Eye Movements In Visual Search Research Articles

The influence of the stimulus category on the characteristics of eye movements in visual search

Introduction. The speed and efficiency of visual search are important characteristics of the activities of a significant range of specialists working with visual information. Specialists have carefully studied the features of visual search from the point of view of cognitive psychology and in connection with the modeling of oculomotor activity. It has been shown that its effectiveness and the parameters of search eye movements are influenced by both stimulation factors and some cognitive factors (features of the subject's preset, the influence of previous search stages, etc.). We assume that the search features are also related to how well a person represents the desired stimulus: whether it belongs to a familiar semantic category, how accurate and unambiguous its visual representation is.
 The study aims to explore the relationship between the parameters of eye movements in visual search and the features of the mental representation of the target object.
 Materials and methods. We have created sets of stimuli belonging to different semantic categories, characterized by different accuracy of mental representations, but having similar sensory qualities. Each object (both the target stimulus and the distractor) in the search field was a black circle on a white background with four black segments inside. The segments formed one of three configurations: a) a face; b) a Roman numeral; c) a random configuration. The study participants were asked to find in a matrix of 84 objects a specific target stimulus belonging to one of the three specified categories. The scientists recorded the participant's eye movements during the search.
 Results. The results of the study generally confirmed the hypothesis about the relationship of search characteristics with the category of the target object. The smallest number of errors, the minimum duration of fixation and the maximum amplitude of saccades characterized the search for Roman numerals — objects with a well-formed and well-defined visual representation. The most difficult, as expected, was the search for objects representing random configurations of segments.
 Limitations. Since the study was largely exploratory in nature, the results obtained require clarification on a wider sample. It is possible that the characteristics of the search were influenced by such a factor not controlled in the study as the configuration of the lines, namely, the presence or absence of their intersections, which should be taken into account in further work.
 Conclusions. The better the visual representation of the target object is formed, the more successful its search is. In this case, eye movements are characterized by a shorter duration of fixation and a higher frequency of saccades of greater amplitude.
 Ethics. The study was conducted in compliance with the ethical principles set out in the Helsinki Declaration of the World Medical Association, all participants gave voluntary informed consent.

The influence of picture book design on visual attention of children with autism: a pilot study

Taking 22 children with mild and moderate autism as subjects and using the TobiiX 120 eye-tracker to record their eye movements in visual search of images in picture books, the characteristics of the process of autistic children viewing picture books were explored. Two measures, fixation counts and gaze duration, were used alongside attention heatmap, to explore the visual patterns among children with autism viewing two types of researcher-made picture books and an ordinary picture book. Using a within-subject design, it was found that children with autism could sustain longer gaze duration and have more fixation points on the effective area of the picture book content when viewing researcher-made picture books than when viewing the ordinary picture book, suggesting better visual attention to single-object and single-pattern picture books. The study offers insights and support for related picture book reading and teaching in the future.

The Functional Visual Field(s) in simple visual search

During a visual search for a target among distractors, observers do not fixate every location in the search array. Rather processing is thought to occur within a Functional Visual Field (FVF) surrounding each fixation. We argue that there are three questions that can be asked at each fixation and that these imply three different senses of the FVF. 1) Can I identify what is at location XY? This defines a resolution FVF. 2) To what shall I attend during this fixation? This defines an Attentional FVF. 3) Where should I fixate next? This defines an Exploratory FVF. We examine FVFs 2&3 using eye movements in visual search. In three Experiments, we collected eye movements during visual search for the target letter T among distractor letter Ls (Exps 1 and 3) or for a color X orientation conjunction (Exp 2). Saccades that do not go to the target can be used to define the Exploratory FVF. The saccade that goes to the target can be used to define the Attentional FVF since the target was probably covertly detected during the prior fixation. The Exploratory FVF is larger than the Attentional FVF for all three experiments. Interestingly, the probability that the next saccade would go to the target was always well below 1.0, even when the current fixation was close to the target and well within any reasonable estimate of the FVF. Measuring search-based Exploratory and Attentional FVFs sheds light on how we can miss clearly visible targets.

The attentional blink: A relational accountof attentional engagement.

