1167/13.12.11},
  pages     = {20},
  year      = {2013},
  abstract  = {Processing in our visual system is functionally segregated, with the fovea specialized in processing fine detail (high spatial frequencies) for object identification, and the periphery in processing coarse information (low frequencies) for spatial orienting and saccade target selection. Here we investigate the consequences of this functional segregation for the control of fixation durations during scene viewing. Using gaze-contingent displays, we applied high-pass or low-pass filters to either the central or the peripheral visual field and compared eye-movement patterns with an unfiltered control condition. In contrast with predictions from functional segregation, fixation durations were unaffected when the critical information for vision was strongly attenuated (foveal low-pass and peripheral high-pass filtering); fixation durations increased, however, when useful information was left mostly intact by the filter (foveal high-pass and peripheral low-pass filtering). These patterns of results are difficult to explain under the assumption that fixation durations are controlled by foveal processing difficulty. As an alternative explanation, we developed the hypothesis that the interaction of foveal and peripheral processing controls fixation duration. To investigate the viability of this explanation, we implemented a computational model with two compartments, approximating spatial aspects of processing by foveal and peripheral activations that change according to a small set of dynamical rules. The model reproduced distributions of fixation durations from all experimental conditions by variation of few parameters that were affected by specific filtering conditions.},
  language  = {en}
}
@misc{CajarSchneeweissEngelbertetal.2016,
  author    = {Cajar, Anke and Schneeweiß, Paul and Engelbert, Ralf and Laubrock, Jochen},
  title     = {Coupling of attention and saccades when viewing scenes with central and peripheral degradation},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-394918},
  pages     = {19},
  year      = {2016},
  abstract  = {Degrading real-world scenes in the central or the peripheral visual field yields a characteristic pattern: Mean saccade amplitudes increase with central and decrease with peripheral degradation. Does this pattern reflect corresponding modulations of selective attention? If so, the observed saccade amplitude pattern should reflect more focused attention in the central region with peripheral degradation and an attentional bias toward the periphery with central degradation. To investigate this hypothesis, we measured the detectability of peripheral (Experiment 1) or central targets (Experiment 2) during scene viewing when low or high spatial frequencies were gaze-contingently filtered in the central or the peripheral visual field. Relative to an unfiltered control condition, peripheral filtering induced a decrease of the detection probability for peripheral but not for central targets (tunnel vision). Central filtering decreased the detectability of central but not of peripheral targets. Additional post hoc analyses are compatible with the interpretation that saccade amplitudes and direction are computed in partial independence. Our experimental results indicate that task-induced modulations of saccade amplitudes reflect attentional modulations.},
  language  = {en}
}
@article{CajarSchneeweissEngbertetal.2016,
  author    = {Cajar, Anke and Schneeweiß, Paul and Engbert, Ralf and Laubrock, Jochen},
  title     = {Coupling of attention and saccades when viewing scenes with central and peripheral degradation},
  series = {Journal of Vision},
  volume    = {16},
  journal   = {Journal of Vision},
  number    = {2},
  publisher = {ARVO},
  address   = {Rockville, Md.},
  issn      = {1534-7362},
  doi       = {10.1167/16.2.8},
  pages     = {1 -- 19},
  year      = {2016},
  abstract  = {Degrading real-world scenes in the central or the peripheral visual field yields a characteristic pattern: Mean saccade amplitudes increase with central and decrease with peripheral degradation. Does this pattern reflect corresponding modulations of selective attention? If so, the observed saccade amplitude pattern should reflect more focused attention in the central region with peripheral degradation and an attentional bias toward the periphery with central degradation. To investigate this hypothesis, we measured the detectability of peripheral (Experiment 1) or central targets (Experiment 2) during scene viewing when low or high spatial frequencies were gaze-contingently filtered in the central or the peripheral visual field. Relative to an unfiltered control condition, peripheral filtering induced a decrease of the detection probability for peripheral but not for central targets (tunnel vision). Central filtering decreased the detectability of central but not of peripheral targets. Additional post hoc analyses are compatible with the interpretation that saccade amplitudes and direction are computed in partial independence. Our experimental results indicate that task-induced modulations of saccade amplitudes reflect attentional modulations.},
