We identify two aspects of the problem of maintaining perceptual stability despite an observer's eye movements. The first, visual direction constancy, is the (egocentric) stability of apparent positions of objects in the visual world relative to the perceiver. The second, visual position constancy, is the (exocentric) stability of positions of objects relative to each other. We analyze the constancy of visual direction despite saccadic eye movements.Three information sources have been proposed to enable the visual system to achieve (...) stability: the structure of the visual field, proprioceptive inflow, and a copy of neural efference or outflow to the extraocular muscles. None of these sources by itself provides adequate information to achieve visual direction constancy; present evidence indicates that all three are used.Our final question concerns how information processing operations result in a stable world. The three traditionally suggested means have been elimination, translation, or evaluation. All are rejected. From a review of the physiological and psychological evidence we conclude that no subtraction, compensation, or evaluation need take place. The problem for which these solutions were developed turns out to be a false one. We propose a “calibration” solution: correct spatiotopic positions are calculated anew for each fixation. Inflow, outflow, and retinal sources are used in this calculation: saccadic suppression of displacement bridges the errors between these sources and the actual extent of movement. (shrink)

People often make use of a spatial “mental time line” to represent events in time. We investigated whether the eyes follow such a mental time line during online language comprehension of sentences that refer to the past, present, and future. Participants' eye movements were measured on a blank screen while they listened to these sentences. Saccade direction revealed that the future is mapped higher up in space than the past. Moreover, fewer saccades were made when two events are simultaneously (...) taking place at the present moment compared to two events that are happening in different points in time. This is the first evidence that oculomotor correlates reflect mental looking along an abstract invisible time line during online language comprehension about time. Our results support the idea that observing eye movements is likely to “detect” invisible spatial scaffoldings which are involved in cognitively processing abstract meaning, even when the abstract meaning lacks an explicit spatial correlate. Theoretical implications of these findings are discussed. (shrink)

When we read narrative texts such as novels and newspaper articles, we segment information presented in such texts into discrete events, with distinct boundaries between those events. But do our eyes reflect this event structure while reading? This study examines whether eye movements during the reading of discourse reveal how readers respond online to event structure. Participants read narrative passages as we monitored their eye movements. Several measures revealed that event structure predicted eye movements. In two experiments, (...) we found that both early and overall reading times were longer for event boundaries. We also found that regressive saccades were more likely to land on event boundaries, but that readers were less likely to regress out of an event boundary. Experiment 2 also demonstrated that tracking event structure carries a working memory load. Eye movements provide a rich set of online data to test the cognitive reality of event segmentation during reading. (shrink)

Background: Neurotypical young adults show task-based modulation and stability of their eye movements across tasks. This study aimed to determine whether persons with aphasia (PWA) modulate their eye movements and show stability across tasks similarly to control participants. Methods: Forty-eight PWA and age-matched control participants completed four eye-tracking tasks: scene search, scene memorization, text-reading, and pseudo-reading. Results: Main effects of task emerged for mean fixation duration, saccade amplitude, and standard deviations of each, demonstrating task-based modulation of eye (...) class='Hi'>movements. Group by task interactions indicated that PWA produced shorter fixations relative to controls. This effect was most pronounced for scene memorization and for individuals who recently suffered a stroke. PWA produced longer fixations, shorter saccades, and less variable eye movements in reading tasks compared to controls. Three-way interactions of group, aphasia subtype, and task also emerged. Text-reading and scene memorization were particularly effective at distinguishing aphasia subtype. Persons with anomic aphasia showed a reduction in reading saccade amplitudes relative to their respective control group and other PWA. Persons with conduction/Wernicke’s aphasia produced shorter scene memorization fixations relative to controls or PWA of other subtypes, suggesting a memorization specific effect. Positive correlations across most tasks emerged for fixation duration and did not significantly differ between controls and PWA. Conclusions: PWA generally produced shorter fixations and smaller saccades relative to controls particularly in scene memorization and text-reading respectively. The effect was most pronounced recently after a stroke. Selectively in reading tasks, PWA produced longer fixations and shorter saccades relative to controls, consistent with reading difficulty. PWA showed task-based modulation of eye movements, though the pattern of results was somewhat abnormal relative to controls. All subtypes of PWA also demonstrated task-based modulation of eye movements. However, persons with anomic aphasia showed reduced modulation of saccade amplitude and smaller reading saccades, possibly to improve reading comprehension. Controls and PWA generally produced stabile fixation durations across tasks and did not differ in their relationship across tasks. Overall, these results suggest there is potential to differentiate among PWA with varying subtypes and from controls using eye movement measures of task-based modulation, especially reading and scene memorization tasks. (shrink)

