TY - GEN A1 - Backhaus, Daniel A1 - Engbert, Ralf A1 - Rothkegel, Lars Oliver Martin A1 - Trukenbrod, Hans Arne T1 - Task-dependence in scene perception: Head unrestrained viewing using mobile eye-tracking T2 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe N2 - Real-world scene perception is typically studied in the laboratory using static picture viewing with restrained head position. Consequently, the transfer of results obtained in this paradigm to real-word scenarios has been questioned. The advancement of mobile eye-trackers and the progress in image processing, however, permit a more natural experimental setup that, at the same time, maintains the high experimental control from the standard laboratory setting. We investigated eye movements while participants were standing in front of a projector screen and explored images under four specific task instructions. Eye movements were recorded with a mobile eye-tracking device and raw gaze data were transformed from head-centered into image-centered coordinates. We observed differences between tasks in temporal and spatial eye-movement parameters and found that the bias to fixate images near the center differed between tasks. Our results demonstrate that current mobile eye-tracking technology and a highly controlled design support the study of fine-scaled task dependencies in an experimental setting that permits more natural viewing behavior than the static picture viewing paradigm. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 871 KW - scene viewing KW - real-world scenarios KW - mobile eye-tracking KW - task influence KW - central fixation bias Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-519124 SN - 1866-8364 IS - 5 ER - TY - JOUR A1 - Backhaus, Daniel A1 - Engbert, Ralf A1 - Rothkegel, Lars Oliver Martin A1 - Trukenbrod, Hans Arne T1 - Task-dependence in scene perception: Head unrestrained viewing using mobile eye-tracking JF - Journal of vision N2 - Real-world scene perception is typically studied in the laboratory using static picture viewing with restrained head position. Consequently, the transfer of results obtained in this paradigm to real-word scenarios has been questioned. The advancement of mobile eye-trackers and the progress in image processing, however, permit a more natural experimental setup that, at the same time, maintains the high experimental control from the standard laboratory setting. We investigated eye movements while participants were standing in front of a projector screen and explored images under four specific task instructions. Eye movements were recorded with a mobile eye-tracking device and raw gaze data were transformed from head-centered into image-centered coordinates. We observed differences between tasks in temporal and spatial eye-movement parameters and found that the bias to fixate images near the center differed between tasks. Our results demonstrate that current mobile eye-tracking technology and a highly controlled design support the study of fine-scaled task dependencies in an experimental setting that permits more natural viewing behavior than the static picture viewing paradigm. KW - scene viewing KW - real-world scenarios KW - mobile eye-tracking KW - task KW - influence KW - central fixation bias Y1 - 2020 U6 - https://doi.org/10.1167/jov.20.5.3 SN - 1534-7362 VL - 20 IS - 5 SP - 1 EP - 21 PB - Association for Research in Vision and Opthalmology CY - Rockville ER - TY - JOUR A1 - Cajar, Anke A1 - Engbert, Ralf A1 - Laubrock, Jochen T1 - How spatial frequencies and color drive object search in real-world scenes BT - a new eye-movement corpus JF - Journal of vision N2 - 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. KW - scene viewing KW - eye movements KW - object search KW - central and peripheral KW - vision KW - spatial frequencies KW - color KW - gaze-contingent displays Y1 - 2020 U6 - https://doi.org/10.1167/jov.20.7.8 SN - 1534-7362 VL - 20 IS - 7 PB - Association for Research in Vision and Opthalmology CY - Rockville ER - TY - JOUR A1 - Chandra, Johan A1 - Krügel, André A1 - Engbert, Ralf T1 - Modulation of oculomotor control during reading of mirrored and inverted texts JF - Scientific Reports N2 - The interplay between cognitive and oculomotor processes during reading can be explored when the spatial layout of text deviates from the typical display. In this study, we investigate various eye-movement measures during reading of text with experimentally manipulated layout (word-wise and letter-wise mirrored-reversed text as well as inverted and scrambled text). While typical findings (e.g., longer mean fixation times, shorter mean saccades lengths) in reading manipulated texts compared to normal texts were reported in earlier work, little is known about changes of oculomotor targeting observed in within-word landing positions under the above text layouts. Here we carry out precise analyses of landing positions and find substantial changes in the so-called launch-site effect in addition to the expected overall slow-down of reading performance. Specifically, during reading of our manipulated text conditions with reversed letter order (against overall reading direction), we find a reduced launch-site effect, while in all other manipulated text conditions, we observe an increased launch-site effect. Our results clearly indicate that the oculomotor system is highly adaptive when confronted with unusual reading conditions. KW - human behaviour KW - psychology KW - eye-movement control KW - e-z reader KW - ideal-observer model KW - fixation locations KW - landing positions KW - saccade generation KW - cognitive-control KW - dynamical model KW - decision-theory KW - attention Y1 - 2019 U6 - https://doi.org/10.1038/s41598-020-60833-6 SN - 2045-2322 VL - 10 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - GEN A1 - Chandra, Johan A1 - Krügel, André A1 - Engbert, Ralf T1 - Modulation of oculomotor control during reading