All EyeLink Eye Tracker Publications
All 14,000+ peer-reviewed EyeLink research publications up until 2025 (with some early 2026s) are listed below by year. You can search the publications library using keywords such as Visual Search, Smooth Pursuit, Parkinson’s, etc. You can also search for individual author names. Eye-tracking studies grouped by research area can be found on the solutions pages. If we missed any EyeLink eye-tracking papers, please email us!
2003 |
Casimir J. H. Ludwig; Iain D. Gilchrist Target similarity affects saccade curvature away from irrelevant onsets Journal Article In: Experimental Brain Research, vol. 152, no. 1, pp. 60–69, 2003. @article{Ludwig2003,Saccade curvature away from visual distractors is a measure of the salience of these distractors for the oculomotor system. Three experiments are reported in which the integration of luminance onset signals and target similarity signals is examined, using a saccade curvature paradigm. Observers made saccades to a no-onset colour target in one of two positions on the vertical meridian. On most trials, an abrupt onset distractor that was either similar or dissimilar to the target appeared left or right on the horizontal midline. Saccades curved away from the irrelevant onsets; however, the amount of curvature was modulated by target similarity only when the onset appeared before the target (experiment 2) or when saccade initiation was delayed (experiment 3). These results suggest that the initial response to the onset is stimulus-driven and mediated by its transient component. Over time, the response is integrated with and augmented by top-down inputs. Visual and non-visual signals converge onto a common motor map to determine an item's salience. |
Elliot M. Frohman; Padraig O'Suilleabhain; Richard B. Dewey; Teresa C. Frohman; Phillip D. Kramer A new measure of dysconjugacy in INO: The first-pass amplitude Journal Article In: Journal of the Neurological Sciences, vol. 210, no. 1-2, pp. 65–71, 2003. @article{Frohman2003,Background: The ratios of abducting to adducting eye movements (versional dysconjugacy index, VDI) for saccadic velocity and acceleration have been useful measures by which to objectively characterize internuclear ophthalmoparesis (INO). Amplitude measures of dysconjugacy have been less useful, given that many patients maintain the ability to ultimately reach a centrifugal fixation target and that traditional amplitude measures of VDI have focused on this 'final amplitude' (FA) position. Methods: We utilized infrared oculography to define a new amplitude measure of dysconjugacy in 42 multiple sclerosis (MS) patients with INO. The first-pass amplitude (FPA)-VDI is the ratio of abduction/adduction eye movement amplitudes computed at the time when the abducting eye initially achieves the centrifugal horizontal fixation target. Results: FPA-VDI values were significantly more sensitive and specific than FA-VDI values in demonstrating dysconjugacy in INO, and there was a 14-fold increase in dysconjugacy as measured by FPA-VDI Z-scores when compared to FA-VDI Z-scores. Conclusion: Consideration of velocity (pulse) and amplitude (step) components of dysconjugacy in patients with INO can provide a greater understanding of the dynamic aspects of this syndrome. We propose to characterize the relationship between the pathophysiology of INO and neuroradiologic measures of tissue injury in MS. |
Casimir J. H. Ludwig; Iain D. Gilchrist Goal-driven modulation of oculomotor capture Journal Article In: Perception and Psychophysics, vol. 65, no. 8, pp. 1243–1251, 2003. @article{Ludwig2003a,In a recent study, Ludwig and Gilchrist (2002) showed that stimulus-driven oculomotor capture by abrupt onset distractors was modulated by distractor-target similarity: Participants were more likely to fixate an irrelevant onset when it shared the target color. Here we test whether this pattern of performance is the result of (1) inhibition of all items in the distractor color, (2) a response bias to local color discontinuities, or (3) the integration of stimulus-driven abrupt onset signals with goal-driven information about the target features. The results of two experiments clearly support the third explanation. We conclude that oculomotor capture is modulated by, but not contingent upon, top-down control, and our findings argue for an integrative view of the saccadic system. |
