EyeLink Cognitive Publications
All EyeLink cognitive and perception research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Visual Search, Scene Perception, Face Processing, etc. You can also search for individual author names. If we missed any EyeLink cognitive or perception articles, please email us!
2002 |
Timothy L. Hodgson; Dominic J. Mort; M. M. Chamberlain; Samuel B. Hutton; K. S. O'Neill; Christopher Kennard Orbitofrontal cortex mediates inhibition of return Journal Article In: Neuropsychologia, vol. 40, no. 12, pp. 1891–1901, 2002. @article{Hodgson2002, Recent accounts have proposed that orbitofrontal cerebral cortex mediates the control of behavior based on emotional feedback and its somatic correlates. Here, we describe the performance of a patient with circumscribed damage to orbitofrontal cortex during a task that requires switching between sensory-motor mappings, contingent on the occurrence of positive and negative reward feedbacks. In this test, normal subjects and other patients with prefrontal damage show an increase in latencies for eye movements towards locations at which a negative feedback was presented on the preceding trial. In contrast, our patient does not show this reward-dependent inhibition of return effect on saccades. She was also found to make an increased rate of ocular refixations during visual search and used a disorganized search strategy in a token foraging task. These findings suggest that orbital regions of the prefrontal cortex mediate an inhibitory effect on actions directed towards locations that have been subject to negative reinforcement. Further, this mechanism seems to play a role in controlling natural search and foraging behavior. |
Amelia R. Hunt; Raymond M. Klein Eliminating the cost of task set reconfiguration Journal Article In: Memory & Cognition, vol. 30, no. 4, pp. 529–539, 2002. @article{Hunt2002, With insufficient time to fully prepare for a switch in task, a deterioration in performance on the first trial of a new task would be expected. The interest of researchers has been captured by the residual switch costs that, surprisingly, remain despite sufficient time to prepare. We used avery simple task to investigate the costs to reaction time and accuracy associated with changing between two different instructional sets every eight trials. Subjects responded to left and right visual targets by making either spatially compatible or incompatible eye movements (Experiment 1) or buttonpress responses (Experiment 2). The subjects were cued as to whether to make the compatible or the incompatible response by the color of a border appearing on the perimeter of the display. In cases in which the subject alternated between making pro- and antisaccades, the large costs to reaction time and accuracy at the short cue-target stimulus onset asynchrony were completely eliminated when sufficient time was provided to prepare for the switch. This complete elimination of residual switch costs was not obtained when the same alternation was applied to manual responses. This pattern of results links residual costs to response selection processes and suggests that they are not a necessary component of the switch process. We propose that the elimination of "stubborn" residual switch costs is rooted in our use of a hypercompatible task (making saccades toward targets) that places minimal demands on response selection. |
Chiang-Shan Ray Li; Shih Chieh Lin A perceptual level mechanism of the inhibition of return in oculomotor planning Journal Article In: Cognitive Brain Research, vol. 14, no. 2, pp. 269–276, 2002. @article{Li2002, A motor response to a visual target presented at a precued spatial location is facilitated if the target is presented shortly after the cue and inhibited when the cue target onset asynchrony approaches a few hundred milliseconds. The latter effect is termed inhibition of return (IOR). It is suggested that IOR provides an important strategy for effective search in our visual environment. Despite studies demonstrating IOR in a number of behavioral tasks, its neural mechanism has remained elusive. As a fundamental step toward understanding these mechanisms, the current study examines whether IOR mainly involves a perceptual or a motor process. We conducted a series of experiments, in which the target instructed saccades to the cued or to a different location. In each experiment, we observed a similar pattern of IOR when the target followed the cue, but not when the saccade was directed to the cued location. In another two experiments, we demonstrated that the magnitude and temporal profile of IOR varied depending on whether an eye movement or a manual response was involved. Overall, the present study suggests that IOR results predominantly from a perceptual level mechanism, with its magnitude and time course modulated by the activation of specific motor effectors. We discuss the implications of these results for attention gating of perceptual inputs and for mechanisms of visuomotor control. |
Chiang-Shan Ray Li; Shih Chieh Lin Inhibition of return in temporal order saccades Journal Article In: Vision Research, vol. 42, no. 17, pp. 2089–2093, 2002. @article{Li2002a, Inhibition of return (IOR) is an attention mechanism that expedites the search of an object in our environment. Results in different studies support either a perceptual or motor account of IOR. One problem with the perceptual account is that IOR has not been observed in temporal order judgment. Here we demonstrate that IOR can be observed in a temporal order saccade task where eye movement instead of manual response is used to select the target. The result suggests the importance of monitoring eye movement in studies of IOR. |
Harold Bekkering; Sebastiaan F. W. Neggers Visual search is modulated by action intentions Journal Article In: Psychological Science, vol. 13, no. 4, pp. 370–374, 2002. @article{Bekkering2002, The influence of action intentions on visual selection processes was investigated in a visual search paradigm. A predefined target object with a certain orientation and color was presented among distractors, and subjects had to either look and point at the target or look at and grasp the target. Target selection processes prior to the first saccadic eye movement were modulated by the different action intentions. Specifically, fewer saccades to objects with the wrong orientation were made in the grasping condition than in the pointing condition, whereas the number of saccades to an object with the wrong color was the same in the two conditions. Saccadic latencies were similar under the different task conditions, so the results cannot be explained by a speed-accuracy trade-off. The results suggest that a specific action intention, such as grasping, can enhance visual processing of action-relevant features, such as orientation. Together, the findings support the view that visual attention can be best understood as a selection-for-action mechanism. |
Eva Belke; Antje S. Meyer In: European Journal of Cognitive Psychology, vol. 14, no. 2, pp. 237–266, 2002. @article{Belke2002, We investigated the time course of conjunctive ''same''–''different'' judgements for visually presented object pairs by means of combined reaction time and on-line eye movement measurements. The analyses of viewing patterns, viewing times, and reaction times showed that participants engaged in a parallel self-terminating search for differences. In addition, the results obtained for objects differing in only one dimension suggest that processing times may depend on the relative codability of the stimulus dimensions. The results are reviewed in a broader framework in view of higher-order processes. We propose that overspecifications of colour, often found in object descriptions, may have an ''early'' visual rather than a ''late'' linguistic origin. In a parallel assessment of the detection materials, participants overspecified the objects' colour substantially more often than their size. We argue that referential overspecifications of colour are largely attributable to mechanisms of visual discrimination. |
Sebastiaan F. W. Neggers; H. Bekkering Coordinated control of eye and hand movements in dynamic reaching Journal Article In: Human Movement Science, vol. 21, no. 3, pp. 37–64, 2002. @article{Neggers2002, In the present study, we integrated two recent, at first sight contradictory findings regarding the question whether saccadic eye movements can be generated to a newly presented target during an ongoing hand movement. Saccades were measured during so-called adaptive and sustained pointing conditions. In the adapted pointing condition, subjects had to direct both their gaze and arm movements to a displaced target location. The results showed that the eyes could fixate the new target during pointing. In addition, a temporal coupling of these corrective saccades was found with changes in arm movement trajectories when reaching to the new target. In the sustained pointing condition, however, the same subjects had to point to the initial target, while trying to deviate their gaze to a new target that appeared during pointing. It was found that the eyes could not fixate the new target before the hand reached the initial target location. Together, the results indicate that ocular gaze is always forced to follow the target intended by a manual arm movement. A neural mechanism is proposed that couples ocular gaze to the target of an arm movement. Specifically, the mechanism includes a reach neuron layer besides the well-known saccadic layer in the primate superior colliculus. Such a tight, sub-cortical coupling of ocular gaze to the target of a reaching movement can explain the contrasting behavior of the eyes in dependency of whether the eye and hand share the same target position or attempt to move to different locations. |
Jason P. Mitchell; C. Neil MacRae; Iain D. Gilchrist Working memory and the suppression of reflexive saccades Journal Article In: Journal of Cognitive Neuroscience, vol. 14, no. 1, pp. 95–103, 2002. @article{Mitchell2002, Conscious behavioral intentions can frequently fail under conditions of attentional depletion. In attempting to trace the cognitive origin of this effect, we hypothesized that failures of action control–specifically, oculomotor movement–can result from the imposition of fronto-executive load. To evaluate this prediction, participants performed an antisaccade task while simultaneously completing a working-memory task that is known to make variable demands on prefrontal processes (n-back task, see Jonides et al., 1997). The results of two experiments are reported. As expected, antisaccade error rates were increased in accordance with the fronto-executive demands of the n-back task (Experiment 1). In addition, the debilitating effects of working-memory load were restricted to the inhibitory component of the antisaccade task (Experiment 2). These findings corroborate the view that working memory operations play a critical role in the suppression of prepotent behavioral responses. |