E-Z Reader achieves an impressive fit of empirical eye movement data by simulating core processes of reading in a computational approach that includes serial word processing, shifts of attention, and temporal overlap in the programming of saccades. However, when common assumptions for the time requirements of these processes are taken into account, severe constraints on the time line within which these elements can be combined become obvious. We argue that it appears difficult to accommodate these processes within a largely sequential (...) modeling framework such as E-Z Reader. (shrink)

The issues the commentators have raised and which we address, include: the debate over how attention is allocated during reading; our distinction between early and late stages of lexical processing; our assumptions about saccadic programming; the determinants of skipping and refixations; and the role that higher-level linguistic processing may play in influencing eye movements during reading. In addition, we provide a discussion of model development and principles for evaluating and comparing models. Although we acknowledge that E-Z Reader is (...) incomplete, we maintain that it provides a good framework for systematically trying to understand how the cognitive, perceptual, and motor systems influence the eyes during reading. (shrink)

Numerous studies have focused on the understanding of rapid automatized naming, which can be applied to predict reading abilities and developmental dyslexia in children. Eye tracking technique, characterizing the essential ocular activities, might have the feasibility to reveal the visual and cognitive features of RAN. However, traditional measures of eye movements ignore many dynamical details about the visual and cognitive processing of RAN, and are usually associated with the duration of time spent on some particular areas of interest, fixation (...) counts, revisited fixation counts, saccadic velocities, or saccadic amplitudes. To cope with this drawback, we suggested an entropy-based method to measure eye movements for the first time, which first mapped eye movements during RAN in a time-series and then analyzed the time-series by a proper definition of entropy from the perspective of information theory. Our findings showed that the entropy was more sensitive to reflect small perturbation of eye movements, and thus gained better performance than traditional measures. We also verified that the entropy of eye movements significantly deceased with the age and the task complexity of RAN, and significantly correlated with traditional eye-movement measures [e.g., total time of naming ] and the RAN-related skills [e.g., selective attention, cognitive speed, and visual-motor integration]. Our findings may bring some new insights into the understanding of both RAN and eye tracking technique itself. (shrink)

The E-Z Reader model (Reichle et al. 1998; 1999) provides a theoretical framework for understanding how word identification, visual processing, attention, and oculomotor control jointly determine when and where the eyes move during reading. In this article, we first review what is known about eye movements during reading. Then we provide an updated version of the model (E-Z Reader 7) and describe how it accounts for basic findings about eye movement control in reading. We then review several alternative models (...) of eye movement control in reading, discussing both their core assumptions and their theoretical scope. On the basis of this discussion, we conclude that E-Z Reader provides the most comprehensive account of eye movement control during reading. Finally, we provide a brief overview of what is known about the neural systems that support the various components of reading, and suggest how the cognitive constructs of our model might map onto this neural architecture. Key Words: attention; eye-movement control; E-Z Reader; fixations; lexical access; models; reading; regressions; saccades. (shrink)

We explore the idea that eye-movement strategies in reading are precisely adapted to the joint constraints of task structure, task payoff, and processing architecture. We present a model of saccadic control that separates a parametric control policy space from a parametric machine architecture, the latter based on a small set of assumptions derived from research on eye movements in reading (Engbert, Nuthmann, Richter, & Kliegl, 2005; Reichle, Warren, & McConnell, 2009). The eye-control model is embedded in a decision (...) architecture (a machine and policy space) that is capable of performing a simple linguistic task integrating information across saccades. Model predictions are derived by jointly optimizing the control of eye movements and task decisions under payoffs that quantitatively express different desired speed-accuracy trade-offs. The model yields distinct eye-movement predictions for the same task under different payoffs, including single-fixation durations, frequency effects, accuracy effects, and list position effects, and their modulation by task payoff. The predictions are compared to—and found to accord with—eye-movement data obtained from human participants performing the same task under the same payoffs, but they are found not to accord as well when the assumptions concerning payoff optimization and processing architecture are varied. These results extend work on rational analysis of oculomotor control and adaptation of reading strategy (Bicknell & Levy, ; McConkie, Rayner, & Wilson, 1973; Norris, 2009; Wotschack, 2009) by providing evidence for adaptation at low levels of saccadic control that is shaped by quantitatively varying task demands and the dynamics of processing architecture. (shrink)