Teresa C. Frohman; Elliot M. Frohman; Padraig O'Suilleabhain; A. R. Salter; Richard B. Dewey; N. Hogan; S. Galetta; A. G. Lee; D. Straumann; J. Noseworthy; D. Zee; J. Corbett; J. Corboy; V. M. Rivera; Phillip D. Kramer Accuracy of clinical detection of INO in MS: Corroboration with quantitative infrared oculography Journal Article In: Neurology, vol. 61, no. 6, pp. 848–850, 2003. @article{Frohman2003a,The authors compared the accuracy of clinical detection (by 279 physician observers) of internuclear ophthalmoparesis (INO) with that of quantitative infrared oculography. For the patients with mild adduction slowing, INO was not identified by 71%. Intermediate dysconjugacy was not detected by 25% of the evaluators. In the most severe cases, INO was not identified by only 6%. Oculographic techniques significantly enhance the precision of INO detection compared to the clinical exam. |
Masud Husain; Andrew Parton; Timothy L. Hodgson; Dominic J. Mort; Geraint Rees Self-control during response conflict by human supplementary eye field Journal Article In: Nature Neuroscience, vol. 6, no. 2, pp. 117–118, 2003. @article{Husain2003,Although medial frontal cortex is considered to have an important role in planning behavior and monitoring errors, the specific contributions of regions within it are poorly understood1, 2, 3. Here we report that a patient with a highly selective lesion of a medial frontal motor area—the supplementary eye field (SEF)—lacked control in changing the direction of his eye movement from either a previous intention or behavioral 'set'; however, he monitored his errors well and corrected them quickly. The results indicate a key new role for the SEF and show that medial frontal mechanisms for self-control of action may be highly specific, with the SEF critically involved in implementing oculomotor control during response conflict, but not in error monitoring. |
Ralf Engbert; Reinhold Kliegl Microsaccades uncover the orientation of covert attention Journal Article In: Vision Research, vol. 43, no. 9, pp. 1035–1045, 2003. @article{Engbert2003,Fixational eye movements are subdivided into tremor, drift, and microsaccades. All three types of miniature eye movements generate small random displacements of the retinal image when viewing a stationary scene. Here we investigate the modulation of microsaccades by shifts of covert attention in a classical spatial cueing paradigm. First, we replicate the suppression of microsaccades with a minimum rate about 150 ms after cue onset. Second, as a new finding we observe microsaccadic enhancement with a maximum rate about 350 ms after presentation of the cue. Third, we find a modulation of the orientation towards the cue direction. These multiple influences of visual attention on microsaccades accentuate their role for visual information processing. Furthermore, our results suggest that microsaccades can be used to map the orientation of visual attention in psychophysical experiments. |
Ryota Kanai; Josef N. Geest; Maarten A. Frens Inhibition of saccade initiation by preceding smooth pursuit Journal Article In: Experimental Brain Research, vol. 148, no. 3, pp. 300–307, 2003. @article{Kanai2003,In this study, we investigated the influence of smooth-pursuit eye movements on saccade initiation in response to a sudden jump of a continuously moving target. We replicated the finding by Tanaka et al. (1998) that saccadic eye movements in the direction opposite to preceding pursuit have longer latencies than those in the same direction. We confirmed that this asymmetry is indeed due to an inhibitory effect of smooth pursuit on saccade initiation in the opposite direction rather than facilitation of saccade initiation in the same direction. The inhibitory effect decreased strongly when subjects knew the jump direction in advance. This supports the notion that the prolonged latencies of backward saccades are not due to orbital mechanics or low-level motor processing. Furthermore, we found that the range of saccade direc- tions inhibited by a pursuit movement is broad, covering all directions that did not have the same horizontal component as the pursuit direction. This is in contrast with the predictions of “Inhibition of Saccade Return” (ISR, Hooge and Frens 2000), which is restricted to a smaller confined area. |
Raymond Bertram; Jukka Hyönä In: Journal of Memory and Language, vol. 48, pp. 615–634, 2003. @article{Bertram2003,This study explored whether the length of a complex word modifies the role of morphological structure in lexical processing: Does morphological structure play a similar role in short complex words that typically elicit one eye fixation (e.g., eyelid) as it does in long complex words that typically elicit two or more eye fixations (e.g., watercourse)? Two eye movement experiments with short vs. long Finnish compound words in context were conducted to find an answer to this question. In Experiment 1, a first-constituent frequency manipulation revealed solid effects for long compounds in early and late processing measures, but no effects for short compounds. In contrast, in Experiment 2, a whole-word frequency manipulation elicited solid effects for short compounds in early and late processing measures, but mainly late effects for long compounds. A race model, incorporating a headstart for the decomposition route, in case whole-word information of complex words cannot be extracted in a single fixation can explain the pattern of results. |
