Saccade Length Research Articles

Intelligent Human Operator Mental Fatigue Assessment Method Based on Gaze Movement Monitoring

Modern mental fatigue detection methods include many parameters for evaluation. For example, many researchers use human subjective evaluation or driving parameters to assess this human condition. Development of a method for detecting the functional state of mental fatigue is an extremely important task. Despite the fact that human operator support systems are becoming more and more widespread, at the moment there is no open-source solution that can monitor this human state based on eye movement monitoring in real time and with high accuracy. Such a method allows the prevention of a large number of potential hazardous situations and accidents in critical industries (nuclear stations, transport systems, and air traffic control). This paper describes the developed method for mental fatigue detection based on human eye movements. We based our research on a developed earlier dataset that included captured eye-tracking data of human operators that implemented different tasks during the day. In the scope of the developed method, we propose a technique for the determination of the most relevant gaze characteristics for mental fatigue state detection. The developed method includes the following machine learning techniques for human state classification: random forest, decision tree, and multilayered perceptron. The experimental results showed that the most relevant characteristics are as follows: average velocity within the fixation area; average curvature of the gaze trajectory; minimum curvature of the gaze trajectory; minimum saccade length; percentage of fixations shorter than 150 ms; and proportion of time spent in fixations shorter than 150 milliseconds. The processing of eye movement data using the proposed method is performed in real time, with the maximum accuracy (0.85) and F1-score (0.80) reached using the random forest method.

The role of perceptual and word identification spans in reading efficiency: Evidence from hearing and deaf readers.

Theories of reading posit that decisions about "where" and "when" to move the eyes are driven by visual and linguistic factors, extracted from the perceptual span and word identification span, respectively. We tested this hypothesized dissociation by masking, outside of a visible window, either the spaces between the words (to assess the perceptual span, Experiment 1) or the letters within the words (to assess the word identification span, Experiment 2). We also investigated whether deaf readers' previously reported larger reading span was specifically linked to one of these spans. We analyzed reading rate to test overall reading efficiency, as well as average saccade length to test "where" decisions and average fixation duration to test "when" decisions. Both hearing and deaf readers' perceptual spans extended between 10 and 14 characters, and their word identification spans extended to eight characters to the right of fixation. Despite similar sized rightward spans, deaf readers read more efficiently overall and showed a larger increase in reading rate when leftward text was available, suggesting they attend more to leftward information. Neither rightward span was specifically related to where or when decisions for either group. Our results challenge the assumed dissociation between type of reading span and type of saccade decision and indicate that reading efficiency requires access to both perceptual and linguistic information in the parafovea. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

A design for neural network model of continuous reading

Cognition and learning are exceedingly modeled as an associative activity of connectionist neural networks. However, only a few such models exist for continuous reading, which involves the delicate coordination of word recognition and eye movements. Moreover, these models are limited to only orthographic level of word processing with predetermined lexicons. Here, we present a conceptual design of a developmentally plausible neural network model of reading designed to simulate word learning, parafoveal preview activation of words, their later foveal word recognition including phonological decoding, and forward saccade length as a control mechanism for intake of new textual information. We will discuss the theoretical advancements of the design and avenues for future developments.

Visually encoding orthogonal planar graph drawings as graph mazes: An eye tracking study

There are various styles to visually represent relational data in the form of node-link diagrams. In particular, for planar graphs we can find orthogonal node-link diagrams consisting of links bending only at ninety degrees a successful and prominent variant. One of the benefits of such drawings is the tracking of longer paths through a network with the eyes due to their limited number of link orientations, changes, and variations, but on the negative side the links can have arbitrary bending shapes. In this article we developed a novel way to visualize such orthogonal planar drawings by making use of mazes that look more natural to the human eye due to the street-like visual metaphor that many people are familiar with. Tracking paths is one of the major tasks in such graph visualizations, similar to orthogonal node-link diagrams, however, we argue that mazes are a more natural way to find paths. To get insights in the visual scanning behavior when reading graph mazes we conducted a comparative eye tracking study with 26 male versus female participants of different experience levels while also alternating between orthogonal node-link drawings and graph mazes as well as different graph size levels. The major result of this comparative study is that the participants can track paths in both representation styles, including a geodesic path tendency in their visual search behavior, but typically have a longer fixation duration at branching nodes and locations in the mazes that lead to opposite directions to the geodesic path tendency, maybe the viewers had to start a reorientation phase in their visual scanning behavior. We also found out that the size, that is the number of graph vertices has an impact on the visual scanning behavior for both orthogonal node-link diagrams as well as street-like maze representations, but for the mazes we found this impact to be less strong (in terms of the eye movement data metrics fixation durations and saccade lengths) compared to the node-link diagrams. To conclude the article, we discuss limitations and scalability issues of our approach. Moreover, we give an outlook and future work for possible extensions.