Involuntary eye movement during gaze fixation, referred to as fixational eye movement, consists of two types of components: a Brownian motion like component called drifts-tremor and a ballistic component called microsaccade with a mean saccadic amplitude of about 0.3° and a mean inter-MS interval of about 0.5 s. During GZ fixation in healthy people in an eccentric position, typically with an eccentricity more than 30°, eyes exhibit oscillatory movements alternating between centripetal drift and centrifugal saccade with a mean (...) saccadic amplitude of about 1° and a period in the range of 0.5–1.0 s, which has been known as the physiological gaze-evoked nystagmus. Here, we designed a simple experimental paradigm of GZ fixation on a target shifted horizontally from the front-facing position with fewer eccentricities. We found a clear tendency of centripetal DRT and centrifugal MS as in GEN, but with more stochasticity and with slower drift velocity compared to GEN, even during FEM at GZ positions with small eccentricities. Our results showed that the target shift-dependent balance between DRT and MS achieves the GZ bounded around each of the given targets. In other words, GZ relaxes slowly with the centripetal DRT toward the front-facing position during inter-MS intervals, as if there always exists a quasi-stable equilibrium posture in the front-facing position, and MS actions pull GZ intermittently back to the target position in the opposite direction to DRT. (shrink)

How important is the ability to freely control eye movements for reading comprehension? And how does the parser make use of this freedom? We investigated these questions using coregistration of eye movements and event‐related brain potentials (ERPs) while participants read either freely or in a computer‐controlled word‐by‐word format (also known as RSVP). Word‐by‐word presentation and natural reading both elicited qualitatively similar ERP effects in response to syntactic and semantic violations (N400 and P600 effects). Comprehension was better in free (...) reading but only in trials in which the eyes regressed to previous material upon encountering the anomaly. A more fine‐grained ERP analysis revealed that these regressions were strongly associated with the well‐known P600 effect. In trials without regressions, we instead found sustained centro‐parietal negativities starting at around 320 ms post‐onset; however, these negativities were only found when the violation occurred in sentence‐final position. Taken together, these results suggest that the sentence processing system engages in strategic choices: In response to words that don't match built‐up expectations, it can either explore alternative interpretations (reflected by regressions, P600 effects, and good comprehension) or pursue a “good‐enough” processing strategy that tolerates a deficient interpretation (reflected by progressive saccades, sustained negativities, and relatively poor comprehension). (shrink)

Reichle et al. argue that the mechanism that determines where to fixate the eyes is controlled mostly by low-level processes. Therefore, unlike other competing models (e.g., the SWIFT model), the E-Z Reader model cannot account for “global” regressions as a result of linguistic difficulties. We argue that the model needs to be extended to account for regressive saccades.

The role of titles in perception of visual art is a topic of interesting discussions that brings together artists, curators, and researchers. Titles provide contextual cues and guide perception. They can be particularly useful when paintings include semantic violations that make them challenging for viewers, especially viewers lacking expert knowledge. The aim of this study is to investigate the effects of titles and semantic violations on eye movements. A total of 127 participants without expertise in visual art viewed 40 (...) paintings with and without semantic violations in one of three conditions: untitled, consistent titles and inconsistent titles. After each painting was viewed participants also rated liking and understanding. Our results suggest that titles affect the way paintings are viewed: both titled conditions were associated with shorter first fixation duration, longer saccade durations, and amplitudes and higher dynamic entropy than the untitled conditions. Titles were fixated on more frequently when presented alongside paintings with semantic violations than paintings without violations, and the percentage of fixations to titles was particularly high in the case of paintings with double inconsistencies. Also, we found that semantic violations attracted attention early on, whereas titles received attention later and inconsistencies in titles were processed even later. Finally, semantic violations were associated with higher dynamic entropy than paintings without violations. Our results demonstrate the importance of titles for processing of artworks, especially artworks that present a challenge for the viewers. (shrink)