Helena Ojanpää; Risto Näsänen; Ilpo Kojo Eye movements in the visual search of word lists Journal Article In: Vision Research, vol. 42, no. 12, pp. 1499–1512, 2002. @article{Ojanpaeae2002, The word identification span refers to the area of the visual field in which words can be identified during a single fixation. The purpose of the study was to estimate the vertical word identification span in a visual word search task, in which words were arranged in a vertical list. In addition, we studied the effect of list layout (orientation, length, and line spacing) on the speed of search and eye movements. The task of the observer was to identify a target word in a word list, where the other words were distracters. Threshold search time, that is, stimulus presentation time for correct identification at a probability level of 0.79, was determined by using a multiple alternative staircase method. Eye movements were recorded simultaneously. The results showed that, in vertical lists, 4-5 words could be identified during a single fixation. Thus, the vertical word identification span was 4-5 character spaces, whereas according to previous studies the horizontal word identification span is about 10 character spaces, which corresponds to 1-2 words. There were fewer fixations and the saccade amplitudes were smaller for vertical than for horizontal lists of the same length. However, search times did not depend on list orientation. This was due to longer fixation times for vertical lists. Further, since average fixation duration for vertical lists was longer than for horizontal lists, processing time seems to depend on the number of items within the span. © 2002 Elsevier Science Ltd. All rights reserved. |
Richard Godijn; Jan Theeuwes Oculomotor capture and Inhibition of Return: Evidence for an oculomotor suppression account of IOR Journal Article In: Psychological Research, vol. 66, no. 4, pp. 234–246, 2002. @article{Godijn2002a, Previous research has shown that when subjects search for a particular target object the sudden appearance of a new object captures the eyes on a large proportion of trials. The present study examined whether the onset affects the oculomotor system even when the eyes move directly towards the target. Ten participants ranging in age from 18-28 yrs served as paid volunteers. Using a modified version of the oculomotor paradigm (see Theeuwes, Kramer, Hahn, & Irwin, 1998) we show that when the eyes moved to the target object, subsequent saccades were inhibited from moving to a location at which a new object had previously appeared (inhibition-of-return; IOR). Whether or not a saccade to the onset was executed had no effect on the size of the inhibition. In particular conditions, the trajectories of saccades to the target objects were slightly curved in the opposite direction of the onset. The data are interpreted in the context of a novel hypothesis regarding oculomotor IOR. |
Richard Godijn; Jan Theeuwes Programming of endogenous and exogenous saccades: Evidence for a competitive integration model Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 28, no. 5, pp. 1039–1054, 2002. @article{Godijn2002b, Participants were required to make a saccade to a uniquely colored target while ignoring the presentation of an onset distractor. The results provide evidence for a competitive integration model of saccade programming that assumes endogenous and exogenous saccades are programmed in a common saccade map. The model incorporates a lateral interaction structure in which saccade-related activation at a specific location spreads to neighboring locations but inhibits distant locations. In addition, there is top-down, location-specific inhibition of locations to which the saccade should not go. The time course of exogenous and endogenous activation in the saccade map can explain a variety of eye movement data, including endpoints, latencies, and trajectories of saccades and the well-known global effect. |
Veerle Gysen; Peter De Graef; Karl Verfaillie Detection of intrasaccadic displacements and depth rotations of moving objects Journal Article In: Vision Research, vol. 42, no. 3, pp. 379–391, 2002. @article{Gysen2002, In a display with a stationary and a moving object, subjects saccaded towards one of the objects and had to detect intrasaccadic changes in position or orientation of either the saccade target or the saccade flanker. Compared to performance for stationary objects, displacement detection for translating objects was better and unaffected by saccadic status of the changed object. This pattern proved to be specific to position changes in translating objects and did not generalize to other types of motion (i.e., rotation) or to other types of intrasaccadic changes (i.e., orientation shifts). Superior transsaccadic coding of the position of a translating object was also observed in control experiments with only a single object present on each trial. Possible accounts in terms of selective attention to moving objects and perceptual relevance of object position are pitted against the data, suggesting qualitative differences in the transsaccadic representation of translating and stationary objects. |
Veerle Gysen; Karl Verfaillie; Peter De Graef The effect of stimulus blanking on the detection of intrasaccadic displacements of translating objects Journal Article In: Vision Research, vol. 42, no. 16, pp. 2021–2030, 2002. @article{Gysen2002a, In a display with a stationary and a translating object, subjects made a saccade towards one of the objects and had to detect intrasaccadic changes in the position of either the saccade target or the saccade flanker. Sensitivity for displacements of the stationary and moving objects was measured in conditions with (60 and 220 ms) and without blanking. In the conditions without blanking, displacement detection for translating objects was better than detection for stationary objects, which confirmed previous results (Vis. Res. 42 (2002) 379). This pattern was reversed in the blanking conditions: Sensitivity for intrasaccadic displacements of the translating object decreased drastically in comparison to conditions without a blank and was even lower than sensitivity for the stationary object. The results suggest differences in the transsaccadic spatial representation of translating and stationary objects. While a change in the spatial position of a stationary object can be detected after a blank period of 60 and 220 ms, this seems impossible for a translating object, indicating timing differences in postsaccadic spatial localization processes. Accounts in terms of a fast and accurate motion processing mechanism that possibly makes use of gain control are discussed. © 2002 Elsevier Science Ltd. All rights reserved. |
Veerle Gysen; Karl Verfaillie; Peter De Graef Transsaccadic perception of translating objects: Effects of landmark objects and visual field position Journal Article In: Vision Research, vol. 42, no. 14, pp. 1785–1796, 2002. @article{Gysen2002b, Previously Gysen, De Graef, and Verfaillie [Vision Research 42 (2002) 379] showed that, with stimulus displays presenting one stationary and one translating object, sensitivity for intrasaccadic displacements was higher for translating than for stationary objects. In the present paper the importance of the relative encoding of the path of the translating object towards the stationary object is investigated. In three experiments we compared detection of intrasaccadic displacements of translating objects in relative motion (moving towards the landmark object) and translating objects moving in isolation. No 'facilitatory' effect of relative motion was found. However a visual field effect was present. Performance was always better for the translating object presented in the lower part in comparison to the upper part of the visual field. A fourth experiment investigated the sensitivity for intrasaccadic displacements of stationary and translating objects presented in the upper as well as in the lower visual field. A lower visual field advantage was observed. The superior performance for translating objects, as was found previously, was confirmed in the lower and upper visual field. |
Martin Greschner; Markus Bongard; Pal Rujan; Josef Ammermüller Retinal ganglion cell synchronization by fixational eye movements improves feature estimation Journal Article In: Nature Neuroscience, vol. 5, no. 4, pp. 341–347, 2002. @article{Greschner2002, Image movements relative to the retina are essential for the visual perception of stationary objects during fixation. Here we have measured fixational eye and head movements of the turtle, and determined their effects on the activity of retinal ganglion cells by simulating the movements on the isolated retina. We show that ganglion cells respond mainly to components of periodic eye movement that have amplitudes of roughly the diameter of a photoreceptor. Drift or small head movements have little effect. Driven cells that are located along contrast borders are synchronized, which reliably signals a preceding movement. In an artificial neural network, the estimation of spatial frequencies for various square wave gratings improves when timelocked to this synchronization. This could potentially improve stimulus feature estimation by the brain. |
Danny Gagnon; Gillian A. O'Driscoll; Michael Petrides; G. B. Pike The effect of spatial and temporal information on saccades and neural activity in oculomotor structures Journal Article In: Brain, vol. 125, no. 1, pp. 123–139, 2002. @article{Gagnon2002, It has been argued that saccade generation is supported by two systems, a'where' system that decides the direction and extent of an impending saccade, and a 'when' system that is involved in the timing of the release of fixation. We evaluated the contributions of these systems to saccade latencies, and used functional MRI to identify the neural substrates of these systems. We found that advance knowledge of the direction and the timing of an impending target movement had both overlapping and discrete effects on saccade latencies and on neural activation. Knowledge of either factor decreased regular saccade latencies. However, knowledge of target direction increased the number of predictive and express saccades while knowledge of target timing did not. The brain activation data showed that advance knowledge of the direction or the timing of the target movement activated primarily overlapping structures. The precentral gyrus, in the region of the frontal eye fields, was more active in conditions in which some aspect of the target movement was predictable than in saccade control and fixation conditions. In the basal ganglia, activation discriminated between advance knowledge of target timing and target direction. The lenticular nuclei were more active when only target timing was known in advance, while the caudate was more active when only target direction was known in advance. These data suggest that the neural structures supporting the 'where' and 'when' systems are highly overlapping, although there is some dissociation sub-cortically. Knowledge of target timing and target direction converge in precentral gyrus, a region where there is strong evidence of context-dependent modulation of neural activity. |