Saccadic targeting in the Landolt-C task: Implications for Chinese reading.

Participants in an eye-movement experiment performed a modified version of the Landolt-C paradigm (Williams & Pollatsek, 2007) to determine if there are preferred viewing locations when they searched for target squares embedded in linear arrays of spatially contiguous clusters of squares (i.e., sequences of one to four squares having missing segments of variable size and orientation). The results of this experiment indicate that, although the peaks of the single- and first-of-multiple-fixation landing-site distributions were respectively located near the centers and beginnings of the clusters, thereby replicating previous patterns that have been interpreted as evidence for the default saccadic-targeting hypothesis, the same dissociation was evident on nonclusters (i.e., arbitrarily defined regions of analysis). Furthermore, properties of the clusters (e.g., character number and gap size) influenced fixation durations and forward saccade length, suggesting that ongoing stimulus processing affects decisions about when and where (i.e., how far) to move the eyes. Finally, results of simulations using simple oculomotor-based, default-targeting, and dynamic-adjustment models indicated that the latter performed better than the other two, suggesting that the dynamic-adjustment strategy likely reflects the basic perceptual and motor constraints shared by a variety of visual tasks, rather than being specific to Chinese reading. The theoretical implications of these results for existing and future accounts of eye-movement control are discussed. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Visual perception of facial expressions of emotions and alexithymia among people suffering from schizophrenia

Aim of the studyThe aim of the study is to find out whether there is a relationship between the severity of alexithymia and the visual perception of facial expressions of emotions among people suffering from schizophrenia.Subject or material and methods41 people suffering from schizophrenia and 41 healthy people participated in the study. In the first stage, the subjects completed the Toronto Alexithymia Scale (TAS-20) questionnaire. The second stage was based on eye-tracking measurements made during a computer experiment of recognising facial expressions.ResultsPeople with schizophrenia showed significantly higher intensity of alexithymia than healthy people. In the group of patients with schizophrenia, a negative correlation between alexithymia and the length of saccades on the nose was found.DiscussionIn the group of people with schizophrenia, alexithymia is associated with less intensive exploration of the nasal area. A wrinkled nose is an important area, first of all, in the manifestation of negative emotions, in recognition of which the sick people make the most mistakes.ConclusionsProblems with recognising emotions in people suffering from schizophrenia are associated with neuronal dysfunction and abnormalities in the eye movement. These factors disrupt the early stages of sensory processing. The relationship of alexithymia with the visual perception of patients with schizophrenia suggests that top-down processes may also contribute to the development of these deficits.

Reliability of a Tablet Computer-Based Dyslexia Screening Application Using an Eye-Tracking System

Purpose: The early detection and management of dyslexia are crucial for preventing irreversible educational gaps and various negative consequences for affected students. However, diagnosing dyslexia is challenging because it requires a comprehensive assessment. Dyslexia screening tests that utilize fast, automated, computer-based technology can be useful for early identification and management. In this paper, we introduce a tablet computer-based dyslexia screening application that uses an eye-tracking system and verify its reliability.Methods: The study included 200 participants between 8 and 13 years of age from an elementary school, all of whom underwent dyslexia screening tests twice. The screening was conducted using the VisualCamp SeeSo eye-tracking Android Software Development Kit v3.0.0, implemented on Samsung Galaxy Tab S5e tablets. The eye-tracking system measured reading speed by gaze, mean gaze fixation time, gaze fixation frequency, saccadic length, and regression ratio. To assess the reliability of the two sets of measurements, the intraclass correlation coefficient (ICC) was employed.Results: Excellent reliability was found for measurements of gaze fixation frequency (ICC=0.83), gaze fixation mean time (ICC=0.82), and reading speed by gaze (ICC=0.76), and good reliability for measurements of regression ratio (ICC=0.75) and saccadic length (ICC=0.72).Conclusion: This study demonstrated that the tablet computer-based dyslexia screening application reliably measured eye movements in subjects with dyslexia. Furthermore, the application proved to be highly reliable and potentially suitable for use in clinical or school settings, eliminating the need for a laboratory environment and extensive equipment.

What is the Difference between Good and Poor Young Adult Readers?