In order to solve the problem of unsmooth and inefficient human-computer interaction process in the information age, a method for human-computer interaction intention prediction based on electroencephalograph signals and eye movement signals is proposed. This approach is different from previous methods where researchers predict using data from human-computer interaction and a single physiological signal. This method uses the eye movements and EEG signals that clearly characterized the interaction intention as the prediction basis. In addition, this approach is not only (...) tested with multiple human-computer interaction intentions, but also takes into account the operator in different cognitive states. The experimental results show that this method has some advantages over the methods proposed by other researchers. In Experiment 1, using the eye movement signal fixation point abscissa Position X, fixation point ordinate Position Y, and saccade amplitude to judge the interaction intention, the accuracy reached 92%, In experiment 2, only relying on the pupil diameter, pupil size and fixed time, fixed time of eye movement signals can not achieve higher accuracy of the operator’s cognitive state, so EEG signals are added. The cognitive state was identified separately by combining the screened EEG parameters Rα/β with the eye movement signal pupil diameter and fixation time, with an accuracy of 91.67%. The experimental combination of eye movement and EEG signal features can be used to predict the operator’s interaction intention and cognitive state. (shrink)

The book provides a comprehensive state-of-the-art overview of current research on cognitive and applied aspects of eye movements. The contents include peer-reviewed chapters based on a selection of papers presented at the 11th European Conference on Eye Movements (Turku, Finland 2001), supplemented by invited contributions. The ECEM conference series brings together researchers from various disciplines with an interest to use eye-tracking to study perceptual and higher order cognitive functions. The contents of the book faithfully reflect the scope and (...) diversity of interest in eye-tracking as a fruitful tool both in basic and applied research. It consists of five sections: visual information processing and saccadic eye movements; empirical studies of reading and language production; computational models of eye movements in reading; eye-tracking as a tool to study human-computer interaction; and eye movement applications in media and communication research. Each section is concluded by a commentary chapter by one of the leading authorities in the field. These commentaries discuss and integrate the contributions in the section and provide an expert view on the most significant present and future developments in the respective areas. The book is a reference volume including a large body of new empirical work but also principal theoretical viewpoints of leading research groups in the field. (shrink)

Saccadic eye movements create (at least) two related but distinct problems for the visual system: they cause rapid image motion and a displacement of the retinal image. Although it is often assumed that the motion is too fast to be resolved, this is certainly not the case for low-spatial-frequency images. Recent experiments have suggested that the reason we are unaware of the motion during saccades is because motion channels are selectively suppressed, possibly by suppression of the magno-cellular (but (...) not the parvocellular) pathway. This suppression may explain why there is no sensation of motion during saccades, but it leaves open the problem of perceiving a stable world despite continual image displacements. (shrink)

Experiments in animal models have shown that running increases neuronal activity in early visual areas in light as well as in darkness. This suggests that visual processing is influenced by locomotion independent of visual input. Combining mobile electroencephalography, motion- and eye-tracking, we investigated the influence of overground free walking on cortical alpha activity and eye movements in healthy humans. Alpha activity has been considered a valuable marker of inhibition of sensory processing and shown to negatively correlate with neuronal firing (...) rates. We found that walking led to a decrease in alpha activity over occipital cortex compared to standing. This decrease was present during walking in darkness as well as during light. Importantly, eye movements could not explain the change in alpha activity. Nevertheless, we found that walking and eye related movements were linked. While the blink rate increased with increasing walking speed independent of light or darkness, saccade rate was only significantly linked to walking speed in the light. Pupil size, on the other hand, was larger during darkness than during light, but only showed a modulation by walking in darkness. Analyzing the effect of walking with respect to the stride cycle, we further found that blinks and saccades preferentially occurred during the double support phase of walking. Alpha power, as shown previously, was lower during the swing phase than during the double support phase. We however could exclude the possibility that the alpha modulation was introduced by a walking movement induced change in electrode impedance. Overall, our work indicates that the human visual system is influenced by the current locomotion state of the body. This influence affects eye movement pattern as well as neuronal activity in sensory areas and might form part of an implicit strategy to optimally extract sensory information during locomotion. (shrink)