Visual attention allows selecting relevant information from cluttered visual scenes and is largely determined by our ability to tune or bias visual attention to goal-relevant objects. Originally, it was believed that this top-down bias operates on the specific feature values of objects (e.g., tuning attention to orange). However, subsequent studies showed that attention is tuned to in a context-dependent manner to the relative feature of a sought-after object (e.g., the reddest or yellowest item), which drives covert attention and eye movements in visual search. However, the evidence for the corresponding relational account is still limited to the orienting of spatial attention. The present study tested whether the relational account can be extended to explain attentional engagement and specifically, the attentional blink (AB) in a rapid serial visual presentation (RSVP) task. In two blocked conditions, observers had to identify an orange target letter that could be either redder or yellower than the other letters in the stream. In line with previous work, a target-matching (orange) distractor presented prior to the target produced a robust AB. Extending on prior work, we found an equally large AB in response to relatively matching distractors that matched only the relative color of the target (i.e., red or yellow; depending on whether the target was redder or yellower). Unrelated distractors mostly failed to produce a significant AB. These results closely match previous findings assessing spatial attention and show that the relational account can be extended to attentional engagement and selection of continuously attended objects in time.

Multi-step planning of eye movements in visual search

The capability of directing gaze to relevant parts in the environment is crucial for our survival. Computational models have proposed quantitative accounts of human gaze selection in a range of visual search tasks. Initially, models suggested that gaze is directed to the locations in a visual scene at which some criterion such as the probability of target location, the reduction of uncertainty or the maximization of reward appear to be maximal. But subsequent studies established, that in some tasks humans instead direct their gaze to locations, such that after the single next look the criterion is expected to become maximal. However, in tasks going beyond a single action, the entire action sequence may determine future rewards thereby necessitating planning beyond a single next gaze shift. While previous empirical studies have suggested that human gaze sequences are planned, quantitative evidence for whether the human visual system is capable of finding optimal eye movement sequences according to probabilistic planning is missing. Here we employ a series of computational models to investigate whether humans are capable of looking ahead more than the next single eye movement. We found clear evidence that subjects’ behavior was better explained by the model of a planning observer compared to a myopic, greedy observer, which selects only a single saccade at a time. In particular, the location of our subjects’ first fixation differed depending on the stimulus and the time available for the search, which was well predicted quantitatively by a probabilistic planning model. Overall, our results are the first evidence that the human visual system’s gaze selection agrees with optimal planning under uncertainty.

Visual reinforcement shapes eye movements in visual search.

We use eye movements to gain information about our visual environment; this information can indirectly be used to affect the environment. Whereas eye movements are affected by explicit rewards such as points or money, it is not clear whether the information gained by finding a hidden target has a similar reward value. Here we tested whether finding a visual target can reinforce eye movements in visual search performed in a noise background, which conforms to natural scene statistics and contains a large number of possible target locations. First we tested whether presenting the target more often in one specific quadrant would modify eye movement search behavior. Surprisingly, participants did not learn to search for the target more often in high probability areas. Presumably, participants could not learn the reward structure of the environment. In two subsequent experiments we used a gaze-contingent display to gain full control over the reinforcement schedule. The target was presented more often after saccades into a specific quadrant or a specific direction. The proportions of saccades meeting the reinforcement criteria increased considerably, and participants matched their search behavior to the relative reinforcement rates of targets. Reinforcement learning seems to serve as the mechanism to optimize search behavior with respect to the statistics of the task.

Top-down expectancy versus bottom-up guidance in search for known color-form conjunctions.

We assessed the effects of pairing a target object with its familiar color on eye movements in visual search, under conditions where the familiar color could or could not be predicted. In Experiment 1 participants searched for a yellow- or purple-colored corn target amongst aubergine distractors, half of which were yellow and half purple. Search was more efficient when the color of the target was familiar and early eye movements more likely to be directed to targets carrying a familiar color than an unfamiliar color. Experiment 2 introduced cues which predicted the target color at 80 % validity. Cue validity did not affect whether early fixations were to the target. Invalid cues, however, disrupted search efficiency for targets in an unfamiliar color whilst there was little cost to search efficiency for targets in their familiar color. These results generalized across items with different colors (Experiment 3). The data are consistent with early processes in selection being automatically modulated in a bottom-up manner to targets in their familiar color, even when expectancies are set for other colors.

Examining eye movements in visual search through clusters of objects in a circular array

Participants were asked to search for a complete O in an array consisting of eight clusters of four Landolt Cs (i.e., Os with a gap) arranged in a ring. The size of the gap in the Cs varied from cluster to cluster but was held constant within a cluster. The manual response time data were consistent with a serial self-terminating search. More importantly, eye movement data supported a serial processing model as (1) clusters were fixated serially (either clockwise or counterclockwise) on most trials and (2) fixation times on a cluster reflected processing time on that cluster and were unaffected by the gap size of either the prior or succeeding cluster. Furthermore, the pattern of fixation times on a cluster was similar to the pattern of response times in a secondary task where a single cluster was presented at fixation. These data extend our previous findings in which search was through a linear sequence of clusters, and indicate that a serial search pattern through clusters of these kinds of objects is not confined to reading-like linear arrays.