Steven Yantis; Jens Schwarzbach; John T. Serences; Robert L. Carlson; Michael A. Steinmetz; James J. Pekar; Susan M. Courtney Transient neural activity in human parietal cortex during spatial attention shifts Journal Article In: Nature Neuroscience, vol. 5, no. 10, pp. 995–1002, 2002. @article{Yantis2002, Observers viewing a complex visual scene selectively attend to relevant locations or objects and ignore irrelevant ones. Selective attention to an object enhances its neural representation in extrastriate cortex, compared with those of unattended objects, via top-down attentional control signals. The posterior parietal cortex is centrally involved in this control of spatial attention. We examined brain activity during attention shifts using rapid, event-related fMRI of human observers as they covertly shifted attention between two peripheral spatial locations. Activation in extrastriate cortex increased after a shift of attention to the contralateral visual field and remained high during sustained contralateral attention. The time course of activity was substantially different in posterior parietal cortex, where transient increases in activation accompanied shifts of attention in either direction. This result suggests that activation of the parietal cortex is associated with a discrete signal to shift spatial attention, and is not the source of a signal to continuously maintain the current attentive state. |
Boris M. Velichkovsky; Alexandra Rothert; Mathias Kopf; Sascha M. Dornhoefer; Markus Joos Towards an express-diagnostics for level of processing and hazard perception Journal Article In: Transportation Research Part F: Traffic Psychology and Behaviour, vol. 5, no. 2, pp. 145–156, 2002. @article{Velichkovsky2002a, The analysis of eye movements can provide rich information about driver's attention and the course of behaviour in hazardous situations. We present data from a driving simulation study showing that the switching between preattentive and attentive processing is reflected in visual fixations. For this initial analysis, we considered fixations from the perspective of their duration and the amplitude of related saccades. Since fixation durations may change instantaneously from one fixation to the next, we further selected the temporal vicinity of the emerging hazard for a closer analysis of fixations around this time. With this second type of analysis, the fixations that actually "detect" a critical event can be discovered and their duration measured. Upon detection of an immediate hazard, there is an increase in fixation duration and a corresponding increase in occurrence of attentive fixations on the cost of preattentive ones. This switching from one level of processing to another is recognisable on a short, phasic time scale. We finally discuss attentional conditions where overlooked or not sufficiently processed hazards do not lead to the appropriate breaking reaction on the part of the driver. |
Jason S. Carley; Arthur F. Kramer; Matthew S. Peterson Overt and covert object based attention Journal Article In: Psychonomic Bulletin & Review, vol. 9, no. 4, pp. 751–758, 2002. @article{Carley2002, To examine the role of perceptual object representations in the control of eye movements and attention, a pair of experiments adapted the object-cuing paradigm of Egly, Driver, and Rafal (1994) to require eye movements. Displays were pairs of adjacent rectangles, each containing two characters. Observers were asked to make a speeded judgment of a target character's orientation, and a cue was provided prior to target/distractor onset to indicate the target's likely location. Gaze-contingent presentation of target and distractors was used to demand overt scanning of displays. Eye movements during task perfor- mance evinced two forms of object-based effects. First, saccades following fixation on an invalidly cued item were more likely to be made within the cued rectangle than between rectangles. Second, sac- cades within the cued rectangle were preceded by shorter dwell times than saccades between rectan- gles. Extrafoveal processing of stimuli within the cued rectangle, however, was not facilitated, suggest- ing that covert attention was not allocated more densely within the cued than within the uncued object. |
Emanuela Bricolo; Tiziana Gianesini; Alessandra Fanini; Claus Bundesen; Leonardo Chelazzi Serial attention mechanisms in visual search: A direct behavioral demonstration Journal Article In: Journal of Cognitive Neuroscience, vol. 14, no. 7, pp. 980–993, 2002. @article{Bricolo2002, In visual search, inefficient performance of human observers is typically characterized by a steady increase in reaction time with the number of array elements-the so-called set-size effect. In general, set-size effects are taken to indicate that processing of the array elements depends on limited-capacity resources, that is, it involves attention. Contrasting theories have been proposed to account for this attentional involvement, however. While some theories have attributed set-size effects to the intervention of serial attention mechanisms, others have explained set-size effects in terms of parallel, competitive architectures. Conclusive evidence in favor of one or the other notion is still lacking. Especially in view of the wide use of visual search paradigms to explore the functional neuroanatomy of attentional mechanisms in the primate brain, it becomes essential that the nature of the attentional involvement in these paradigms be clearly defined at the behavioral level. Here we report a series of experiments showing that highly inefficient search indeed recruits serial attention deployment to the individual array elements. In addition, we describe a number of behavioral signatures of serial attention in visual search that can be used in future investigations to attest a similar involvement of serial attention in other search paradigms. We claim that only after having recognized these signatures can one be confident that truly serial mechanisms are engaged in a given visual search task, thus making it amenable for exploring the functional neuroanatomy underlying its performance. |
Tanja R. M. Coeckelbergh The effect of visual field defects on driving performance Journal Article In: Archives of Ophthalmology, vol. 120, no. 11, pp. 1509–1516, 2002. @article{Coeckelbergh2002a, Objectives: To investigate the effect of visual field de-fects on driving performance, and to predict practical fit-ness to drive. Methods: The driving performance of 87 subjects with visual field defects due to ocular abnormalities was as-sessed on a driving simulator and during an on-road driv-ing test. Outcome Measures: The final score on the on-road driving test and simulator indexes, such as driving speed, viewing behavior, lateral position, time-headway, and time to collision. Results: Subjects with visual field defects showed dif-ferential performance on measures of driving speed, steer-ing stability, lateral position, time to collision, and time-headway. Effective compensation consisted of reduced driving speed in cases of central visual field defects and increased scanning in cases of peripheral visual field de-fects. The sensitivity and specificity of models based on vision, visual attention, and compensatory viewing effi-ciency were increased when the distance at which the sub-ject started to scan was taken into account. Conclusions: Subjects with visual field defects demon-strated differential performance on several driving simu-lator indexes. Driving examiners considered reduced speed and increased scanning to be valid compensation for cen-tral and peripheral visual field defects, respectively. Pre-dicting practical fitness to drive was improved by taking driving simulator indexes into account. |
Lana Dépatie; Gillian A. O'Driscoll; Anne Lise V. Holahan; Victoria Atkinson; Joseph X. Thavundayil; N. Ng Ying Kin; Samarthji Lal Nicotine and behavioral markers of risk for schizophrenia: A double-blind, placebo-controlled, cross-over study Journal Article In: Neuropsychopharmacology, vol. 27, no. 6, pp. 1056–1070, 2002. @article{Depatie2002, We investigated the effect of nicotine on three behavioral markers of risk for schizophrenia: sustained attention (using the Continuous Performance Task (CPT)), antisaccade performance, and smooth pursuit. Smooth pursuit was investigated in two conditions, one in which attention was enhanced (monitoring target changes) and one in which attention was not enhanced (no monitoring). Patients with schizophrenia (n = 15) and controls (n = 14) were given a 14-mg nicotine patch in a double-blind, placebo-controlled, crossover design and plasma nicotine concentrations were monitored. Nicotine concentrations were similar in both groups. A Group X Drug interaction (p < .02) on CPT hits indicated that nicotine improved sustained attention in patients but not in controls. Nicotine significantly decreased antisaccade errors (p < .01) in both groups. A Drug X Monitoring condition interaction (p < .01) on pursuit gain indicated that nicotine significantly increased pursuit gain in the no-monitoring condition in patients and controls equally, but did not improve pursuit in the monitoring condition. Thus, improvement in pursuit may have been mediated via an effect on attention rather than by an effect on oculomotor function per se. In patients, the magnitude of improvement in attention on nicotine was correlated with the improvement on eye movement tasks. Thus, nicotine improves performance on both attention and oculomotor markers of risk for schizophrenia, possibly via common mechanisms. |
Matthew S. Peterson; Arthur F. Kramer; David E. Irwin; Sowon Hahn Modulation of oculomotor capture by abrupt onsets during attentionally demanding visual search Journal Article In: Visual Cognition, vol. 9, no. 6, pp. 755–791, 2002. @article{Peterson2002, The influence of abrupt onsets on attentionally demanding visual search (i.e., search for a letter target among heterogeneous letter distractors), as indexed by performance and eye movement measures, was investigated in a series of studies. In Experiments 1 and 2 we examined whether onsets would capture the eyes when the appearance of an onset predicted neither the location nor the identity of the target. Subjects did direct their eyes to the abrupt onsets on a disproportionate number of trials in these studies. Interestingly, however, onset capture was modulated by subjects' scan strategies. Furthermore, onsets captured the eyes less frequently than would have been predicted by paradigms showing attentional capture when no eye movements are required. Experiment 3 examined the question of whether onsets would capture the eyes in a situation in which they never served as the target. Capture was observed in this study. However, the magnitude of capture effects was substantially diminished as compared to previous behavioural studies in which the onset had a chance probability of serving as the target. These data are discussed in terms of the influence of top-down constraints on stimulus-driven attentional and oculomotor capture by abrupt onset stimuli. |