Nicholas D. Cassavaugh; Arthur F. Kramer; David E. Irwin Influence of task-irrelevant onset distractors on the visual search performance of young and old adults Journal Article In: Aging, Neuropsychology, and Cognition, vol. 10, no. 1, pp. 44–60, 2003. @article{Cassavaugh2003,We examined potential age-related differences in attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. 24 participants were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. Either single or dual onset task-irrelevant distractors were presented simultaneously with the color change that defined the target, or one onset distractor was presented prior to and another onset distractor was presented during the participant's initial eye movement away from fixation. Young and old adults misdirected their eyes to the single and dual onset task-irrelevant distractors, on an equivalent proportion of trials, relative to control trials. However, older adults' saccade latencies and RTs were influenced to a greater extent by onsets compared to younger adults'. These data are discussed in terms of age-related differences in attentional control and oculomotor capture. |
Jiye Shen; Eyal M. Reingold; Marc Pomplun Guidance of eye movements during conjunctive visual search: The distractor-ratio effect Journal Article In: Canadian Journal of Experimental Psychology, vol. 57, no. 2, pp. 76–96, 2003. @article{srp03,The distractor-ratio effect refers to the finding that search performance in a conjunctive visual search task depends on the relative frequency of two types or subsets of distractors when the total number of items in a display is fixed. Previously, Shen, Reingold, and Pomplun (2000) examined participants' patterns of eye movements in a distractor-ratio paradigm and demonstrated that on any given trial saccadic endpoints were biased towards the smaller subset of distractors and participants flexibly switched between different subsets across trials. The current study explored the boundary conditions of this tendency to flexibly search through a smaller subset of distractors by examining the influence of several manipulations known to modulate search efficiency, including stimulus discriminability (Experiment 1), within-dimension versus cross-dimension conjunction search and distractor heterogeneity (Experiment 2). The results indicated that the flexibility of visual guidance and saccadic bias exemplified by the distractor-ratio effect is a robust phenomenon that mediates search efficiency by adapting to changes in the relative informativeness of stimulus dimensions and features. |
I. T. Armstrong; Douglas P. Munoz Inhibitory control of eye movements during oculomotor countermanding in adults with attention-deficit hyperactivity disorder Journal Article In: Experimental Brain Research, vol. 152, no. 4, pp. 444–452, 2003. @article{Armstrong2003a,Children with attention-deficit hyperactivity disorder (ADHD) are impulsive, and that impulsiveness can be measured using a countermanding task. Although the overt behaviors of ADHD attenuate with age, it is not clear how well impulsiveness is controlled in adults with ADHD. We tested ADHD adults with an oculomotor countermanding task. The task included two conditions: on 75% of the trials, participants viewed a central fixation marker and then looked to an eccentric target that appeared simultaneous with the disappearance of the fixation marker; on 25% of the trials, a signal was presented at variable delays after target appearance. The signal instructed subjects to stop, or countermand, an eye movement to the target. A correct movement in this case would be to hold gaze at the central fixation location. We expected ADHD participants to be impulsive in their countermanding performance. Additionally, we expected that a visual stop signal at the central fixation location would assist oculomotor countermanding because the signal is presented in the "stop" location, at fixation. To test whether a central stop signal positively biased countermanding, we used a three types of stop signal to instruct the stop: a central visual marker, a peripheral visual signal, and a non-localized sound. All subjects performed best with the central visual stop signal. Subjects with ADHD were less able to countermand eye movements and were influenced more negatively by the non-central signals. Oculomotor countermanding may be useful for quantifying impulsive dysfunction in adults with ADHD especially if a non-central stop signal is applied. |