Examining Eye Movements in Visual Search through Clusters of Objects in a Circular Array

Participants were asked to search for a complete O in an array consisting of eight clusters of four Landolt Cs (i.e., Os with a gap) arranged in a ring. The size of the gap in the Cs varied from cl...

The persistent visual store as the locus of fixation memory in visual search tasks

Experiments on visual search have demonstrated the existence of a relatively large and reliable memory for which objects have been fixated; an indication of this memory is that revisits (fixations on previously fixated objects) typically comprise only about 5% of fixations. Any cognitive architecture that supports visual search must account for where such memory resides in the system and how it can be used to guide eye movements in visual search. This paper presents a simple solution for the EPIC architecture that is consistent with the overall requirements for modeling visually-intensive tasks and other visual memory phenomena.

Visual search: The role of peripheral information measured using gaze-contingent displays

Two of the factors limiting progress in understanding the mechanisms of visual search are the difficulty of controlling and manipulating the retinal stimulus when the eyes are free to move and the lack of an ideal observer theory for fixation selection during search. Recently, we developed a method to precisely control retinal stimulation with gaze-contingent displays (J. S. Perry & W. S. Geisler, 2002), and we derived a theory of optimal eye movements in visual search (J. Najemnik & W. S. Geisler, 2005). Here, we report a parametric study of visual search for sine-wave targets added to spatial noise backgrounds that have spectral characteristics similar to natural images (the amplitude spectrum of the noise falls inversely with spatial frequency). Search time, search accuracy, and eye fixations were measured as a function of target spatial frequency, 1/f noise contrast, and the resolution falloff of the display from the point of fixation. The results are systematic and similar for the two observers. We find that many aspects of search performance and eye movement pattern are similar to those of an ideal searcher that has the same falloff in resolution with retinal eccentricity as the human visual system.

Effect of stimulus contrast on performance and eye movements in visual search

According to the visual span control hypothesis, eye movements are controlled in relation to the size of visual span. In reading, the decrease of contrast reduces visual span, saccade sizes, and reading speed. The purpose of the present study is to determine how stimulus contrast affects the speed of two-dimensional visual search and how changes in eye movements and visual span could explain changes in performance. The task of the observer was to search for, and identify, an uppercase letter from a rectangular array of characters in which the other items were numerals. Threshold search time, i.e. the duration of stimulus presentation required for search that is successful with a given probability, was determined by using a multiple-alternative staircase method. Eye movements were recorded simultaneously by using a video eye tracker. Four different set sizes (the sizes of stimulus array) (3×3–10×10), and five different contrasts (0.0186–0.412) were used. At all set sizes, threshold search time decreased with increasing contrast. Also the average number of fixations per search decreased with increasing contrast. At the smallest set size (3×3), only one fixation was needed except at the lowest contrast. Average fixation duration decreased and saccade amplitudes increased slightly with increasing contrast. The reduction of the number of fixations with increasing contrast suggests that visual span, i.e. the area from which information can be collected at one fixation, increases with increasing contrast. The reduction of the number of fixations together with reduced fixation duration result in reduced search times when contrast increases.

Visual search in modern human-computer interfaces

Abstract This article reviews aspects of visual search in relation to computer visual display units. Theoretical issues such as eye movements in visual search are discussed as well as practical examples such as the role of array shape, the benefits of cursor-presented status (insert vs overtype) information, conspicuity of peripherally presented information, and possible benefits of anti-aliased fonts. In association with the four experiments relating to these aspects, the respective follow-up eye movement monitoring studies are also described as these allowed quantification of what otherwise might only have been inferred. The review concludes with four major recommendations. First, much scope remains for exploring the optimization of status (e.g., cursor-presented) information. Second, it would be worth exploring whether icons, like verbal labels, are susceptible to an array shape effect. Third, further work is required (e.g. in the possible role of articulatory differences) in accounting for the ease of...