Casimir J. H. Ludwig; Iain D. Gilchrist Stimulus-driven and goal-driven control over visual selection Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 28, no. 4, pp. 902–912, 2002. @article{Ludwig2002a, This article explored the extent to which stimulus-driven control over visual selection is modulated by goal-driven factors. Observers searched for a no-onset color target among 3 distractors and signaled its location either manually or with a saccade. Additional distractors appeared either with or without an abrupt onset and were either similar or dissimilar to the target. Abrupt onsets disrupted saccades to the target, especially when they shared the target color. Irrelevant onsets also interfered with the manual responses, but this interference was dependent on the particular type of manual response. Stimulus-driven and contingent capture can occur within a single paradigm, but the extent and nature of these effects depend on the specific response required. |
2001 |
Matthew S. Peterson; Arthur F. Kramer Attentional guidance of the eyes by contextual information and abrupt onsets Journal Article In: Perception and Psychophysics, vol. 63, no. 7, pp. 1239–1249, 2001. @article{Peterson2001a, Contextual cuing is a memory-based phenomenon in which previously encountered global pattern information in a display can automatically guide attention to the location of a target (Chun & Jiang, 1998), leading to rapid and accurate responses. What is not clear is how contextual cuing works. By monitoring eye movements, we investigated the roles that recognition and guidance play in contextual cuing. Recognition does not appear to occur on every trial and sometimes does not have its effects until later in the search process. When recognition does occur, attention is guided straight to the target rather than in the general direction. In Experiment 2, we investigated the interaction between memory-driven search (contextual cuing) and stimulus-driven attentional capture by abrupt onsets. Contextual cuing was able to override capture by abrupt onsets. In contrast, onsets had almost no effect on the degree of contextual cuing. These data are discussed in terms of the role of top-down and bottom-up factors in the guidance of attention in visual search. |
Matthew S. Peterson; Arthur F. Kramer; Ranxiao Frances Wang; David E. Irwin; Jason S. McCarley Visual search has memory Journal Article In: Psychological Science, vol. 12, no. 4, pp. 287–292, 2001. @article{Peterson2001, By monitoring subjects' eye movements during a visual search task, we examined the possibility that the mechanism responsi- ble for guiding attention during visual search has no memory for which locations have already been examined. Subjects did reexamine some items during their search, but the pattern of revisitations did not fit the predictions of the memoryless search model. In addition, a large pro- portion of the refixations were directed at the target, suggesting that the revisitations were due to subjects' remembering which items had not been adequately identified. We also examined the patterns of fixations and compared them with the predictions of a memoryless search model. Subjects' fixation patterns showed an increasing hazard function, whereas the memoryless model predicts a flat function. Lastly, we found no evidence suggesting that fixations were guided by amnesic co- vert scans that scouted the environment for new items during fixations. Results do not support the claims of the memoryless search model, and instead suggest that visual search does have memory. |
Marc Pomplun; Eyal M. Reingold; Jiye Shen Investigating the visual span in comparative search: The effects of task difficulty and divided attention Journal Article In: Cognition, vol. 81, no. 2, pp. B57–B67, 2001. @article{Pomplun2001, In three experiments, participants' visual span was measured in a comparative visual search task in which they had to detect a local match or mismatch between two displays presented side by side. Experiment 1 manipulated the difficulty of the comparative visual search task by contrasting a mismatch detection task with a substantially more difficult match detection task. In Experiment 2, participants were tested in a single-task condition involving only the visual task and a dual-task condition in which they concurrently performed an auditory task. Finally, in Experiment 3, participants performed two dual-task conditions, which differed in the difficulty of the concurrent auditory task. Both the comparative search task difficulty (Experiment 1) and the divided attention manipulation (Experiments 2 and 3) produced strong effects on visual span size. |
Marc Pomplun; Eyal M. Reingold; Jiye Shen The effects of peripheral and parafoveal cueing and masking on saccadic selectivity in a gaze-contingent window paradigm Journal Article In: Vision Research, vol. 41, no. 21, pp. 2757–2769, 2001. @article{Pomplun2001a, The present study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing conditions, the information shown outside the gaze-contingent window was restricted to the feature or feature pair shared between the target and a particular distractor type. In the masking conditions, no stimulus features were shown outside the window. Significant cueing and masking effects on saccadic selectivity were observed for saccades directed at items within the window, where all features were visible across experimental conditions. Cueing a particular feature or feature pair biased saccadic selectivity towards this feature or feature pair, while masking generally reduced saccadic selectivity. These findings support the concept of visual guidance being a preattentive process that operates in parallel across the display. |
Diane E. Williams; Eyal M. Reingold Preattentive guidance of eye movements during triple conjunction search tasks: The effects of feature discriminability and saccadic amplitude Journal Article In: Psychonomic Bulletin & Review, vol. 8, no. 3, pp. 476–488, 2001. @article{Williams2001, Eye movements were monitored during the performance of triple conjunction search tasks. Stimuli varied in color, shape, and orientation. Across trials, the target was either present or absent, and displays consisted of 6, 12, or 24 stimuli. Stimulus discriminability was manipulated for the shape dimension, with half of the participants seeing displays of Es and Fs (low-discriminability [LD] condition) and half seeing displays of Cs and Ts (high-discriminability [HD] condition). Participants in both conditions performed two search tasks. In the single-feature (SF) task, the target stimulus shared one feature with each of the distractors, whereas in the two-feature (TF) task, it shared two features with each distractor. An examination of saccadic endpoints revealed that participants were more likely to fixate on distractor stimuli sharing color (SF task) or color and shape (TF task) with the target. This was a robust finding, being observed across participants, saccades of different amplitudes and sequential position, and following short and long latencies to move. The extent to which participants made use of shape information increased with discriminability. |
Jie-Li Tsai A multichannel PC tachistoscope with high resolution and fast display change capability Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 33, no. 4, pp. 524–531, 2001. @article{Tsai2001, The number of channels that PC tachistoscopes can have has increased recently (Bokhorst, 1995; Myors, 1998); however, neither the quality of display nor speed of image switching has been improved. This article shows the capability of VESA's VBE 3.0 standard (1998) for increasing the number of channels of high-quality images. And the refresh rate can be set to the fastest cathode ray tube (CRT) scanning rate the monitor can tolerate in order to reduce the timing delay of changing display. A PCTSCOPE library was written in C to provide these capabilities, which is compatible with conventional DOS real mode. The PC tachistoscope can have numbers of channels with various resolutions and colors and different refresh rates. For example, 25 images with the resolution of 640 x 480 pixels and 256 colors can be loaded to video memory, and vertical refresh rate can be set to 180 Hz. It takes less than 6 msec to change the display among 25 channels in synchronizing with the start of the video scanning frame. In this library, the number of channels, the resolution of the images, and the speed of changing display all are improved. The multichannel PC tachistoscope with this technique is especially suitable for research requiring high-quality images and rapid successive presentation of stimuli. |
Risto Näsänen; Helena Ojanpää; Ilpo Kojo Effect of stimulus contrast on performance and eye movements in visual search Journal Article In: Vision Research, vol. 41, no. 14, pp. 1817–1824, 2001. @article{Naesaenen2001a, 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. |
Sebastiaan F. W. Neggers; Harold Bekkering Gaze anchoring to a pointing target is present during the entire pointing movement and Is driven by a non-visual signal Journal Article In: Journal of Neurophysiology, vol. 86, no. 2, pp. 961–970, 2001. @article{Neggers2001, A well-coordinated pattern of eye and hand movements can be observed during goal-directed arm movements. Typically, a saccadic eye movement precedes the arm movement, and its occurrence is temporally correlated with the start of the arm movement. Furthermore, the coupling of gaze and aiming movements is also observable after pointing initiation. It has recently been observed that saccades cannot be directed to new target stimuli, away from a pointing target stimulus. Saccades directed to targets presented during the final phase of a pointing movement were delayed until after pointing movement offset (“gaze anchoring”). The present study investigated whether ocular gaze is anchored to a pointing target during the entire pointing movement. In experiment 1, new targets were presented at various times during the duration of a pointing movement, triggered by the kinematics arm moment itself (movement onset, peak acceleration/velocity/deceleration, and offset). Subjects had to make a saccade to the new target as fast as possible while maintaining the pointing movement to the initial target. Saccadic latencies were increased by an amount of time that approximately equaled the remaining pointing time after saccadic target presentation, with the majority of saccades executed after pointing movement offset. The nature of the signal driving gaze stabilization during pointing was investigated in exper- iment 2. In previous experiments where ocular gaze was anchored to a pointing target, subjects could always see their moving arm, thus it was unknown whether a visual image of the moving arm, an afferent (proprioceptive) signal or an efferent (motor control related) signal produced gaze anchoring. In experiment 2 subjects had to point with or without vision of the moving arm to test whether a visual signal is used to anchor gaze to a pointing target. Results indicate that gaze anchoring was also observed without vision of the moving arm. The findings support the existence of a mechanism enforcing ocular gaze anchoring during the entire duration of a pointing movement. Moreover, such a mechanism uses an internally generated, or proprioceptive, nonvisual signal. Possible neural substrates underlying these processes are discussed, as well as the role of selective attention. |