I. T. Armstrong; Douglas P. Munoz Attentional blink in adults with attention-deficit hyperactivity disorder: Influence of eye movements Journal Article In: Experimental Brain Research, vol. 152, no. 2, pp. 243–250, 2003. @article{Armstrong2003,The attentional blink paradigm tests attention by overloading it: a list of stimuli is presented very rapidly one after another at the same location on a computer screen, each item overwriting the last, and participants monitor the list using two criteria [e.g. detect the target (red letter) and identify the probe (letter p)]. If the interval between the target and the probe is greater than about 500 ms, both are usually reported correctly, but, when the interval between the target and the probe is within 200-500 ms, report of the probe declines. This decline is the attentional blink, an interval of time when attention is supposedly switching from the first criterion to the second. The attentional blink paradigm should be difficult to perform correctly without vigilantly attending to the rapidly presented list. Vigilance tasks are often used to assess attention-deficit hyperactivity disorder (ADHD). Symptoms of the disorder include hyperactivity and attentional dysfunction; however, some people with ADHD also have difficulty maintaining gaze at a fixed location. We tested 15 adults with ADHD and their age- and sex-matched controls, measuring accuracy and gaze stability during the attentional blink task. ADHD participants reported fewer targets and probes, took longer to recover from the attentional blink, made more eye movements, and made identification errors consistent with non-perception of the letter list. In contrast, errors made by control participants were consistent with guessing (i.e., report of a letter immediately preceding or succeeding the correct letter). Excessive eye movements result in poorer performance for all participants; however, error patterns confirm that the weak performance of ADHD participants may be related to gaze instability as well as to attentional dysfunction. |
Junghyun Park; Madeleine Schlag-Rey; John Schlag Voluntary action expands perceived duration of its sensory consequence Journal Article In: Experimental Brain Research, vol. 149, no. 4, pp. 527–529, 2003. @article{Park2003,When we look at a clock with a hand showing seconds, the hand sometimes appears to stay longer at its first-seen position than at the following positions, evoking an illusion of chronostasis. This illusory extension of perceived duration has been shown to be coupled to saccadic eye movement and it has been suggested to serve as a mechanism of maintaining spatial stability across the saccade. Here, we examined the effects of three kinds of voluntary movements on the illusion of chronostasis: key press, voice command, and saccadic eye movement. We found that the illusion can occur with all three kinds of voluntary movements if such movements start the clock immediately. When a delay is introduced between the voluntary movement and the start of the clock, the delay itself is overestimated. These results indicate that the illusion of chronostasis is not specific to saccadic eye movement, and may therefore involve a more general mechanism of how voluntary action influences time perception. |
Junghyun Park; Madeleine Schlag-Rey; John Schlag Spatial localization precedes temporal determination in visual perception Journal Article In: Vision Research, vol. 43, no. 15, pp. 1667–1674, 2003. @article{Park2003a,The temporal order of two spots of light successively appearing in the dark, just before a saccade, influences their perceived spatial relation. Both spots are mislocalized in the saccade direction - the second more so than the first - because mislocalization grows as time elapses from stimulus to saccade onset. On the other hand, the perceived order of the two spots may be altered if the second spot is at the focus of spatial attention. How would these illusory perceptions of space and time interact when they are brought to play together? Could they be independent or could one perception depend on the other? Here we show that perceived location of stimuli is not affected by illusory temporal order, whereas perceived temporal order is affected by misperceived location. The results suggest that the brain processes spatial location of visual stimuli before processing their temporal order. |