This study investigated demographic profiles, reading characteristics and processes of good and poor young adult readers. Data were collected from 149 undergraduate students studying at a state university in Türkiye through a questionnaire set and eye-tracking experiments. Groups of this study – good and poor readers – were defined according to their performance in a combination of three reading comprehension tests and an oral reading skills test. As a result, significant differences were found between good and poor young adult readers in terms of their ages, genders, the number of books they have in their libraries, and eye movements such as saccade and fixation counts, saccade length, dwell time, and regressions but no differences in their reading habits, strategies, and attitudes, parents’ educational and economic levels, educational backgrounds, and saccade and fixation duration. Concentrating on several components of reading, this study thus provides a comprehensive perspective on the differences between good and poor readers.

Cross-linguistic comparison in reading sentences of uniform length: Visual-perceptual demands override readers' experience.

Accurate saccadic targeting is critical for efficient reading and is driven by the sensory input under the eye-gaze. Yet whether a reader's experience with the distributional properties of their written language also influences saccadic targeting is an open debate. This study of Russian sentence reading follows Cutter et al.'s (2017) study in English and presents readers with sentences consisting of words of the same length. We hypothesised that if the readers' experience matters as per discrete control account, Russian readers would produce longer saccades and farther landing positions than the ones produced by English readers. On the contrary, if the saccadic targeting is primarily driven by the immediate perceptual demands that override readers' experience as per the dynamic adjustment account, the saccades of Russian and English readers would be of the same length, resulting in similar landing positions. The results in both Cutter et al. and the present study provided evidence for the latter account: Russian readers showed rapid and accurate adjustment of saccade lengths and landing positions to the highly constrained input. Crucially, the saccade lengths and landing positions did not differ between English and Russian readers even in the cross-linguistically length-matched stimuli.

Planning to revisit: Neural activity in refixation precursors.

Eye tracking studies suggest that refixations-fixations to locations previously visited-serve to recover information lost or missed during earlier exploration of a visual scene. These studies have largely ignored the role of precursor fixations-previous fixations on locations the eyes return to later. We consider the possibility that preparations to return later are already made during precursor fixations. This process would mark precursor fixations as a special category of fixations, that is, distinct in neural activity from other fixation categories such as refixations and fixations to locations visited only once. To capture the neural signals associated with fixation categories, we analyzed electroencephalograms (EEGs) and eye movements recorded simultaneously in a free-viewing contour search task. We developed a methodological pipeline involving regression-based deconvolution modeling, allowing our analyses to account for overlapping EEG responses owing to the saccade sequence and other oculomotor covariates. We found that precursor fixations were preceded by the largest saccades among the fixation categories. Independent of the effect of saccade length, EEG amplitude was enhanced in precursor fixations compared with the other fixation categories 200 to 400 ms after fixation onsets, most noticeably over the occipital areas. We concluded that precursor fixations play a pivotal role in visual perception, marking the continuous occurrence of transitions between exploratory and exploitative modes of eye movement in natural viewing behavior.

Optical and motor changes associated with lighting and near vision tasks in electronic devices.

Purpose: To assess optical and motor changes associated with near vision reading under different controlled lighting conditions performed with two different types of electronic screens. Methods: Twenty-four healthy subjects with a mean age of 22.9±2.3 years (18- 33) participated in this study. An iPad and an e-ink reader were chosen to present calibrated text, and each task lasted 5 minutes evaluating both ambient illuminance level and luminance of the screens. Results: Eye-tracker data revealed a higher number of saccadic eye movements under minimum luminance than under maximum luminance. The results showed statistically significant differences between the iPad (p=0.016) and the e-ink reader (p=0.002). The length of saccades was also higher for the minimum luminance level for both devices: 6.2±2.8 mm and 8.2±4.2 mm (e-ink max vs min), 6.8±2.9 mm and 7.6±3.6 mm (iPad max vs min), and blinking rate increased significantly for lower lighting conditions. Conclusions: Performing reading tasks on electronic devices is highly influenced by both the configuration of the screens and the ambient lighting, meanwhile, low differences in visual quality that are transient in healthy young people, were found.

Are there preferred viewing locations in Chinese reading? Evidence from eye-tracking and computer simulations.