John F. Soechting; Kevin C. Engel; Martha Flanders The Duncker Illusion and eye–hand coordination Journal Article In: Journal of Neurophysiology, vol. 85, no. 2, pp. 843–854, 2001. @article{Soechting2001, A moving background alters the perceived direction of target motion (the Duncker illusion). To test whether this illusion also affects pointing movements to remembered/extrapolated target locations, we constructed a display in which a target moved in a straight line and disappeared behind a band of moving random dots. Subjects were required to touch the spot where the target would emerge from the occlusion. The four directions of random-dot motion induced pointing errors that were predictable from the Duncker illusion. Because it has been previously established that saccadic direction is influenced by this illusion, gaze was subsequently recorded in a second series of experiments while subjects performed the pointing task and a similar task with eye-tracking only. In the pointing task, subjects typically saccaded to the lower border of the occlusion zone as soon as the target disappeared and then tried to maintain fixation at that spot. However, it was particularly obvious in the eye-tracking-only condition that horizontally moving random dots generally evoked an appreciable ocular following response, altering the gaze direction. Hand-pointing errors were related to the saccadic gaze error but were more highly correlated with final gaze errors (resulting from the initial saccade and the subsequent ocular following response). The results suggest a model of limb control in which gaze position can provide the target signal for limb movement. |
David A. Leopold; Alice J. O. Toole; Thomas Vetter; Volker Blanz Prototype-referenced shape encoding revealed by high-level aftereffects Journal Article In: Nature Neuroscience, vol. 4, no. 1, pp. 89–94, 2001. @article{Leopold2001, We used high-level configural aftereffects induced by adaptation to realistic faces to investigate visual representations underlying complex pattern perception. We found that exposure to an individual face for a few seconds generated a significant and precise bias in the subsequent perception of face identity. In the context of a computationally derived 'face space,' adaptation specifically shifted perception along a trajectory passing through the adapting and average faces, selectively facilitating recognition of a test face lying on this trajectory and impairing recognition of other faces. The results suggest that the encoding of faces and other complex patterns draws upon contrastive neural mechanisms that reference the central tendency of the stimulus category. |
Arthur F. Kramer; Nicholas D. Cassavaugh; David E. Irwin; Matthew S. Peterson; Sowon Hahn Influence of single and multiple onset distractors on visual search for singleton targets Journal Article In: Perception and Psychophysics, vol. 63, no. 6, pp. 952–968, 2001. @article{Kramer2001, In three experiments, we examined attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside of it. In Experiment 1, task-irrelevant sudden onsets appeared simultaneously on half the trials with the presentation of the color singleton target. Response times (RTs) were longer when onsets appeared in the display regardless of the number of onsets. Eye-scan strategies were also disrupted by the appearance of the onset distractors, although the proportion of trials on which the eyes were directed to the onsets was the same regardless of the number of onsets. In Experiment 2, we manipulated the time of presentation of two task-irrelevant onsets in order to further examine whether multiple onsets would be attended and fixated prior to attending a color singleton target. Again, subjects made a saccade to a task-irrelevant onset on a substantial proportion of trials prior to fixating the target. However, saccades to the second onset were rare. Experiment 3 served as a replication of Experiment 1 but without the requirement for subjects to move their eyes to detect and identify the singleton target. The RT results were consistent with those in Experiment 1; dual onsets had no larger an effect on response speed than single onset distractors. These data are discussed in terms of the interaction between top-down and bottom-up control of attention and the eyes. |
Ch. Klein; P. Berg In: Psychophysiology, vol. 38, no. 4, pp. 704–711, 2001. @article{Klein2001, The aim of the present study was the comparative assessment of the 4-week test-retest stabilities of the saccadic CNV (sCNV) and saccadic reaction times (SRT) during the execution of pro- and antisaccades, as well as the stability of RT during execution of two neuropsychological tests of alertness and S-R incompatibility. Prosaccades were elicited under the 200-ms gap and overlap conditions, antisaccades under the overlap condition (64 trials each). The EEG was recorded from 25 channels with a DC amplifier (MES, Munich). Data of 20 healthy participants were statistically analyzed. We found high test-retest correlations for all SRT (.76 < or = r(tt) < or = .88) and neuropsychological (.62 < or = r(tt) < or = .88) measures. For the sCNV, coefficients ranging between .58 (pro/gap) and .77 (anti/overlap) were obtained. Whereas SRT were significantly faster during the second than during the first session, group means for the saccadic CNV were stable across the sessions. Our results suggest high 4-week stability of individual differences in SRT, and moderate to good stabilities of saccadic CNV amplitudes. Our results recommend these "traitlike" measures to be used in individual differences research. |
Masud Husain; Sabira K. Mannan; Timothy L. Hodgson; Ewa Wojciulik; Jon Driver; Christopher Kennard Impaired spatial working memory across saccades contributes to abnormal search in parietal neglect Journal Article In: Brain, vol. 124, no. 5, pp. 941–952, 2001. @article{Husain2001, Visual neglect of left space following right parietal damage in humans involves a lateral bias in attention, apparent in many search tasks. We hypothesized that parietal neglect may also involve a failure to remember which locations have already been examined during visual search: an impairment in retaining searched locations across saccades. Using a new paradigm, we monitored gaze during search, while simultaneously probing whether observers judged they had found a new target, or judged instead that they were re-fixating a previously examined target. A patient with left neglect following focal right parietal infarction repeatedly re-fixated right locations. Critically, he often failed to remember that these locations had already been searched, treating old targets as new discoveries at an abnormal rate. In comparison, healthy age-matched control subjects rarely re-fixated targets, and mistook old targets as new targets even more rarely. The frequency of such mistakes in the parietal patient, for different conditions, correlated with the severity of his neglect. Control experiments indicated no perceptual localization deficit in non-search tasks. These results suggest a deficit in retaining searched locations across saccades in parietal neglect, in addition to the lateral spatial bias. Moreover, the former deficit exacerbates the latter, such that patients do not realize that the rightward locations favoured by their bias have already been examined during previous fixations and, for this reason, they saccade back to them repeatedly. The combination of the two deficits (a lateral bias plus a deficit in retaining locations already searched) may thus explain the pathological pattern of search that characterizes parietal neglect: why stimuli on the right are re-examined recursively, as if being searched for the first time, and hence why stimuli on the left continue to be ignored even with unlimited viewing time. These proposals accord with recent electrophysiological and functional imaging data, demonstrating posterior parietal involvement in the retention of target locations across saccades. |
Neil Charness; Eyal M. Reingold; Marc Pomplun; Dave M. Stampe The perceptual aspect of skilled performance in chess: Evidence from eye movements Journal Article In: Memory & Cognition, vol. 29, no. 8, pp. 1146–1152, 2001. @article{Charness2001, Expert and intermediate chess players attempted to choose the best move in five chess positions while their eye movements were monitored. Experts were faster and more accurate than intermediates in choosing the best move. Experts made fewer fixations per trial and greater amplitude saccades than did intermediates, but there was no difference in fixation duration across skill groups. Examining the spatial distribution of the first five fixations for each position by skill group revealed that experts produced more fixations on empty squares than did intermediates. When fixating pieces, experts produced a greater proportion of fixations on relevant pieces than did intermediates. It is argued that expert chess players perceptually encode chess configurations, rather than individual pieces, and, consequently, parafoveal or peripheral processing guides their eye movements, producing a pattern of saccadic selectivity by piece saliency. |
