TY  - JOUR
A1  - Risse, Sarah
A1  - Hohenstein, Sven
A1  - Kliegl, Reinhold
A1  - Engbert, Ralf
T1  - A theoretical analysis of the perceptual span based on SWIFT simulations of the n+2 boundary paradigm
JF  - Visual cognition
N2  - Eye-movement experiments suggest that the perceptual span during reading is larger than the fixated word, asymmetric around the fixation position, and shrinks in size contingent on the foveal processing load. We used the SWIFT model of eye-movement control during reading to test these hypotheses and their implications under the assumption of graded parallel processing of all words inside the perceptual span. Specifically, we simulated reading in the boundary paradigm and analysed the effects of denying the model to have valid preview of a parafoveal word n + 2 two words to the right of fixation. Optimizing the model parameters for the valid preview condition only, we obtained span parameters with remarkably realistic estimates conforming to the empirical findings on the size of the perceptual span. More importantly, the SWIFT model generated parafoveal processing up to word n + 2 without fitting the model to such preview effects. Our results suggest that asymmetry and dynamic modulation are plausible properties of the perceptual span in a parallel word-processing model such as SWIFT. Moreover, they seem to guide the flexible distribution of processing resources during reading between foveal and parafoveal words.
KW  - Eye movements
KW  - Reading
KW  - Computational modelling
KW  - Perceptual span
KW  - Preview
Y1  - 2014
U6  - https://doi.org/10.1080/13506285.2014.881444
SN  - 1350-6285
SN  - 1464-0716
VL  - 22
IS  - 3-4
SP  - 283
EP  - 308
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
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  -