Anne Pier Salverda; Delphine Dahan; James M. McQueen The role of prosodic boundaries in the resolution of lexical embedding in speech comprehension Journal Article In: Cognition, vol. 90, no. 1, pp. 51–89, 2003. @article{Salverda2003,Participants' eye movements were monitored as they heard sentences and saw four pictured objects on a computer screen. Participants were instructed to click on the object mentioned in the sentence. There were more transitory fixations to pictures representing monosyllabic words (e.g. ham) when the first syllable of the target word (e.g. hamster) had been replaced by a recording of the monosyllabic word than when it came from a different recording of the target word. This demonstrates that a phonemically identical sequence can contain cues that modulate its lexical interpretation. This effect was governed by the duration of the sequence, rather than by its origin (i.e. which type of word it came from). The longer the sequence, the more monosyllabic-word interpretations it generated. We argue that cues to lexical-embedding disambiguation, such as segmental lengthening, result from the realization of a prosodic boundary that often but not always follows monosyllabic words, and that lexical candidates whose word boundaries are aligned with prosodic boundaries are favored in the word-recognition process. |
Nadia Alahyane; Denis Pélisson Adaptation of saccadic eye movements: Transfer and specificity Journal Article In: Annals of the New York Academy of Sciences, vol. 1004, no. 1, pp. 69–77, 2003. @article{Alahyane2003,The present study was designed to test whether the adaptation of saccadic eye movements depends only on the eye displacement vector of the trained saccade or also on eye position information. Using the double-step target paradigm in eight human subjects, we first induced in a single session two "opposite directions adaptations" (ODA) of horizontal saccades of the same vector. Each ODA (backward or forward) was linked to one vertical eye position (12.5 degrees up or 25 degrees down) and alternated from trial to trial. The results showed that opposite changes of saccade amplitude can develop simultaneously, indicating that saccadic adaptation depends on orbital eye position. This finding has important functional implications because in everyday life our eyes saccade from constantly changing orbital positions. A comparison of these data to two control conditions in which training trials of a single type (backward or forward) were presented at both 12.5 degrees and -25 degrees eye elevations further indicated that eye position specificity is complete for backward, but not for forward, adaptation. Finally, the control conditions also indicated that the adaptation of a single saccade fully transferred to untrained saccades of the same vector, but initiated from different vertical eye positions. In conclusion, our study indicates that saccadic adaptation mechanisms use vectorial eye displacement signals, but can also take eye position signals into account as a contextual cue when the training involves conflicting saccade amplitude changes |
Jörg Sommerhalder; Evelyne Oueghlani; Marc Bagnoud; Ute Leonards; Avinoam B. Safran; Marco Pelizzone Simulation of artificial vision: I. Eccentric reading of isolated words, and perceptual learning Journal Article In: Vision Research, vol. 43, no. 3, pp. 269–283, 2003. @article{soblsp03,Simulations of artificial vision were performed to assess "minimum requirements for useful artificial vision". Retinal prostheses will be implanted at a fixed (and probably eccentric) location of the retina. To mimic this condition on normal observers, we projected stimuli of various sizes and content on a defined stabilised area of the visual field. In experiment 1, we asked subjects to read isolated 4-letter words presented at various degrees of pixelisation and at various eccentricities. Reading performance dropped abruptly when the number of pixels was reduced below a certain threshold. For central reading, a viewing area containing about 300 pixels was necessary for close to perfect reading (>90% correctly read words). At eccentricities beyond 10°, close to perfect reading was never achieved even if more than 300 pixels were used. A control experiment using isolated letter recognition in the same conditions suggested that lower reading performance at high eccentricity was in part due to the "crowding effect". In experiment 2, we investigated whether the task of eccentric reading under such specific conditions could be improved by training. Two subjects, naive to this task, were trained to read pixelised 4-letter words presented at 