Models Of Eye Movement Control Research Articles

COMPLEXITY OF EYE MOVEMENTS IN READING

During reading, our eyes perform complicated sequences of fixations on words. Stochastic models of eye movement control suggest that this seemingly erratic behavior can be attributed to noise in the oculomotor system and random fluctuations in lexical processing. Here, we present a qualitative analysis of a recently published dynamical model [Engbert et al., 2002] and propose that deterministic nonlinear control accounts for much of the observed complexity of eye movement patterns during reading. Based on a symbolic coding technique we analyze robust statistical features of simulated fixation sequences.

Theoretical perspectives on eye movements in reading: Past controversies, current issues, and an agenda for future research

The study of eye movements has become a well established and widely used methodology in experimental reading research. This Introduction provides a survey of some key methodological issues, followed by a discussion of major trends in the development of theories and models of eye movement control in fluent reading. Among the issues to be considered in future research are problems of methodology, a stronger grounding in basic research, integration with the neighbouring area of research on single word recognition, more systematic approaches to model evaluation and comparison, and more work on individual variation and effects of task demands in reading.

Length, frequency, and predictability effects of words on eye movements in reading

We tested the effects of word length, frequency, and predictability on inspection durations (first fixation, single fixation, gaze duration, and reading time) and inspection probabilities during first‐pass reading (skipped, once, twice) for a corpus of 144 German sentences (1138 words) and a subset of 144 target words uncorrelated in length and frequency, read by 33 young and 32 older adults. For corpus words, length and frequency were reliably related to inspection durations and probabilities, predictability only to inspection probabilities. For first‐pass reading of target words all three effects were reliable for inspection durations and probabilities. Low predictability was strongly related to second‐pass reading. Older adults read slower than young adults and had a higher frequency of regressive movements. The data are to serve as a benchmark for computational models of eye movement control in reading.

E-Z Reader 7 provides a platform for explaining how low- and high-level linguistic processes influence eye movements

E-Z Reader 7 is a processing model of eye-movement control. One constraint imposed on the model is that high-level cognitive processes do not influence eye movements unless normal reading processes are disturbed. I suggest that this constraint is unnecessary, and that the model provides a sensible architecture for explaining how both low- and high-level processes influence eye movements.

On keeping word order straight

E-Z Reader is a highly successful model of eye-movement control, employing the notion of a serial-sequential attentional spotlight switched from word to word. Evidence of parallel processing of words in text calls this notion into question. Modifications to the model to accommodate this evidence are possible but will not address the fundamental objection that reading should not be seen as “surrogate listening.”

Reading the scene: Application of E-Z Reader to object and scene perception

We discuss five basic principles of E-Z Reader in terms of their potential for models of eye-movement control in object and scene perception. We identify several obstacles which may hinder the extrapolation of the E-Z Reader principles to nonreading tasks, yet find that sufficient similarities remain to justify using E-Z Reader as a guide for modeling eye-movement control in object and scene perception.

Reading disappearing text: cognitive control of eye movements.

Participants read sentences containing high- or low-frequency target words under normal reading conditions or disappearing-text conditions (in which the word that was fixated disappeared after 60 ms). Even though the fixated word had disappeared after 60 ms, there was still a robust frequency effect wherein readers fixated longer on low-frequency words than on high-frequency words. Thus, the results are consistent with cognitive-control models of eye movement control and inconsistent with visual/oculomotor-control models. Although the uptake of visual information is clearly important for reading, it is the cognitive processes associated with understanding the fixated words that drive the eyes through the text.

Early peripheral and foveal processing in fixations during scene perception

To compare early foveal and peripheral information extraction, visual scenes were masked either foveally or peripherally during the initial part of fixations, using an eye-movement contingent display-change technique. The sequential attention model of eye-movement control predicts a substantial effect of early foveal masking, and early peripheral masking should not affect the ongoing processing. Foveal masking indeed postponed foveal processing as reflected by a considerable increase of average fixation durations with longer masking (Experiments 1 and 3). However, there was also an effect of peripheral masking, mainly on the saccade target selections with an increased number of fixations (Experiment 3) in conjunction with smaller saccade amplitudes (Experiments 2 and 3). Overall, scene perception was more influenced by early foveal masking than by early peripheral masking, and this is partly in agreement with the sequential attention model of eye-movement control.

Parafoveal-on-foveal interactions in word recognition.