Eye-tracking is increasingly studied as a cognitive and biological marker for the early signs of neuropsychological and psychiatric disorders. However, in order to make further progress, a more comprehensive understanding of the age-related effects on eye-tracking is essential. The antisaccade task requires participants to make saccadic eye movements away from a prepotent stimulus. Speculation on the cause of the observed age-related differences in the antisaccade task largely centers around two sources of cognitive dysfunction: inhibitory control (IC) and working (...) memory (WM). The IC account views cognitive slowing and task errors as a direct result of the decline of inhibitory cognitive mechanisms. An alternative theory considers that a deterioration of WM is the cause of these age-related effects on behavior. The current study assessed IC and WM processes underpinning saccadic eye movements in young and older participants. This was achieved with three experimental conditions that systematically varied the extent to which WM and IC were taxed in the antisaccade task: a memory-guided task was used to explore the effect of increasing the WM load; a Go/No-Go task was used to explore the effect of increasing the inhibitory load; a ‘standard’ antisaccade task retained the standard WM and inhibitory loads. Saccadic eye movements were also examined in a control condition: the standard prosaccade task where the load of WM and IC were minimal or absent. Saccade latencies, error rates and the spatial accuracy of saccades of older participants were compared to the same measures in healthy young controls across the conditions. The results revealed that aging is associated with changes in both IC and WM. Increasing the inhibitory load was associated with increased reaction times in the older group, while the increased WM load and the inhibitory load contributed to an increase in the antisaccade errors. These results reveal that aging is associated with changes in both IC and WM. (shrink)

This commentary focuses on Findlay & Walker's model and more specifically, on its underestimation of the role of cognitive processes in eye movement control during complex activities such as text scanning. In particular, the issue of the complexity of the subject's task/behavior is discussed to stress the importance of the link between selection for perceptual processing on the one hand, and the selection of a target for a saccade, on the other. Future models will have to account for the fact (...) that the goal of any saccade is to bring the eyes to a relevant object and that the selection of this saccade target is closely related to object recognition. (shrink)

Reichle et al. specify two assumptions as being basic to E-Z Reader: Words are sequentially attended during fixations, and saccades are triggered by a cognitive event. We point out that there is little evidence for the first assumption and counterevidence for the second. Also, the labile/nonlabile stage distinction in saccade preparation seems to be contrary to current evidence. An alternative explanation of saccade onset times in reading assumes that saccades are strategically generated, independent of language processing, but are delayed on (...) a probabilistic basis by processing difficulties. (shrink)

Microsaccades, small saccadic eye movements occurring during fixation, have been suggested to be modulated by various sensory, cognitive, and affective processes relating to arousal. Although the modulation of fatigue-related arousal on microsaccade behavior has previously been characterized, the influence of other aspects of arousal, such as emotional arousal, is less understood. Moreover, microsaccades are modulated by cognitive processes that could also be linked to arousal. To investigate the influence of emotional arousal, saccade preparation, and global luminance levels on (...) microsaccade behavior, emotional auditory stimuli were presented prior to the onset of a fixation cue whose color indicated to look either at the peripheral stimulus or in the opposite direction of the stimulus. Microsaccade behavior was found to be significantly modulated by saccade preparation and global luminance level, but not emotional arousal. In the pro- and anti-saccade task, microsaccade rate was lower during anti-saccade preparation as compared to pro-saccade preparation, though microsaccade dynamics were comparable during both trial types. Our results reveal a differential role of arousal linked to emotion, fatigue, saccade preparation, and global luminance level on microsaccade behavior. (shrink)

Previous studies have shown that the human visual system can detect a face and elicit a saccadic eye movement toward it very efficiently compared to other categories of visual stimuli. In the first experiment, we tested the influence of facial expressions on fast face detection using a saccadic choice task. Face‐vehicle pairs were simultaneously presented and participants were asked to saccade toward the target (the face or the vehicle). We observed that saccades toward faces were initiated faster, and (...) more often in the correct direction, than saccades toward vehicles, regardless of the facial expressions (happy, fearful, or neutral). We also observed that saccade endpoints on face images were lower when the face was happy and higher when it was neutral. In the second experiment, we explicitly tested the detection of facial expressions. We used a saccadic choice task with emotional‐neutral pairs of faces and participants were asked to saccade toward the emotional (happy or fearful) or the neutral face. Participants were faster when they were asked to saccade toward the emotional face. They also made fewer errors, especially when the emotional face was happy. Using computational modeling, we showed that this happy face advantage can, at least partly, be explained by perceptual factors. Also, saccade endpoints were lower when the target was happy than when it was fearful. Overall, we suggest that there is no automatic prioritization of emotional faces, at least for saccades with short latencies, but that salient local face features can automatically attract attention. (shrink)