Uri Hasson; Talma Hendler; Dafna Ben Bashat; Rafael Malach Vase or face? A neural correlate of shape-selective grouping processes in the human brain Journal Article In: Journal of Cognitive Neuroscience, vol. 13, no. 6, pp. 744–753, 2001. @article{Hasson2001, Recent neuroimaging studies have described a differential activation pattern associated with specific object images (e.g., face-related and building-related activation) in human occipito-temporal cortex. However, it is as yet unclear to what extent this selectivity is due to differences in the statistics of local object features present in the different object categories, and to what extent it reflects holistic grouping processes operating across the entire object image. To resolve this question it is essential to use images in which identical sets of local features elicit the perception of different object categories. The classic Rubin vase-face illusion provides an excellent experimental set to test this question. In the illusion, the same local contours lead to the perception of different objects (vase or face). Here we employed a modified Rubin vase-face illusion to explore to what extent the activation in face-related regions is attributable to the presence of local face features, or is due to a more holistic grouping process that involves the entire face figure. Biasing cues (gratings and color) were used to control the perceptual state of the observer. We found enhanced activation in face-related regions during the "face profile" perceptual state compared to the "vase" perceptual state. Control images ruled out the involvement of the biasing cues in the effect. Thus, object-selective activation in human face-related regions entails global grouping processes that go beyond the local processing of stimulus features. |
Diane C. Gooding; Kathleen A. Tallent The association between antisaccade task and working memory task performance in schizophrenia and bipolar disorder Journal Article In: Journal of Nervous and Mental Disease, vol. 189, no. 1, pp. 8–16, 2001. @article{Gooding2001, To date, the research literature has yielded conflicting reports regarding the specificity of antisaccade deficits to schizophrenia. We sought to examine antisaccade and working memory task performance in schizophrenia patients and bipolar patients, as well as to examine the relationship between the two tasks in both patient populations. Thirty-four schizophrenia patients, 20 bipolar patients, and 30 nonpatient controls were administered saccadic inhibition (antisaccade), working memory, and sensorimotor tasks. Compared with the controls, the schizophrenia patients displayed both antisaccade deficits and working memory deficits. In contrast, the bipolar patients produced significantly more errors on the antisaccade task than the controls, though the bipolar group performed similarly to the control group on the working memory task. Mediational analyses demonstrated that working memory partially mediates the relationship between patients' diagnostic group status and antisaccade task performance; working memory performance contributed uniquely to the prediction of antisaccade task performance in the two patient groups. Antisaccade deficits do not appear specific to schizophrenia. The results suggest that in schizophrenia, working memory and antisaccade tasks are tapping similar cognitive processes, whereas in bipolar patients the processes underlying antisaccade and working memory performance are disparate. |
Harold H. Greene; Keith Rayner Eye-movement control in direction-coded visual search Journal Article In: Perception, vol. 30, no. 2, pp. 147–157, 2001. @article{Greene2001, Subjects searched for a target among distractors which were arranged randomly or such that each distractor provided information about the relative position of a target. Trials were presented either in a blocked design (so that the subjects knew a priori the contextual information in the display) or in a mixed design. When the distractors provided information about target position, there were (i) shorter manual RTs, (ii) fewer fixations made in search of the target, (iii) longer mean fixation durations, (iv) shorter initial fixation durations, (v) shorter mean gaze shifts, (vi) a smaller area of fixation dispersion, and (vii) a greater percentage of optimally directed saccades. Except for gaze shifts, the results were uninfluenced by whether or not there was a blocked or a mixed presentation. The results of the study suggest that despite noise in the search mechanism, fixation durations were adjusted to process directly the currently fixated element(s). |
Harold H. Greene; Keith Rayner Eye movements and familiarity effects in visual search Journal Article In: Vision Research, vol. 41, no. 27, pp. 3763–3773, 2001. @article{Greene2001a, Familiarity with the distractors around an unfamiliar target facilitates visual search. Three Experiments examined whether the effect occurs because fixations are (a) shorter and fewer, (b) shorter, but more abundant, (c) equally long, but fewer, or (d) longer, but fewer when distractors are familiar. Results indicated comparably long, but fewer fixations when distractors are familiar. Hence, the theory that unfamiliar distractors need longer processing is discounted. In a fourth Experiment, a gaze-contingent moving window paradigm was used to control peripheral processing. Results revealed a wider span of effective processing for familiar distractors. A hypothesis based on low-level physiological processes is introduced to account for the familiarity effect. |
2000 |
Kalanit Grill-Spector; Tammar Kushnir; Talma Hendler; Rafael Malach The dynamics of object-selective activation correlate with recognition performance in humans Journal Article In: Nature Neuroscience, vol. 3, no. 8, pp. 837–893, 2000. @article{GrillSpector2000, To investigate the relationship between perceptual awareness and brain activity, we measured both recogni-tion performance and fMRI signal from object-related areas in human cortex while images were presented briefly using a masking protocol. Our results suggest that recognition performance is correlated with selective activation in object areas. Selective activation was correlated to object naming when exposure duration was varied from 20 to 500 milliseconds. Subjects' recognition during identical visual stimulation could be enhanced by training, which also increased the fMRI signal. Overall, the correlation between recognition per- formance and fMRI signal was highest in occipitotemporal object areas (the lateral occipital complex). |
Iain D. Gilchrist; Monika Harvey Refixation frequency and memory mechanisms in visual search Journal Article In: Current Biology, vol. 10, no. 19, pp. 1209–1212, 2000. @article{Gilchrist2000, Visual search - looking for a target object in the presence of a number of distractor items - is an everyday activity for humans (for example, finding the car in a busy car park) and animals (for example, foraging for food). Our understanding of visual search has been enriched by an interdisciplinary effort using a wide range of research techniques including behavioural studies in humans [1], single-cell electrophysiology [2], transcranial magnetic stimulation [3], event-related potentials [4] and studies of patients with focal brain injury [5]. A central question is what kind of information controls the search process. Visual search is typically accompanied by a series of eye movements, and investigating the nature and location of fixations helps to identify the kind of information that might control the search process. It has already been demonstrated that objects are fixated if they are visually similar to the target [6]. Also, if an item has been fixated, it is less likely to be returned to on the subsequent saccade. This automatic process is referred to as inhibition of return (IOR [7,8]). Here, we investigated the role of memory for which items had been fixated previously. We found that, during search, subjects often refixated items that had been previously fixated. Although there were fewer return saccades than would be expected by chance, the number of refixations indicated limited functional memory, indeed the memory effects that were present may primarily be a result of IOR. |
Laurence R. Harris; Andrew T. Smith Interactions between first- and second-order motion revealed by optokinetic nystagmus Journal Article In: Experimental Brain Research, vol. 130, no. 1, pp. 67–72, 2000. @article{Harris2000, A previous study has suggested that second-order motion is ineffective at driving optokinetic nystagmus (OKN) when presented alone. First- and second-order motion cues interact in creating the perception of motion. Is there an interaction between first- and second-order cues in the control of eye movements? We presented combinations of first- and second-order cues moving in the same or opposite directions and measured the eye movements evoked, to look for a modification of the oculomotor response to first-order motion by simultaneously presented second-order cues. Dynamic random noise was used as a carrier for first- and second-order drifting gratings (13.4 degrees/s; 0.25 cycles/degree; 64 x 48 degrees screen viewed at 28.5 cm). Second-order gratings were defined by spatial modulation of the luminance flicker frequency of noise pixels of constant contrast (50%). A first-order, luminance-defined grating (13.4 degrees/s; 0.25 cycles/degree; variable contrast from 4-50%) was moved in either the same or the opposite direction. Eye movements were recorded by video-oculography from six subjects as they looked straight ahead. The gain (eye velocity/stimulus velocity) of first-order-evoked OKN increased with contrast. The presence of flicker-defined second-order motion in the opposite direction attenuated this OKN below a first-order contrast of 15%, although it had little effect at higher contrasts. When first- and second-order motion were in the same direction, there was an enhancement of the OKN response. We conclude that second-order motion can modify the optokinetic response to simultaneously presented first-order motion. |
Jiye Shen; Eyal M. Reingold; Marc Pomplun Distractor ratio influences patterns of eye movements during visual search Journal Article In: Perception, vol. 29, no. 2, pp. 241–250, 2000. @article{Shen2000, We examined the flexibility of guidance in a conjunctive search task by manipulating the ratios between different types of distractors. Participants were asked to decide whether a target was present or absent among distractors sharing either colour or shape. Results indicated a strong effect of distractor ratio on search performance. Shorter latency to move, faster manual response, and fewer fixations per trial were observed at extreme distractor ratios. The distribution of saccadic endpoints also varied flexibly as a function of distractor ratio. When there were very few same-colour distractors, the saccadic selectivity was biased towards the colour dimension. In contrast, when most of the distractors shared colour with the target, the saccadic selectivity was biased towards the shape dimension. Results are discussed within the framework of the guided search model. |