An experiment is reported in which participants read sequences of five words, looking for items describing articles of clothing. The third and fourth words in critical sequences were defined as "foveal" and "parafoveal" words, respectively. The length and frequency of foveal words and the length, frequency, and initial-letter constraint of parafoveal words were manipulated. Gaze and refixation rate on the foveal word were measured as a function of properties of the parafoveal word. The results show that measured gaze on a given foveal word is systematically modulated by properties of an unfixated parafoveal word. It is suggested that apparent inconsistencies in previous studies of parafoveal-on-foveal effects relate to a failure to control for foveal word length and hence the visibility of parafoveal words. A serial-sequential attention-switching model of eye movement control cannot account for the pattern of obtained effects. The data are also incompatible with various forms of parallel-processing model. They are best accounted for by postulating a process-monitoring mechanism, sensitive to the simultaneous rate of acquisition of information from foveal and parafoveal sources.

A dynamical model of saccade generation in reading based on spatially distributed lexical processing

The understanding of the control of eye movements has greatly benefited from the analysis of mathematical models. Currently most comprehensive models include sequential shifts of visual attention. Here we propose an alternative model of eye movement control, which includes three new principles: spatially distributed lexical processing, a separation of saccade timing from saccade target selection, and autonomous (random) generation of saccades with foveal inhibition. These three features provide a common control mechanism for fixations, refixations, and regressions. Consequently, the model is called SWIFT (Saccade-generation with inhibition by foveal targets). Results from numerical simulations are in good agreement with effects of word frequency on single-fixation, first-fixation, and gaze durations as well as fixation and word skipping probabilities in first-pass analysis. The model inherently produces complex eye movement patterns including refixations and regressions due to its underlying dynamical principles.

Mathematical models of eye movements in reading: a possible role for autonomous saccades.

An efficient method for the exact numerical simulation of semi-Markov processes is used to study minimal models of the control of eye movements in reading. When we read a text, typical sequences of fixations form a rather complicated trajectory - almost like a random walk. Mathematical models of eye movement control can account for this behavior using stochastic transition rules between few discrete internal states, which represent combinations of certain stages of lexical access and saccade programs. We show that experimentally observed fixation durations can be explained by residence-time-dependent transition probabilities. Stochastic processes with this property are known as semi-Markov processes. For our numerical simulations we use the minimal process method (Gillespie algorithm), which is an exact and efficient simulation algorithm for this class of stochastic processes. Within this mathematical framework, we study different forms of coupling between eye movements and shifts of covert attention in reading. Our model lends support to the existence of autonomous saccades, i.e., the hypothesis that initiations of saccades are not completely determined by lexical access processes.

Eye movement control in reading: accounting for initial fixation locations and refixations within the E-Z Reader model

Reilly and O’Regan (1998, Vision Research, 38, 303–317) used computer simulations to evaluate how well several different word-targeting strategies could account for results which show that the distributions of fixation locations in reading are systematically related to low-level oculomotor variables, such as saccade distance and launch site [McConkie, Kerr, Reddix & Zola, (1988). Vision Research, 28, 1107–1118]. Their simulation results suggested that fixation locations are primarily determined by word length information, and that the processing of language, such as the identification of words, plays only a minimal role in deciding where to move the eyes. This claim appears to be problematic for our model of eye movement control in reading, E-Z Reader [Rayner, Reichle & Pollatsek (1998). Eye movement control in reading: an overview and model. In G. Underwood, Eye guidance in reading and scene perception (pp. 243–268). Oxford, UK: Elsevier; Reichle, Pollatsek, Fisher & Rayner (1998). Psychological Review, 105, 125–157], because it assumes that lexical access is the engine that drives the eyes forward during reading. However, we show that a newer version of E-Z Reader which still assumes that lexical access is the engine driving eye movements also predicts the locations of fixations and within-word refixations, and therefore provides a viable framework for understanding how both linguistic and oculomotor variables affect eye movements in reading.

Toward a model of eye movement control in reading.

The authors present several versions of a general model, titled the E-Z Reader model, of eye movement control in reading. The major goal of the modeling is to relate cognitive processing (specifically aspects of lexical access) to eye movements in reading. The earliest and simplest versions of the model (E-Z Readers 1 and 2) merely attempt to explain the total time spent on a word before moving forward (the gaze duration) and the probability of fixating a word; later versions (E-Z Readers 3-5) also attempt to explain the durations of individual fixations on individual words and the number of fixations on individual words. The final version (E-Z Reader 5) appears to be psychologically plausible and gives a good account of many phenomena in reading. It is also a good tool for analyzing eye movement data in reading. Limitations of the model and directions for future research are also discussed.

Toward a model of eye movement control in reading.

Toward a model of eye movement control in reading.

Eye movement control in reading and visual search: Effects of word frequency

Eye movements were recorded as subjects either read text or searched through texts for a target word. In the reading task, there was a robust word frequency effect wherein readers looked longer at low-frequency words than at high-frequency words. However, there was no frequency effect in the search task. The results suggest that decisions to move the eyes during reading are made on a different basis than they are during visual search. Implications for current models of eye movement control in reading are discussed.