The aim of the present study was to investigate how saccadic selection relates to people’s awareness of the saliency and identity of a saccade goal. Observers were instructed to make an eye movement to either the most salient line segment or the only right-tilted element in a visual search display. The display was masked contingent on the first eye movement and after each trial observers indicated whether or not they had correctly selected the target. Whereas people’s awareness concerning the (...) saliency of the saccade goal was generally low, their awareness concerning the identity was high. Observers’ awareness of the saccade goal was not related to saccadic performance. Whereas saccadic selection consistently varied as a function of saccade latency, people’s awareness concerning the saliency or identity of the saccade goal did not. The results suggest that saccadic selection is primarily driven by subconscious processes. (shrink)

Synchronized movements with external periodic rhythms, such as dancing to a beat, are commonly observed in daily life. Although it has been well established that some vocal learning species (including parrots and humans) spontaneously develop this ability, it has only recently been shown that monkeys are also capable of predictive and tempo-flexible synchronization to periodic stimuli. In our previous study, monkeys were trained to make predictive saccades for alternately presented visual stimuli at fixed stimulus onset asynchronies (SOAs) to obtain (...) a liquid reward. The monkeys generalized predictive synchronization to novel SOAs in the middle of trained range, suggesting a capacity for tempo-flexible synchronization. However, it is possible that when encountering a novel tempo, the monkeys might sample learned saccade sequences from those for the short and long SOAs so that the mean saccade interval matched the untrained SOA. To eliminate this possibility, in the current study we tested monkeys on novel SOAs outside the trained range. Animals were trained to generate synchronized eye movements for 600 and 900-ms SOAs for a few weeks, and then were tested for longer SOAs. The accuracy and precision of predictive saccades for one untrained SOA (1200 ms) were comparable to those for the trained conditions. On the other hand, the variance of predictive saccade latency and the proportion of reactive saccades increased significantly in the longer SOA conditions (1800 and 2400 ms), indicating that temporal prediction of periodic stimuli was difficult in this range, similar to previous results on synchronized tapping in humans. Our results suggest that monkeys might share similar synchronization mechanisms with humans, which can be subject to physiological examination in future studies. (shrink)

Our target article discussed how emerging knowledge of the physiological processes involved in the control of saccadic eye movements provided the basis for a functional framework in which to understand the programming of such movements. The commentators raised many interesting issues in their varied responses that ranged from detailed discussion of the physiological substrate through issues of saccade control in reading. New evidence at the physiological level demonstrates that some elaborations are needed to the framework we proposed. (...) Most clearly, the spatial selection process operates in a manner different from our suggestion of an increase in activity in the salience map. Some commentators make the interesting and welcome proposal that the functional processes we outline may in fact be implemented with an even more unified physiological substrate (continuity between collicular fixation and build-up cells) than we envisaged. Extensions to the framework are discussed involving the planning of sequential saccades, saccades made in crossmodal situations, the influences of learning and memory, and binocular saccades. We consider carefully the commentaries proposing explicit attentional and/or executive processes in the programming of saccades. We integrate the comments of researchers investigating saccade control in neurological and neuropsychiatric patients and finally discuss whether the framework can account for saccades made in the course of reading. (shrink)

Color coding is used to guide attention in computer displays for such critical tasks as baggage screening or air traffic control. It has been shown that a display object attracts more attention if its color is more similar to the color for which one is searching. However, what does similar precisely mean? Can we predict the amount of attention that a display color will receive during a search for a given target color? To tackle this question, two color‐search experiments measuring (...) the selectivity of saccadic eye movements and mapping out its underlying color space were conducted. A variety of mathematical models, predicting saccadic selectivity for given target and display colors, were devised and evaluated. The results suggest that applying a Gaussian function to a weighted Euclidean distance in a slightly modified HSI color space is the best predictor of saccadic selectivity in the chosen paradigm. Hue and intensity information by itself provides a basis for useful predictors, spanning a possibly spherical color space of saccadic selectivity. Although the current models cannot predict saccadic selectivity values for a wide variety of visual search tasks, they reveal some characteristics of color search that are of both theoretical and applied interest, such as for the design of human–computer interfaces. (shrink)