of mirrored and inverted texts T2 - Postprints der Universität Potsdam : Humanwissenschaftliche Reihe N2 - The interplay between cognitive and oculomotor processes during reading can be explored when the spatial layout of text deviates from the typical display. In this study, we investigate various eye-movement measures during reading of text with experimentally manipulated layout (word-wise and letter-wise mirrored-reversed text as well as inverted and scrambled text). While typical findings (e.g., longer mean fixation times, shorter mean saccades lengths) in reading manipulated texts compared to normal texts were reported in earlier work, little is known about changes of oculomotor targeting observed in within-word landing positions under the above text layouts. Here we carry out precise analyses of landing positions and find substantial changes in the so-called launch-site effect in addition to the expected overall slow-down of reading performance. Specifically, during reading of our manipulated text conditions with reversed letter order (against overall reading direction), we find a reduced launch-site effect, while in all other manipulated text conditions, we observe an increased launch-site effect. Our results clearly indicate that the oculomotor system is highly adaptive when confronted with unusual reading conditions. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 659 KW - human behaviour KW - psychology KW - eye-movement control KW - e-z reader KW - ideal-observer model KW - fixation locations KW - landing positions KW - saccade generation KW - cognitive-control KW - dynamical model KW - decision-theory KW - attention Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-494879 SN - 1866-8364 IS - 659 ER - TY - JOUR A1 - Chandra, Johan A1 - Krügel, André A1 - Engbert, Ralf T1 - Experimental test of Bayesian saccade targeting under reversed reading direction JF - Attention, Perception, & Psychophysics N2 - During reading, rapid eye movements (saccades) shift the reader's line of sight from one word to another for high-acuity visual information processing. While experimental data and theoretical models show that readers aim at word centers, the eye-movement (oculomotor) accuracy is low compared to other tasks. As a consequence, distributions of saccadic landing positions indicate large (i) random errors and (ii) systematic over- and undershoot of word centers, which additionally depend on saccade lengths (McConkie et al.Visual Research, 28(10), 1107-1118,1988). Here we show that both error components can be simultaneously reduced by reading texts from right to left in German language (N= 32). We used our experimental data to test a Bayesian model of saccade planning. First, experimental data are consistent with the model. Second, the model makes specific predictions of the effects of the precision of prior and (sensory) likelihood. Our results suggest that it is a more precise sensory likelihood that can explain the reduction of both random and systematic error components. KW - eye movements and reading KW - Bayesian modeling KW - eye-movement control KW - model KW - fixation KW - attention KW - words KW - swift Y1 - 2019 U6 - https://doi.org/10.3758/s13414-019-01814-4 SN - 1943-393X SN - 1943-3921 VL - 82 SP - 1230 EP - 1240 PB - Springer CY - New York, NY ER - TY - JOUR A1 - Krügel, André A1 - Rothkegel, Lars A1 - Engbert, Ralf T1 - No exception from Bayes’ rule BT - the presence and absence of the range effect for saccades explained JF - Journal of vision N2 - In an influential theoretical model, human sensorimotor control is achieved by a Bayesian decision process, which combines noisy sensory information and learned prior knowledge. A ubiquitous signature of prior knowledge and Bayesian integration in human perception and motor behavior is the frequently observed bias toward an average stimulus magnitude (i.e., a central-tendency bias, range effect, regression-to-the-mean effect). However, in the domain of eye movements, there is a recent controversy about the fundamental existence of a range effect in the saccadic system. Here we argue that the problem of the existence of a range effect is linked to the availability of prior knowledge for saccade control. We present results from two prosaccade experiments that both employ an informative prior structure (i.e., a nonuniform Gaussian distribution of saccade target distances). Our results demonstrate the validity of Bayesian integration in saccade control, which generates a range effect in saccades. According to Bayesian integration principles, the saccadic range effect depends on the availability of prior knowledge and varies in size as a function of the reliability of the prior and the sensory likelihood. KW - saccades KW - saccadic accuracy KW - range effect KW - Bayesian sensorimotor KW - integration KW - central-tendency bias Y1 - 2020 U6 - https://doi.org/10.1167/jov.20.7.15 SN - 1534-7362 VL - 20 IS - 7 PB - ARVO CY - Rockville ER - TY - JOUR A1 - Malem-Shinitski, Noa A1 - Opper, Manfred A1 - Reich, Sebastian A1 - Schwetlick, Lisa A1 - Seelig, Stefan A. A1 - Engbert, Ralf T1 - A mathematical model of local and global attention in natural scene viewing JF - PLoS Computational Biology : a new community journal N2 - Author summary
Switching between local and global attention is a general strategy in human information processing. We investigate whether this strategy is a viable approach to model sequences of fixations generated by a human observer in a free viewing task with natural scenes. Variants of the basic model are used to predict the experimental data based on Bayesian inference. Results indicate a high predictive power for both aggregated data and individual differences across observers. The combination of a novel model with state-of-the-art Bayesian methods lends support to our two-state model using local and global internal attention states for controlling eye movements.