Eye movements and fixation characteristics in perception of stationary scenes: normal subjects as compared to patients with visual neglect or hemianopia

Saccade amplitudes, fixation times, and the spatial distribution of fixation points were comparatively studied in patients with visual hemineglect and/or homonymous hemianopia, as well as in normals (each group, n = 8). Two types of picture slides were presented (with and without search task) while eye movements were recorded with the infrared reflection technique. Self-developed software served to detect fixations, and to document their spatio-temporal parameters. Spectra of saccade amplitudes and fixation times were characteristic of each slide, while exhibiting notable similarities across subject groups. It is concluded that foveal information processing may not be much different in patients and in normals. Average saccade amplitudes and total scanpath lengths across all pictures were significantly smaller in the patients than in normals with both types of slides. In the neglect patients, saccades starting and terminating in the unaffected visual hemifield were larger, on an average, than those entirely located in the affected hemifield. The same was true for many of the hemianopic patients. Nevertheless, during free exploration, mean amplitudes of saccades restricted to the unaffected hemifield of the patients were apparently still smaller than those of normal controls within the corresponding hemifield. Average dwell time of fixations, total fixation time, as well as the total number of fixations did not vary significantly between groups. However, in the patient groups, average fixation times were shorter after large as compared to small saccades. This finding is discussed in the context of saccadic programming on the background of the sequential attention model of eye movement control. In subsamples of five hemianopic and six neglect patients, asymmetry in the distribution of fixation points was compared before and after a 4-week period of comprehensive rehabilitation that Included computerized scanning and attentional training. Only patients with pure hemianopia (who were less severely impaired from the beginning) improved according to this criterion, while neglect patients remained unchanged or deteriorated slightly. Total scanpath lengths, however, were not significantly different before and after therapy in any of the two groups of patients, indicating a persisting disturbance in scanning performance also in the hemianopic group.

Eye movement control during reading: fixation measures reflect foveal but not parafoveal processing difficulty.

The main purpose of this study was to determine whether, during natural reading, the difficulty of the upcoming parafoveal word affects eye movement behaviour on the currently fixated word. A model in which visual attention is allocated in parallel over both the fixated and the upcoming parafoveal word predicts such as effect, while a sequential attention allocation model in which attention is directed first to the fixated word and then to the upcoming parafoveal word, does not. The data reported here show that neither the frequency nor the combined length, frequency and class of the upcoming word affect eye movement behaviour on the current word. These data support the sequential attention--parallel programming model of eye movement control in reading.

Eye movements and scene perception.

Research on eye movements and scene perception is reviewed. Following an initial discussion of some basic facts about eye movements and perception, the following topics are discussed: (I) the span of effective vision during scene perception, (2) the role of eye movements in scene perception, (3) integration of information across saccades, (4) scene context, object identification and eye movements, and (5) the control of eye movements. The relationship of eye movements during reading to eye movements during scene perception is considered. A preliminary model of eye movement control in scene perception is described and directions for future research are suggested.

Eye movement guidance in reading: The role of parafoveal letter and space information.

The relation between parafoveal letter and space information in eye movement guidance during reading was investigated in 2 experiments. Contingent upon the reader's fixation, the type of parafoveal information available to the right of fixation was varied by (a) space information only, (b) space information with letter information added at some delay, or (c) letter and space information simultaneously. In addition, the onset of the relevant parafoveal information was delayed between 0 and 250 ms into the fixation. The time course of processing the 2 types of information (letters or spaces) differed, as did the nature of their impact on the eye movement record. Although both letter and space information influenced saccade length and initial landing positions within words, only letter information had an effect on fixation duration. In addition, fixation duration was affected only by information entering within the first 50 ms of the fixation, whereas saccade length was affected by information arriving at any time during the fixation. The results are consistent with a model of eye movement control in which 2 independent processes are operating in tandem to determine when and where to move the eyes during reading.

Relation between Attention and Characteristics of Saccade during Tracking Eye Movement

AbstractUntil now a satisfactory tracking eye movement control model has not been constructed. It is understood that the tracking eye movement characteristics are affected by the attention of the subject, for which, however, no study has been made. This paper considers the visual feedback called target brightness feedback, where the information concerning the accuracy of tracking and the moving target is fed back to the subject through the change of brightness of the target. By this method, the attention of the subject tracking a moving target is invoked. The saccadic motion is especially examined in detail. The saccade is observed to decrease with the increase of attention. As a result of more detailed analysis, it was observed that the position error at the start of the saccade is increased and the ratio of the saccadic amplitude to the position error is decreased. Those properties can be accounted for on the control model as the enlargement of the saccadic dead zone, and the decrease of the adjusting gain for position error, which is a new‐control element added to the model. It was also examined at which point on the retina the target is recognized. There was observed a tendency that the tracking is made at the periphery with the increase of attention. Those phenomena are considered as due to the avoidance of saccadic suppression.