  language  = {en}
}
@article{CajarSchneeweissEngbertetal.2016,
  author    = {Cajar, Anke and Schneeweiss, Paul and Engbert, Ralf and Laubrock, Jochen},
  title     = {Coupling of attention and saccades when viewing scenes with central and peripheral degradation},
  series = {Journal of vision},
  volume    = {16},
  journal   = {Journal of vision},
  publisher = {Association for Research in Vision and Opthalmology},
  address   = {Rockville},
  issn      = {1534-7362},
  doi       = {10.1167/16.2.8},
  pages     = {19},
  year      = {2016},
  abstract  = {Degrading real-world scenes in the central or the peripheral visual field yields a characteristic pattern: Mean saccade amplitudes increase with central and decrease with peripheral degradation. Does this pattern reflect corresponding modulations of selective attention? If so, the observed saccade amplitude pattern should reflect more focused attention in the central region with peripheral degradation and an attentional bias toward the periphery with central degradation. To investigate this hypothesis, we measured the detectability of peripheral (Experiment 1) or central targets (Experiment 2) during scene viewing when low or high spatial frequencies were gaze-contingently filtered in the central or the peripheral visual field. Relative to an unfiltered control condition, peripheral filtering induced a decrease of the detection probability for peripheral but not for central targets (tunnel vision). Central filtering decreased the detectability of central but not of peripheral targets. Additional post hoc analyses are compatible with the interpretation that saccade amplitudes and direction are computed in partial independence. Our experimental results indicate that task-induced modulations of saccade amplitudes reflect attentional modulations.},
  language  = {en}
}
@misc{CajarEngbertLaubrock2016,
  author    = {Cajar, Anke and Engbert, Ralf and Laubrock, Jochen},
  title     = {Eye movements during gaze-contingent spatial-frequency filtering of real-world scenes: Effects of filter location, cutoff, and size},
  series = {Perception},
  volume    = {45},
  journal   = {Perception},
  publisher = {Sage Publ.},
  address   = {London},
  issn      = {0301-0066},
  pages     = {126 -- 126},
  year      = {2016},
  language  = {en}
}
@phdthesis{Cajar2016,
  author    = {Cajar, Anke},
  title     = {Eye-movement control during scene viewing},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-395536},
  school      = {Universit{\"a}t Potsdam},
  pages     = {vii, 133},
  year      = {2016},
  abstract  = {Eye movements serve as a window into ongoing visual-cognitive processes and can thus be used to investigate how people perceive real-world scenes. A key issue for understanding eye-movement control during scene viewing is the roles of central and peripheral vision, which process information differently and are therefore specialized for different tasks (object identification and peripheral target selection respectively). Yet, rather little is known about the contributions of central and peripheral processing to gaze control and how they are coordinated within a fixation during scene viewing. Additionally, the factors determining fixation durations have long been neglected, as scene perception research has mainly been focused on the factors determining fixation locations. The present thesis aimed at increasing the knowledge on how central and peripheral vision contribute to spatial and, in particular, to temporal aspects of eye-movement control during scene viewing. In a series of five experiments, we varied processing difficulty in the central or the peripheral visual field by attenuating selective parts of the spatial-frequency spectrum within these regions. Furthermore, we developed a computational model on how foveal and peripheral processing might be coordinated for the control of fixation duration. The thesis provides three main findings. First, the experiments indicate that increasing processing demands in central or peripheral vision do not necessarily prolong fixation durations; instead, stimulus-independent timing is adapted when processing becomes too difficult. Second, peripheral vision seems to play a prominent role in the control of fixation durations, a notion also implemented in the computational model. The model assumes that foveal and peripheral processing proceed largely in parallel and independently during fixation, but can interact to modulate fixation duration. Thus, we propose that the variation in fixation durations can in part be accounted for by the interaction between central and peripheral processing. Third, the experiments indicate that saccadic behavior largely adapts to processing demands, with a bias of avoiding spatial-frequency filtered scene regions as saccade targets. We demonstrate that the observed saccade amplitude patterns reflect corresponding modulations of visual attention. The present work highlights the individual contributions and the interplay of central and peripheral vision for gaze control during scene viewing, particularly for the control of fixation duration. Our results entail new implications for computational models and for experimental research on scene perception.},