15° eccentricity. Reading performance of both subjects increased impressively throughout the experiment. Low initial reading scores (range 6%-23% correct) improved impressively (range 64%-85% correct) after about one month of training (about 1 h/day). Control tests demonstrated that the learning process consisted essentially in an adaptation to use an eccentric area of the retina for reading. These results indicate that functional retinal implants consisting of more than 300 stimulation contacts will be needed. They might successfully restore some reading abilities in blind patients, even if they have to be placed outside the foveal area. Reaching optimal performance may, however, require a significant adaptation process. |
Richard Godijn; Jan Theeuwes Parallel allocation of attention prior to the execution of saccade sequences Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 29, no. 5, pp. 882–896, 2003. @article{Godijn2003,In a series of 5 experiments, the allocation of attention prior to the execution of saccade sequences was examined by using a dual-task paradigm. In the primary task, participants were required to execute a sequence of 2 endogenous saccades. The secondary task was a forced-choice letter identification task. During the programming of the saccade sequences, letters were briefly presented at the saccade goals and at no-saccade locations. The results showed that performance was better for letters presented at any of the saccade goals than for letters presented at any of the no-saccade locations. The results support a spatial model that assumes that prior to the execution of a saccade sequence, attention is allocated in parallel to all saccade goals. |
Lars Lünenburger; Klaus-Peter Hoffmann Arm movement and gap as factors influencing the reaction time of the second saccade in a double-step task Journal Article In: European Journal of Neuroscience, vol. 17, no. 11, pp. 2481–91, 2003. @article{Luenenburger2003,To guide our hand for reaching, we explore our visual environment by sequences of saccades. In the present paper, we studied the eye and hand movements of human subjects looking or looking and pointing at a target that is instantaneously displaced two times (double-step task). It was previously shown that the second saccade has a much longer reaction time than the first one [Feinstein & Williams (1972) Vision Res., 12, 33-44]. The second reaction time is even longer if the subject also has to point to the target with the hand [Lünenburger et al. (2000) Eur. J. Neurosci., 12, 4107-4116]. The conditions and objective for these effects are further examined in the present paper. It is shown that vision of the hand reduces the first and second saccadic reaction times in parallel. The second reaction time is prolonged for shorter delays between both target steps as well as for larger amplitudes of the second saccade. However, the long second reaction time does not reflect an absolute saccadic refractory period, because a gap before the second target step reduces the second reaction time to a value similar to the first. Hand response time and average hand velocity were increased when the second target step was larger. The response time for the eyes was about 30% of the response time of the hand. We argue that the observed effects reflect the coordination of eye and hand movement to allow a precise and efficient reaching behaviour. |
Timothy Desmet; Edward Gibson Disambiguation preferences and corpus frequencies in noun phrase conjunction Journal Article In: Journal of Memory and Language, vol. 49, no. 3, pp. 353–374, 2003. @article{Desmet2003,Gibson and Schütze (1999) showed that on-line disambiguation preferences do not always mirror corpus frequencies. When presented with a syntactic ambiguity involving the conjunction of a noun phrase to three possible attachment sites, participants were faster to read attachments to the first site than attachments to the second one, although the latter were shown to be more frequent in text corpora. In the present study, we investigated whether a particular feature in their items - disambiguation using the pronoun 'one'-could account for this discrepancy. The results of a corpus analysis and two on-line reading experiments showed that the presence of this pronoun is indeed responsible for the high attachment preference in the conjunction ambiguity. We conclude that for this syntactic ambiguity there is no discrepancy between on-line preferences and corpus frequencies. Consequently, there is no need to assume different processes underlying sentence comprehension and sentence production on the basis of the noun phrase conjunction ambiguity. |