The Chinese writing system is different from English in that individual words both comprise one to four characters and are not separated by clear word boundaries (e.g., interword spaces). These differences raise the question of how readers of Chinese know where to move their eyes to support efficient lexical processing? The widely accepted default-targeting hypothesis suggests that Chinese readers direct their eyes to a small number of preferred-viewing locations (PVLs), such as the beginning or middle of upcoming words. In this article, we report two eye-movement experiments testing this hypothesis. In both experiments, participants read sentences comprising entirely two-character words, but either without (Experiment 1) or with (Experiment 2) explicit knowledge of this structure prior to their participation. The results of both experiments indicate the absence of PVLs. Simulations using implemented versions of a simple oculomotor-based hypothesis, two variants of the default-targeting hypothesis, and the hypothesis that saccade lengths are modulated as a function of estimated parafoveal-processing difficulty (i.e., dynamic-adjustment hypothesis) suggest that the latter provides the best account of saccadic-targeting during Chinese reading. These results are discussed in relation to broader issues of eye-movement control during reading and how models of such must be modified to provide more accurate accounts of the reading of Chinese and other languages. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Eye-Tracker Study of the Developmental Eye Movement Test in Young People without Binocular Dysfunctions.

The purpose of this study was to evaluate ocular motility in normal young adults when performing the Developmental Eye Movement (DEM) test using an infrared eye-tracker in a sample of young subjects without visual dysfunctions. An optometric evaluation was carried out on 52 participants with a mean age of 21.00 ± 3.22 years to verify they did not have any binocular dysfunction, by completing a computerized version of the DEM test while their eye movements were recorded with an eye-tracker. A custom-written software was developed to analyse some specific parameters of ocular motility while performing each subtest (Test A, Test B and Test C) of the complete DEM test. The mean duration of the fixations was shorter in Test C (243.56 ± 46.18 s) than in Test A (493.52 ± 171.41 s) and Test B (484.20 ± 156.59 s). The mean adjusted horizontal (AdjHT: 35.24 ± 6.68 s) and vertical (VT: 33.58 ± 5.56 s) times were at the 45th and at the 40th percentile, respectively. In Test C, there was a high positive significant correlation between the saccadic speed (cc: 0.77; p < 0.001) and the saccadic length (cc: 0.74; p < 0.001) of both eyes. The eye-tracker is an objective method to evaluate the DEM test in subjects without binocular dysfunctions, measuring and quantifying ocular motility parameters that are impossible with the traditional subjective method. The eye movements of both eyes are conjugated in each subject, having saccades of the same length and speed.

A cross-linguistic study of spatial parameters of eye-movement control during reading.

Current theories of oculomotor control in reading differ in their accounts of saccadic targeting. Some argue that targets for saccades are solely selected on the basis of the rapidly changing sensory input, whereas others additionally allow for the reader's experiential biases to modulate saccade lengths. We investigated this debate using cross-linguistic data on text reading in 12 alphabetic languages from the Multilingual Eye-Movement Corpus (MECO) database. These languages vary widely in their word length distributions, suggesting that expected word lengths and corresponding biases toward optimal saccade lengths may also vary across readers of these languages. Regression analyses confirmed that readers of languages with longer words (e.g., Finnish) rather than shorter words (e.g., Hebrew) landed further into the word, even when sensory aspects relevant for saccade planning (e.g., word lengths) were controlled for. In the prevalent saccade type, a one-letter difference in mean word length between languages came with one-quarter-letter of a difference in initial landing position and saccade length, and a decrease in 1.5% in refixation probability. Interpreted in the Bayesian framework, the findings highlight the relevance of global language-wide settings for accounts of spatial oculomotor control and lead to testable predictions for further cross-linguistic research. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Music reading experience modulates eye movement pattern in English reading but not in Chinese reading

Here we tested the hypothesis that in Chinese-English bilinguals, music reading experience may modulate eye movement planning in reading English but not Chinese sentences due to the similarity in perceptual demands on processing sequential symbol strings separated by spaces between music notation and English sentence reading. Chinese–English bilingual musicians and non-musicians read legal, semantically incorrect, and syntactically (and semantically) incorrect sentences in both English and Chinese. In English reading, musicians showed more dispersed eye movement patterns in reading syntactically incorrect sentences than legal sentences, whereas non-musicians did not. This effect was not observed in Chinese reading. Musicians also had shorter saccade lengths when viewing syntactically incorrect than correct musical notations and sentences in an unfamiliar alphabetic language (Tibetan), whereas non-musicians did not. Thus, musicians’ eye movement planning was disturbed by syntactic violations in both music and English reading but not in Chinese reading, and this effect was generalized to an unfamiliar alphabetic language. These results suggested that music reading experience may modulate perceptual processes in reading differentially in bilinguals’ two languages, depending on their processing similarities.

Skipping the structural particle de () in reading Chinese: The role of word frequency and sentential fit.

