TY - JOUR A1 - Hohenstein, Sven A1 - Matuschek, Hannes A1 - Kliegl, Reinhold T1 - Linked linear mixed models: A joint analysis of fixation locations and fixation durations in natural reading JF - Psychonomic bulletin & review : a journal of the Psychonomic Society N2 - The complexity of eye-movement control during reading allows measurement of many dependent variables, the most prominent ones being fixation durations and their locations in words. In current practice, either variable may serve as dependent variable or covariate for the other in linear mixed models (LMMs) featuring also psycholinguistic covariates of word recognition and sentence comprehension. Rather than analyzing fixation location and duration with separate LMMs, we propose linking the two according to their sequential dependency. Specifically, we include predicted fixation location (estimated in the first LMM from psycholinguistic covariates) and its associated residual fixation location as covariates in the second, fixation-duration LMM. This linked LMM affords a distinction between direct and indirect effects (mediated through fixation location) of psycholinguistic covariates on fixation durations. Results confirm the robustness of distributed processing in the perceptual span. They also offer a resolution of the paradox of the inverted optimal viewing position (IOVP) effect (i.e., longer fixation durations in the center than at the beginning and end of words) although the opposite (i.e., an OVP effect) is predicted from default assumptions of psycholinguistic processing efficiency: The IOVP effect in fixation durations is due to the residual fixation-location covariate, presumably driven primarily by saccadic error, and the OVP effect (at least the left part of it) is uncovered with the predicted fixation-location covariate, capturing the indirect effects of psycholinguistic covariates. We expect that linked LMMs will be useful for the analysis of other dynamically related multiple outcomes, a conundrum of most psychonomic research. KW - Linear mixed model KW - Model linkage KW - Eye movements KW - Reading Y1 - 2017 U6 - https://doi.org/10.3758/s13423-016-1138-y SN - 1069-9384 SN - 1531-5320 VL - 24 SP - 637 EP - 651 PB - Springer CY - New York ER - TY - JOUR A1 - Trukenbrod, Hans Arne A1 - Engbert, Ralf T1 - ICAT: a computational model for the adaptive control of fixation durations JF - Psychonomic bulletin & review : a journal of the Psychonomic Society N2 - Eye movements depend on cognitive processes related to visual information processing. Much has been learned about the spatial selection of fixation locations, while the principles governing the temporal control (fixation durations) are less clear. Here, we review current theories for the control of fixation durations in tasks like visual search, scanning, scene perception, and reading and propose a new model for the control of fixation durations. We distinguish two local principles from one global principle of control. First, an autonomous saccade timer initiates saccades after random time intervals (local-I). Second, foveal inhibition permits immediate prolongation of fixation durations by ongoing processing (local-II). Third, saccade timing is adaptive, so that the mean timer value depends on task requirements and fixation history (Global). We demonstrate by numerical simulations that our model qualitatively reproduces patterns of mean fixation durations and fixation duration distributions observed in typical experiments. When combined with assumptions of saccade target selection and oculomotor control, the model accounts for both temporal and spatial aspects of eye movement control in two versions of a visual search task. We conclude that the model provides a promising framework for the control of fixation durations in saccadic tasks. KW - Computational modeling KW - Eye movements KW - Adaptive control KW - Fixation duration Y1 - 2014 U6 - https://doi.org/10.3758/s13423-013-0575-0 SN - 1069-9384 SN - 1531-5320 VL - 21 IS - 4 SP - 907 EP - 934 PB - Springer CY - New York ER -