John Schlag; Rick H. Cai; Andrews Dorfman; Ali Mohempour; Madeleine Schlag-Rey Extrapolating movement without retinal motion Journal Article In: Nature, vol. 403, pp. 38–39, 2000. @article{Schlag2000, In contrast to the perception of a stationary object that is briefly flashed in the dark, a continuously visible moving object is seen as being ahead of its actual position at the time of the flash. An explanation for this simple effect, in which a stimulus moving on the retina is seen as being further along its path and not where it was in space when its signal impinged on the retina, is keenly debated. We show here that this illusion is not just limited to retinal motion, and that perceptual mislocalization occurs even when stimulus motion is inferred entirely from extra-retinal information, for example by movement of the observer's head or whole body, without retinal motion. The phenomenon may therefore rely on a much more general mechanism. |
William C. Schmidt Endogenous attention and illusory line motion reexamined Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 26, no. 3, pp. 980–996, 2000. @article{Schmidt2000, P. Downing and A. Treisman's (1997) failure to replicate an effect of endogenous attention on the direction of illusory line motion (ILM) was reexamined. Four experiments with slightly modified stimulus presentation methods based on gradient theories of ILM found that endogenous attention directed to 1 of 2 similar priming objects is capable of influencing experienced motion direction within a subsequently presented line. The endogenous effect on ILM was consistent with a concomitant response-time discrimination task, was robust across naive and informed participants, occurred whether eye fixation was monitored or not, and occurred under conditions where multiple motion response categories were available to participants. The endogenous effect disappeared when participants moved their eyes to the attended item, when there was no motivation to endogenously attend, and when the presentation methods of P. Downing and A. Treisman (1997) were used. |
Sebastiaan F. W. Neggers; Harold Bekkering Ocular gaze is anchored to the target of an ongoing pointing movement. Journal Article In: Journal of neurophysiology, vol. 83, no. 2, pp. 639–651, 2000. @article{Neggers2000, It is well known that, typically, saccadic eye movements precede goal-directed hand movements to a visual target stimulus. Also pointing in general is more accurate when the pointing target is gazed at. In this study, it is hypothesized that saccades are not only preceding pointing but that gaze also is stabilized during pointing in humans. Subjects, whose eye and pointing movements were recorded, had to make a hand movement and a saccade to a first target. At arm movement peak velocity, when the eyes are usually already fixating the first target, a new target appeared, and subjects had to make a saccade toward it (dynamical trial type). In the statical trial type, a new target was offered when pointing was just completed. In a control experiment, a sequence of two saccades had to be made, with two different interstimulus intervals (ISI), comparable with the ISIs found in the first experiment for dynamic and static trial types. In a third experiment, ocular fixation position and pointing target were dissociated, subjects pointed at not fixated targets. The results showed that latencies of saccades toward the second target were on average 155 ms longer in the dynamic trial types, compared with the static trial types. Saccades evoked during pointing appeared to be delayed with approximately the remaining deceleration time of the pointing movement, resulting in "normal" residual saccadic reaction times (RTs), measured from pointing movement offset to saccade movement onset. In the control experiment, the latency of the second saccade was on average only 29 ms larger when the two targets appeared with a short ISI compared with trials with long ISIs. Therefore the saccadic refractory period cannot be responsible for the substantially bigger delays that were found in the first experiment. The observed saccadic delay during pointing is modulated by the distance between ocular fixation position and pointing target. The largest delays were found when the targets coincided, the smallest delays when they were dissociated. In sum, our results provide evidence for an active saccadic inhibition process, presumably to keep steady ocular fixation at a pointing target and its surroundings. Possible neurophysiological substrates that might underlie the reported phenomena are discussed. |
Eli Brenner; Frans W. Cornelissen Separate simultaneous processing of egocentric and relative positions Journal Article In: Vision Research, vol. 40, no. 19, pp. 2557–2563, 2000. @article{Brenner2000, It is well established that all kinds of visual attributes are processed separately within the brain. This separation is related to differences in the information that is relevant for the different attributes. When attributes differ greatly (such as colour and motion) it is obvious that they must rely on different information. However, separating the processing of different attributes could also allow highly related attributes to evolve independently, so that they end up being judged on the basis of different types of information. Here, we examine the case of egocentric and relative localisation. For judging egocentric positions, the orientation of the eyes has to be taken into account. This is not so for judging relative positions. We demonstrate that these two attributes can be processed separately by showing that simultaneous judgements of relative and egocentric position differ in their dependency on eye orientation. Subjects pursued a moving dot. We flashed either single targets, or pairs of targets with a 67 ms interval between them, directly below the subjects' gaze. As the eyes were moving during the 67 ms interval, the retinal separation between pairs of targets was different from their actual separation. Subjects indicated the position at which they saw the targets with reasonable reproducibility, with a consistent bias in the direction of the eye movement. However, when two targets were flashed, the indicated separation between them usually coincided with their retinal separation, rather than with their actual separation. We conclude that egocentric and relative spatial positions can be estimated separately and simultaneously, on the basis of different types of information. |
D. W. J. Cabel; I. T. Armstrong; Eyal M. Reingold; D. P. Munoz Control of saccade initiation in a countermanding task using visual and auditory stop signals Journal Article In: Experimental Brain Research, vol. 133, no. 4, pp. 431–441, 2000. @article{Cabel2000, We examined inhibitory control in an oculomotor countermanding task, where the primary task required a saccadic eye movement be made to a target and a less-frequent secondary task required that the movement be halted. Previous studies have used a visual stimulus presented centrally on the fovea as the signal to stop or countermand a saccade. In these previous studies, there are at least two possible sources of saccadic inhibition: (1) sensory stimulation at the fovea can elicit a bottom-up mechanism, where a visual transient signal can delay or inhibit the developing saccade command; and (2) information based on the task instruction can be used to initiate a top-down mechanism to halt the movement. In the present study, we used both visual and auditory stop signals to test the hypothesis that the bottom-up mechanism is activated only after presentation of a foveal visual stop signal. Subjects were instructed first to look at a central spot and then to look to an eccentric visual target that appeared randomly to the left or right of center. On about one-third of the trials, a stop signal was presented. Three types of stop signals were used with equal probability: a broad-band noise burst (auditory), a central fixation spot (visual), and a combination of the auditory and visual stimuli (combined). Saccadic reaction time and stop-signal accuracy were used to calculate stop signal reaction time (SSRT), an estimate of the time required to inhibit the eye movement. Mean SSRT was longer for the auditory stop signals (201 ms) than for the signals with a foveal visual component (visual 113 ms; combined 91 ms). We conclude that a foveal visual stop signal in an oculomotor countermanding task changes the measure of inhibitory control to reflect not only inhibitory processes but also the sensory information afforded by stimulation at the fovea. |
David E. Irwin; Angela M. Colcombe; Arthur F. Kramer; Sowon Hahn Attentional and oculomotor capture by onset, luminance and color singletons Journal Article In: Vision Research, vol. 40, no. 10-12, pp. 1443–1458, 2000. @article{Irwin2000, In three experiments we investigated whether attentional and oculomotor capture occur only when object-defining abrupt onsets are used as distractors in a visual search task, or whether other salient stimuli also capture attention and the eyes even when they do not constitute new objects. The results showed that abrupt onsets (new objects) are especially effective in capturing attention and the eyes, but that luminance increments that do not accompany the appearance of new objects capture attention as well. Color singletons do not capture attention unless subjects have experienced the color singleton as a search target in a previous experimental session. Both abrupt onsets and luminance increments elicit reflexive, involuntary saccades whereas transient color changes do not. Implications for theories of attentional capture are discussed. |
Timothy L. Hodgson; Adnan Bajwa; Adrian M. Owen; Christopher Kennard The strategic control of gaze direction in the tower of London task Journal Article In: Journal of Cognitive Neuroscience, vol. 12, no. 5, pp. 894–907, 2000. @article{Hodgson2000, In this paper, we describe a novel approach to the study of problem solving involving the detailed analysis of natural scanning eye movements during the "one-touch" Tower-of-London (TOL) task. We showed subjects a series of pictures depicting two arrangements of colored balls in pockets within the upper and lower halves of a computer display. The task was to plan (but not to execute) the shortest movement sequence required to rearrange the balls in one half of the display (the Workspace) to match the arrangement in the opposite half (the Goalspace) and indicate the minimum number of moves required for problem solution. We report that subjects are more likely to look towards the Goalspace in the initial period after picture presentation, but bias gaze towards the Workspace during the middle of trials. Towards the end of a trial, subjects are once again more likely to fixate the Goalspace. This pattern is found regardless of whether the subjects solve problems by rearranging the balls in the lower or upper visual fields, demonstrating that this strategy correlates with discrete phases in problem solving. A second experiment showed that efficient planners direct their gaze selectively towards the problem critical balls in the Workspace. In contrast, individuals who make errors spend more time looking at irrelevant items and are strongly influenced by the movement strategy needed to solve the preceding problem. We conclude that efficient solution of the TOL requires the capacity to generate and flexibly shift between control sets, including those underlying ocular scanning. The role of working memory and the prefrontal cerebral cortex in the task are discussed. |