Thomas Wynn; Frederick Coolidge The role of working memory in the evolution of managed foraging Journal Article In: Before Farming, no. 2, pp. 1–16, 2003. @article{Wynn2003,This article proposes that a relatively simple evolutionary development in human cognition enabled the development of managed foraging systems and, ultimately, agriculture. This development, an increase in the capacity of working memory, resulted in an enhancement of such specific cognitive abilities as response inhibition, response preparation, resistance to interference, and the ability to integrate action across space and time. All are required for modern managed foraging systems, including hunting and gathering and agriculture. Archaeological evidence provides strong evidence for managed foraging by the middle of the European Upper Palaeolithic and South African Later Stone Age, and independent evidence for enhanced working memory capacity slightly earlier. This fits the hypothesis that enhanced working memory capacity was a relatively recent development in human evolution, and one that enabled not just managed foraging, but perhaps modern culture itself. |
Heiner Deubel; Werner X. Schneider Delayed saccades, but not delayed manual aiming movements, require visual attention shifts Journal Article In: Annals of the New York Academy of Sciences, vol. 1004, pp. 289–296, 2003. @article{Deubel2003,Several studies have shown that during the preparation of a goal-directed movement, perceptual selection (i.e., visual attention) and action selection (the selection of the movement target) are closely coupled. Here, we study attentional selection in situations in which delayed saccadic eye movements and delayed manual movements are prepared. A dual-task paradigm was used which combined the movement preparation with a perceptual discrimination task. The results demonstrate a fundamental difference between the preparation of saccades and of manual reaching. For delayed saccades, attention is pinned to the saccade target until the onset of the response. This does not hold for manual reaching, however. Although fast reaching movements require attention, reaches delayed more than 300 ms after movement cue onset can be already performed "off-line"; that is, attention can be withdrawn from the movement target. |
Chiang-Shan Ray Li; Hsueh-Ling Chang; Shih Chieh Lin Inhibition of return in children with attention deficit hyperactivity disorder Journal Article In: Experimental Brain Research, vol. 149, no. 1, pp. 125–130, 2003. @article{Li2003,Earlier studies have suggested an impairment in the attention and eye movement control of children with ADHD. An important phenomenon in the control of attentional shifts and eye movements is the inhibition of return (IOR), which states that our brain works in a way that prevents our attention from returning to a spatial location that has been attended to, either overtly or covertly. This current study addresses whether the IOR in oculomotor planning is compromised in children with ADHD. Eleven ADHD and 12 age- and gender-matched control subjects participated in a behavioral task, in which they made saccades to a peripheral target after a valid, invalid or neutral cue. The latency difference between cued and uncued saccades over a range of cue-target onset asynchrony as well as the positive component of this latency profile (i.e., IOR) was compared between groups. The results show that ADHD children demonstrate a biphasic latency profile that is grossly similar to that observed in control subjects, although the magnitude of IOR appears to be slightly smaller in ADHD subjects. These preliminary results suggest that the inhibitory attention mechanism subserving IOR is at least not fully compromised in ADHD children. |
Avital Deutsch; Ram Frost; Sharon Pelleg; Alexander Pollatsek; Keith Rayner Early morphological effects in reading: Evidence from parafoveal preview benefit in Hebrew Journal Article In: Psychonomic Bulletin & Review, vol. 10, no. 2, pp. 415–422, 2003. @article{Deutsch2003,Hebrew words are composed of two interwoven morphemes: a triconsonantal root and a word pattern.We examined the role of the root morpheme in word identificationby assessingthe benefit of presentation of a parafoveal previewword derived from the same root as a target word. Although the letter information of the preview was not consciously perceived, a preview of a word derived from the same root morpheme as the foveal target word facilitated eye-movement measures of first-pass reading (i.e., first fixation and gaze duration). These results are the first to demonstrate early morphological effects in the context of sentence reading in which no external task is imposed on the reader, and converge with previous findings of morphemic priming in Hebrew using the masked priming paradigm, and morphemic parafoveal preview benefit effects in a single-word identification task. |