Previous studies suggested that readers were more likely to skip a word when it was previewed by a very-high-frequency word, like "the" in English and "de ()" in Chinese, and they suggested that readers based skipping decisions on parafoveal word information rather than on sentence context. However, in these studies, the very-high-frequency preview word (the or de) was always implausible given the sentence context. It is an open question whether parafoveal word information interacts with sentence context to influence skipping decisions. Therefore, the current experiment orthogonally manipulated the preview information of the target character (identical or de preview) and the plausibility of de (plausible or implausible) to examine this question. The major results indicated that readers were more likely to skip the target character and made longer outgoing saccade length across the boundary in the de preview condition than in the identical preview condition. What is more important, the interaction between the plausibility of de and preview condition was significant: Readers' higher probability of skipping the target character and longer outgoing saccade length in the de preview condition than in the identical preview condition was only significant when de was plausible, suggesting that parafoveal word information and context information can act as a joint constraint on skipping decision in reading Chinese.

A dynamic adjustment model of saccade lengths in reading for word-spaced orthographies: evidence from simulations and invisible boundary experiments

ABSTRACT Contemporary models of eye movement control in reading assume a discrete target word selection process preceding saccade length computation, while the selection itself is assumed to be driven by word identification processes. However, a potentially more parsimonious, dynamic adjustment view allows both next word length and its content (e.g. orthographic) to modulate saccade length in a continuous manner. Based on a recently proposed center-based saccade length account a new regression model of forward saccade length is introduced and validated in a simulation study. Further, additional simulations and gaze-contingent invisible boundary experiments were used to study the cognitive mechanisms underlying skipping. Overall, the results support the plausibility of dynamic adjustment of saccade length in word-spaced orthographies. In the future, the present regression formula-based computational model will allow a straightforward implementation of influences of current and next word content (visual, orthographic, or contextual) on saccade length computation.

The role of L1 reading direction on L2 perceptual span: An eye-tracking study investigating Hindi and Urdu speakers

In the current study we used the gaze-contingent moving window paradigm to directly compare the second language (L2) English perceptual span of two groups that speak languages with essentially the same lexicon and grammar but crucially with different writing directions (and scripts): Hindi (read left to right) and Urdu (read right to left). This is the first study to directly compare first language (L1) speakers of languages that differ primarily in reading direction in a common L2, English. While Urdu speakers had a slightly faster reading rate, we found no additional differences between Hindi and Urdu speakers when reading L2 English; both groups showed a perceptual span between 9 and 11 characters to the right of the fixation based on saccade length. This suggests little to no influence of L1 reading direction on L2 perceptual span, but rather that L2 perceptual span is influenced by allocation of attention during reading. Our data are in line with research by Leung et al. (2014) finding that L2 speakers have a smaller perceptual span than native speakers (L1 perceptual span is approximately 15 characters to the right of the fixation). This most likely stems from the increased demands associated with reading in a second language, which led to a reduction in the amount of attention that can be allocated outside of the current fixation.

Deafness enhances perceptual span size in Chinese reading: Evidence from a gaze-contingent moving-window paradigm.

Using a gaze-contingent moving-window paradigm, we investigated whether/how deafness affects perceptual processing in Chinese reading. Besides the manipulation of window size, word length of sentences used in the experiment was also manipulated to check whether deafness enhanced the word length effect on perceptual span. Significant interactions of window constraints and deafness and a three-way interaction were observed on reading rate. Smaller effects of window constraints for deaf Chinese readers and nonreliable three-way interactions were observed on forward saccade length. This suggests that deaf Chinese readers exhibit a larger perceptual span, and word length affected the span from which information was acquired for comprehension whereas both deafness and word length might have little impact on the span from which information is acquired for oculomotor targeting during natural reading of Chinese.

Let Me Make You Happy, and I'll Tell You How You Look Around: Using an Approach-Avoidance Task as an Embodied Emotion Prime in a Free-Viewing Task.

The embodied approach of human cognition suggests that concepts are deeply dependent upon and constrained by an agent's physical body's characteristics, such as performed body movements. In this study, we attempted to broaden previous research on emotional priming, investigating the interaction of emotions and visual exploration. We used the joystick-based approach-avoidance task to influence the emotional states of participants, and subsequently, we presented pictures of news web pages on a computer screen and measured participant's eye movements. As a result, the number of fixations on images increased, the total dwell time increased, and the average saccade length from outside of the images toward the images decreased after the bodily congruent priming phase. The combination of these effects suggests increased attention to web pages' image content after the participants performed bodily congruent actions in the priming phase. Thus, congruent bodily interaction with images in the priming phase fosters visual interaction in the subsequent exploration phase.