  language  = {en}
}
@misc{LaubrockEngbertCajar2017,
  author    = {Laubrock, Jochen and Engbert, Ralf and Cajar, Anke},
  title     = {Gaze-contingent manipulation of the FVF demonstrates the importance of fixation duration for explaining search behavior},
  series = {Behavioral and brain sciences : an international journal of current research and theory with open peer commentary},
  volume    = {40},
  journal   = {Behavioral and brain sciences : an international journal of current research and theory with open peer commentary},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {0140-525X},
  doi       = {10.1017/S0140525X16000145},
  pages     = {31 -- 32},
  year      = {2017},
  abstract  = {Hulleman \& Olivers' (H\&O's) model introduces variation of the functional visual field (FVF) for explaining visual search behavior. Our research shows how the FVF can be studied using gaze-contingent displays and how FVF variation can be implemented in models of gaze control. Contrary to H\&O, we believe that fixation duration is an important factor when modeling visual search behavior.},
  language  = {en}
}
@article{CajarEngbertLaubrock2020,
  author    = {Cajar, Anke and Engbert, Ralf and Laubrock, Jochen},
  title     = {How spatial frequencies and color drive object search in real-world scenes},
  series = {Journal of vision},
  volume    = {20},
  journal   = {Journal of vision},
  number    = {7},
  publisher = {Association for Research in Vision and Opthalmology},
  address   = {Rockville},
  issn      = {1534-7362},
  doi       = {10.1167/jov.20.7.8},
  pages     = {16},
  year      = {2020},
  abstract  = {When studying how people search for objects in scenes, the inhomogeneity of the visual field is often ignored. Due to physiological limitations, peripheral vision is blurred and mainly uses coarse-grained information (i.e., low spatial frequencies) for selecting saccade targets, whereas high-acuity central vision uses fine-grained information (i.e., high spatial frequencies) for analysis of details. Here we investigated how spatial frequencies and color affect object search in real-world scenes. Using gaze-contingent filters, we attenuated high or low frequencies in central or peripheral vision while viewers searched color or grayscale scenes. Results showed that peripheral filters and central high-pass filters hardly affected search accuracy, whereas accuracy dropped drastically with central low-pass filters. Peripheral filtering increased the time to localize the target by decreasing saccade amplitudes and increasing number and duration of fixations. The use of coarse-grained information in the periphery was limited to color scenes. Central filtering increased the time to verify target identity instead, especially with low-pass filters. We conclude that peripheral vision is critical for object localization and central vision is critical for object identification. Visual guidance during peripheral object localization is dominated by low-frequency color information, whereas high-frequency information, relatively independent of color, is most important for object identification in central vision.},
  language  = {en}
}
@inproceedings{LaubrockCajarEngbert2012,
  author    = {Laubrock, Jochen and Cajar, Anke and Engbert, Ralf},
  title     = {Peripheral spatial frequency processing affects timing and metrics of saccades},
  series = {Perception},
  volume    = {41},
  booktitle = {Perception},
  publisher = {Sage Publ.},
  address   = {London},
  issn      = {0301-0066},
  pages     = {170 -- 170},
  year      = {2012},
  language  = {en}
}
@misc{CajarEngbertLaubrock2022,
  author    = {Cajar, Anke and Engbert, Ralf and Laubrock, Jochen},
  title     = {Potsdam Eye-Movement Corpus for Scene Memorization and Search With Color and Spatial-Frequency Filtering},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Humanwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Humanwissenschaftliche Reihe},
  publisher = {Universit{\"a}tsverlag Potsdam},
  address   = {Potsdam},
  issn      = {1866-8364},
  doi       = {10.25932/publishup-56318},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-563184},
  pages     = {1 -- 7},
  year      = {2022},
  language  = {en}
}