Understanding the decision process underlying gaze control is an important question in cognitive neuroscience with applications in diverse fields ranging from psychology to computer vision. The decision for choosing an upcoming saccade target can be framed as a selection process between two states: Should the observer further inspect the information near the current gaze position (local attention) or continue with exploration of other patches of the given scene (global attention)? Here we propose and investigate a mathematical model motivated by switching between these two attentional states during scene viewing. The model is derived from a minimal set of assumptions that generates realistic eye movement behavior. We implemented a Bayesian approach for model parameter inference based on the model's likelihood function. In order to simplify the inference, we applied data augmentation methods that allowed the use of conjugate priors and the construction of an efficient Gibbs sampler. This approach turned out to be numerically efficient and permitted fitting interindividual differences in saccade statistics. Thus, the main contribution of our modeling approach is two-fold; first, we propose a new model for saccade generation in scene viewing. Second, we demonstrate the use of novel methods from Bayesian inference in the field of scan path modeling. Y1 - 2020 U6 - https://doi.org/10.1371/journal.pcbi.1007880 SN - 1553-734X SN - 1553-7358 VL - 16 IS - 12 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Schwetlick, Lisa A1 - Rothkegel, Lars Oliver Martin A1 - Trukenbrod, Hans Arne A1 - Engbert, Ralf T1 - Modeling the effects of perisaccadic attention on gaze statistics during scene viewing JF - Communications biology N2 - Lisa Schwetlick et al. present a computational model linking visual scan path generation in scene viewing to physiological and experimental work on perisaccadic covert attention, the act of attending to an object visually without obviously moving the eyes toward it. They find that integrating covert attention into predictive models of visual scan paths greatly improves the model's agreement with experimental data.
How we perceive a visual scene depends critically on the selection of gaze positions. For this selection process, visual attention is known to play a key role in two ways. First, image-features attract visual attention, a fact that is captured well by time-independent fixation models. Second, millisecond-level attentional dynamics around the time of saccade drives our gaze from one position to the next. These two related research areas on attention are typically perceived as separate, both theoretically and experimentally. Here we link the two research areas by demonstrating that perisaccadic attentional dynamics improve predictions on scan path statistics. In a mathematical model, we integrated perisaccadic covert attention with dynamic scan path generation. Our model reproduces saccade amplitude distributions, angular statistics, intersaccadic turning angles, and their impact on fixation durations as well as inter-individual differences using Bayesian inference. Therefore, our result lend support to the relevance of perisaccadic attention to gaze statistics. KW - Computational models KW - Human behaviour KW - Visual system Y1 - 2020 U6 - https://doi.org/10.1038/s42003-020-01429-8 SN - 2399-3642 VL - 3 IS - 1 PB - Springer Nature CY - London ER - TY - JOUR A1 - Seelig, Stefan A. A1 - Rabe, Maximilian Michael A1 - Malem-Shinitski, Noa A1 - Risse, Sarah A1 - Reich, Sebastian A1 - Engbert, Ralf T1 - Bayesian parameter estimation for the SWIFT model of eye-movement control during reading JF - Journal of mathematical psychology N2 - Process-oriented theories of cognition must be evaluated against time-ordered observations. Here we present a representative example for data assimilation of the SWIFT model, a dynamical model of the control of fixation positions and fixation durations during natural reading of single sentences. First, we develop and test an approximate likelihood function of the model, which is a combination of a spatial, pseudo-marginal likelihood and a temporal likelihood obtained by probability density approximation Second, we implement a Bayesian approach to parameter inference using an adaptive Markov chain Monte Carlo procedure. Our results indicate that model parameters can be estimated reliably for individual subjects. We conclude that approximative Bayesian inference represents a considerable step forward for computational models of eye-movement control, where modeling of individual data on the basis of process-based dynamic models has not been possible so far. KW - dynamical models KW - reading KW - eye movements KW - saccades KW - likelihood function KW - Bayesian inference KW - MCMC KW - interindividual differences Y1 - 2020 U6 - https://doi.org/10.1016/j.jmp.2019.102313 SN - 0022-2496 SN - 1096-0880 VL - 95 PB - Elsevier CY - San Diego ER -