Oculomotor Control and Cognitive Processes: Normal and Pathological Aspects

Neural networks applied to the oculomotor system (D.A. Robinson). Eye movements in neurological diagnosis: Huntington's disease and congenital nystagmus (D.S. Zee). Neurophysiology of Eye Movements. Localization of targets in humans: the role of ocular muscle proprioception (D. Nommay et al). Effects of severance of the vestibular commissural pathway on the neural integrator of the oculomotor system in cat (E. Godaux, G. Cheron). Representation of three-dimensional eye movements in the cerebellar flocculus of the rabbit (J. van der Steen et al). Effects of floccular injections of noradrenergic agonists and antagonists on adaptive changes in the VOR gain (J. van Neerven et al). The Control of Eye Movements. Human vestibuloocular reflex (VOR) and vestibular velocity storage as influenced by optokinetic stimuli (E. Koenig et al). Vertical gaze stability in cat: otolithic contribution (V.E. Pettorossi et al). Post-rotational nystagmus suppression by the presentation of a single visual target in cat and man (G. Magenes et al). Adaptive mechanisms in the monkey saccadic system (P. Inchingolo et al). Human express saccades: catch trails influence the probability of their occurrence (M. Juttner, W. Wolf). Eye-Head Coordination. Adaptation of eye and head movements to reduced peripheral vision (G.M. Gauthier et al). Coupled and dissociated modes of eye-head coordination in humans to flashed visual target (S. Ron, A. Berthoz). Superior colliculus and feedback control of gaze shift in the head-free cat (D. Pelisson et al). Strategies of eye-head coordination (R. Schmid, D. Zambarbieri). Eye Movements in Pathology. Sensory and motor aspects of congenital nystagmus (R.V. Abadi et al). Head-shaking nystagmus - A clinical tool to detect peripheral and central vestibular asymmetries (M. Fetter et al). Saccadic and smooth pursuit eye movements in olivo-ponto-cerebellar atrophies (M. Spanio et al). Slow eye movement abnormalities in Wallenberg's lateral medullary syndrome (W. Waespe). Eye tracking dysfunctions in schizophrenic patients - Why is there no neuroleptic side-effect? (N. Hock et al). Eye Movements and Cognitive Processes. A mathematical analysis of the convenient viewing position hypothesis and its components (M. Brysbaert, G. d'Ydewalle). Is there an optimal landing position in words during reading of texts? (F. Vitu, J.K. O'Regan). Processing of prepositions as reflected by gaze durations (A. Wilbertz et al). The latency of saccadic eye movements to texture-defined stimuli (H. Deubel, H. Frank). Does thinking aloud influence the structure of cognitive processes? (U. Lass et al). Eye movements in visual search: a test of the limited cognitive effort hypothesis and an analysis of the search operating characteristic (A.M. Jacobs). Applied Research. Colour, effective contrast and search performance (J.L. Barbur et al). Video-oculography - An alternative method for measurement of three-dimensional eye movements (A.H. Clarke et al).

Search performance without eye movements

Visual search performance (with sets chosen to elicit both serial and parallel search patterns) under two conditions that precluded saccades was compared to the typical situation in which visual inspection of the array is possible. In one condition, the display duration was so brief that any saccades that were executed would be too late to bring the targeted portion of the array into the fovea. In the other, the display remained present until the subject's response, but eye position was monitored and trials with shifts in fixation were excluded from analysis. The latter condition produced search latencies that were nearly identical to those with free inspection. Brief exposure, in contrast, did not produce the pattern typical of serial search, presumably because of strategies induced to deal with the rapid decay of the visual array. It is concluded that saccadic eye movements play little role in the patterns of performance used to infer serial and parallel search, and that brief exposure is not a satisfactory technique for exploring the role of saccadic eye movements in visual search.

視覚的探索中の背景文字処理と眼球運動

視覚的探索中の背景文字処理と眼球運動

Spatial and/or temporal adjustments of scanning behavior to visibility changes

This paper continues a series of studies focussing on elementary processes controlling eye movements in visual search and reading. It investigates the question of how scanning behavior in a letter search task adjusts to changes in spatial visibility created by different visual factors, such as viewing distance, inter-letter spacing and target-background similarity. Each of the three visual factors is found to affect scanning behavior in a different way, either by changing its spatial parameter (saccade size) or its temporal (fixation duration), or both of them at the same time. Possible mechanisms underlying these effects are discussed.

Eye-movement parameters and pattern discrimination

Pattern discrimination was studied in a visual-search task by recordingan O’s eye movements while he determined how many of eight patterns, arranged in a square around a standardpattern, matched the standard pattern. The results demonstrate the role of eye movements in visual search and human pattern discrimination. The mean duration of an eye fixation on a pattern, the probability of fixating it, the probability ofrefixating it, and the sequence in which patterns were fixated were all systematically related to various pattern measures. Multivariateanalyses showed modest correlations between the duration of individual eye fixations and various pattern measures. Relative characteristics of patterns influenced performance more than absolute characteristics of patterns. Patterns that matched a standard were fixated more often and longer than patterns that did not match a standard. The order in which patterns were fixated depended upon their relative characteristics. The results were consistent with a model ofpattern discrimination consistingoftwo stagesin which (1) features of a fixated pattern are abstracted and encoded, and (2) these features are then compared with the features ofanother pattern.