1999 |
Raymond M. Klein; W. Joseph Macinnes Inhibition of return is a foraging facilitator in visual search Journal Article In: Psychological Science, vol. 10, no. 4, pp. 346–352, 1999. @article{Klein1999, Using overt orienting, participants searched a complex visual scene for a camouflaged target (Waldo from the “Where's Waldo? ™ ” books). After several saccades, we presented an uncamou- flaged probe (black disk) while removing or maintaining the scene, and participants were required to locate this probe by foveating it. Inhibition of return was observed as a relative increase in the time required to locate these probes when they were in the general region of a previous fixation, but only when the search array remained present. Perhaps also reflecting inhibition of return, preprobe saccades showed a strong directional bias away from a previously fixated region. Together with recent studies that replicate the finding of inhibition at distractor locations following serial but not parallel visual search—so long as the search array remains visible—these data strongly support the proposal that inhibition of return functions to facilitate visual search by inhibiting orienting to previously examined locations. |
Arthur F. Kramer; Sowon Hahn; David E. Irwin; Jan Theeuwes Attentional capture and aging: Implications for visual search performance and oculomotor control Journal Article In: Psychology and Aging, vol. 14, no. 1, pp. 135–154, 1999. @article{Kramer1999, Two studies examined potential age-related differences in attentional capture. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. On half the trials, a new stimulus (i.e., a sudden onset) appeared simultaneously with the presentation of the color singleton target. The onset was always a task-irrelevant distractor. Response times were lengthened, for both young and old adults, whenever an onset distractor appeared, despite the fact that subjects reported being unaware of the appearance of the abrupt onset. Eye scan strategies were also disrupted by the appearance of the onset distractors. On about 40% of the trials on which an onset appeared, subjects made an eye movement to the task-irrelevant onset before moving their eyes to the target. Fixations close to the onset were brief, suggesting parallel programming of a reflexive eye movement to the onset and goal-directed eye movement to the target. Results are discussed in terms of age-related sparing of the attentional and oculomotor processes that underlie attentional capture. |
Sebastiaan F. W. Neggers; H. Bekkering Integration of visual and somatosensory target information in goal-directed eye and arm movements Journal Article In: Experimental Brain Research, vol. 125, no. 1, pp. 97–107, 1999. @article{Neggers1999, In this study, we compared separate and coordinated eye and hand movements towards visual or somatosensory target stimuli in a dark room, where no visual position information about the hand could be obtained. Experiment 1 showed that saccadic reaction times (RTs) were longer when directed to somatosensory targets than when directed to visual targets in both single- and dual-task conditions. However, for hand movements, this pattern was only found in the dual-task condition and not in the single-task condition. Experiment 1 also showed that correlations between saccadic and hand RTs were significantly higher when directed towards somatosensory targets than when directed towards visual targets. Importantly, experiment 2 indicated that this was not caused by differences in processing times at a perceptual level. Furthermore, hand-pointing accuracy was found to be higher when subjects had to move their eyes as well (dual task) compared to a single-task hand movement. However, this effect was more pronounced for movements to visual targets than to somatosensory targets. A schematic model of sensorimotor transformations for saccadic eye and goal-directed hand movements is proposed and possible shared mechanisms of the two motor systems are discussed. |
Diane C. Gooding Antisaccade task performance in questionnaire-identified schizotypes Journal Article In: Schizophrenia Research, vol. 35, no. 2, pp. 157–166, 1999. @article{Gooding1999, Individuals who scored high on Perceptual Aberration-Magical Ideation Scales (Per-Mag; n = 90), the Social Anhedonia Scale (SocAnh; n = 39), and control participants (n = 89) were administered saccadic refixation (prosaccade) and saccadic suppression (antisaccade) tasks. Eye movements were scored in terms of error rates and latency. None of the groups differed in terms of their performance on the prosaccade task. Both the Per-Mag (p < 0.01) and SocAnh (p < 0.05) groups exceeded the controls in terms of mean antisaccade errors. The high-risk groups did not differ from each other. Eighteen of the Per-Mag individuals and 10 of the SocAnh individuals displayed deviant antisaccade performance. These findings are particularly interesting in light of suggestive evidence that antisaccade task deficits may serve as a marker of susceptibility to schizophrenia. It is hypothesized that the individuals who scored aberrantly on the Chapman scales and displayed antisaccade performance deficits are most likely to be at risk for the development of psychosis. |
Jan Theeuwes; Arthur F. Kramer; Sowon Hahn; David E. Irwin; Gregory J. Zelinsky Influence of attentional capture on oculomotor control Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 25, no. 6, pp. 1595–1608, 1999. @article{Theeuwes1999, Previous research has shown that when searching for a color singleton, top-down control cannot prevent attentional capture by an abrupt visual onset. The present research addressed whether a task-irrelevant abrupt onset would affect eye movement behavior when searching for a color singleton. Results show that in many instances the eye moved in the direction of the task-irrelevant abrupt onset. There was evidence that top-down control could neither entirely prevent attentional capture by visual onsets nor prevent the eye from starting to move in the direction of the onset. Results suggest parallel programming of 2 saccades: 1 voluntary goal-directed eye movement toward the color singleton target and 1 stimulus-driven eye movement reflexively elicited by the abrupt onset. A neurophysiologically plausible model that can account for the current findings is discussed. |
Frans W. Cornelissen; John J. Dobbelsteen Heading detection with simulated visual field defects Journal Article In: Visual Impairment Research, vol. 1, no. 2, pp. 71–84, 1999. @article{Cornelissen1999, We examined how simulated visual field defects influence performance on a heading task to gain insight into the origins of the poorer performance seen in subjects with real visual field defects. We simulated tunnel vision and a central scotoma during ego-translation. Real-time gaze position was used to generate the appropriate optic flow pattern on the screen. The subjects' task was to direct their gaze at the continuously changing direction of heading. Limiting the peripheral view, as in tunnel vision, or introducing a central scotoma, as in macular degeneration, affected both the accuracy with which subjects could estimate heading direction as well as the time it took them to do this. Under natural circumstances, optic flow patterns can change both smoothly, such as during pursuit of an object, and more abruptly, such as when making saccades. Therefore, we examined performance during both of these types of change. While accuracy was the same under these conditions, processing time was differentially affected. When limiting peripheral view, the influence of the field defect on processing time was larger when the heading changed abruptly than when it changed smoothly. The reverse was the case for simulated central scotomas. The influence of the defect on processing time was largest when the head- ing changed smoothly. Our results further point out that the calculations underlying heading detection can be performed very quickly, with processing time strongly dependent upon the speed of the simulated translation and the size of the stimulated visual area. |
1998 |
Jan Theeuwes; Arthur F. Kramer; Sowon Hahn; David E. Irwin Our eyes do not always go where we want them to go: Capture of the eyes by new objects Journal Article In: Psychological Science, vol. 9, no. 5, pp. 379–385, 1998. @article{Theeuwes1998, Observers make rapid eye movements to examine the world around them. Before an eye movement is made, attention is covertly shifted to the location of the object of interest. The eyes typically will land at the position at which attention is directed. Here we report that a goal-directed eye movement toward a uniquely colored object is disrupted by the appearance of a new but task-irrelevant object, unless subjects have a sufficient amount of time to focus their attention on the location of the target prior to the appearance of the new object. In many instances, the eyes started moving toward the new object before gaze started to shift to the color-singleton target. The eyes often landed for a very short period of time (25–150 ms) near the new object. The results suggest parallel programming of two saccades: one voluntary, goal-directed eye movement toward the color-singleton target and one stimulus-driven eye movement reflexively elicited by the appearance of the new object. Neuroanatomical structures responsible for parallel programming of saccades are discussed. |
1997 |
Diane E. Williams; Eyal M. Reingold; Morris Moscovitch; Marlene Behrmann Patterns of eye movements during parallel and serial visual search tasks Journal Article In: Canadian Journal of Experimental Psychology, vol. 51, no. 2, pp. 151–164, 1997. @article{Williams1997, Eye movements were monitored while subjects performed parallel and serial search tasks. In Experiment 1a, subjects searched for an "O" among "X"s (parallel condition) and for a "T" among "L"s (serial condition). In the parallel condition in Experiment 1b, "[symbol: see text]" was the target, and "O"s were distractors; in the serial condition these stimuli switched roles. Displays contained 1, 12, or 24 stimuli, with both target-present and target-absent trials. RT and eye-movement measures (number of fixations, saccadic error, and latency to move) indicated that search efficiency was greatest in the parallel conditions, followed by the serial condition of experiment 1a and, finally, by the serial condition of Experiment 1b. This suggests that eye movements are correlated with the attentional processes underlying visual search. |