Frank A. Proudlock; Himanshu Shekhar; Irene Gottlob Coordination of eye and head movements during reading Journal Article In: Investigative Ophthalmology & Visual Science, vol. 44, no. 7, pp. 2991–2998, 2003. @article{Proudlock2003,PURPOSE. There is little information regarding the characteristics of head movements during reading. This study was undertaken to investigate horizontal and vertical head movements during two different reading tasks. METHODS. Head and eye movements were monitored with an infrared pupil and head tracker in 15 subjects during repeated reading of text from an A4-sized card and a card 90 degrees wide. In addition, head and eye movements were recorded in 45 subjects to compare head movement propensity during an A4 text-reading task and a saccadic task of an equivalent gaze shift. RESULTS. During the A4 standard reading task, horizontal and vertical head movements accounted for 4.7% and 28.7% of the gaze shift, respectively. During the 90 degrees text reading, horizontal head movements accounted for 40.3% of the gaze amplitude, and vertical head movements accounted for 28.4%. Horizontal gaze velocities increased significantly on repeated A4 and 90degrees text readings, as did horizontal head velocities and amplitudes. Reading head movement propensities were significantly smaller than saccadic head movement propensities (P < 0.001). CONCLUSIONS. Head movement strategies are rapidly switched between the A4 and 90 degrees text-reading paradigms. They are minimized during A4 text reading but actively assist the gaze strategy during 90degrees text reading. Horizontal head movement is reduced during A4 reading compared to the equivalent saccadic task and may be suppressed to improve fixation stability. The results support the view that the head and eye movement system is a highly coupled but extremely flexible system. |
Monika Harvey; Iain D. Gilchrist; Bettina Olk; Keith Muir Eye-movement patterns do not mediate size distortion effects in hemispatial neglect: Looking without seeing Journal Article In: Neuropsychologia, vol. 41, no. 8, pp. 1114–1121, 2003. @article{Harvey2003,Over the last decade a range of studies have shown that some patients with hemispatial neglect subjectively underestimate the size of objects presented in their contralesional hemispace. Recently, it has been suggested that the effect is simply due to either hemianopia [Brain 124 (2001) 527], or the combination of neglect and hemianopia [Neurology 52 (1999) 1845]. In the current study we asked right hemisphere lesioned patients with and without neglect and hemianopia as well as healthy controls to judge either two horizontal or vertical lines presented simultaneously in right and left hemispace and monitored their eye movements. Three out of the six patients showed the predicted size distortion effect for horizontal lines. We found no evidence that the effect was mediated by eye movements. The two neglect patients who showed the strongest left side underestimation showed symmetrical (left, right) scanning of the lines both in terms of number of fixations and fixation time, yet they still failed to judge the relative size veridically. In addition, we did not find strong evidence for a link with hemianopia. We therefore propose that the effect reflects a computational/representational failure of processing for horizontal extent. |
Toshihide Imaruoka; Toshio Yanagida; Satoru Miyauchi Attentional set for external information activates the right intraparietal area Journal Article In: Cognitive Brain Research, vol. 16, no. 2, pp. 199–209, 2003. @article{Imaruoka2003,Visual attention can be allocated to a location or an object by using two different types of information: internal information and external information. The results of recent psychological studies [Bagon and Egeth, Percept. Psychophys. 55 (1994) 485] suggest that an observer's attentional set determines how these two kinds of information are used in visual tasks. In this study, we measured brain activities during two modes of visual search; one is the feature search mode, in which an attentional set for knowledge of a target item (internal information) is used, and the other is the singleton detection mode, in which an attentional set for oddness in the visual scene (external information) is used. We found extended activation in the frontal and parietal areas for both search modes. In addition, a direct comparison of brain activity during the singleton detection mode and the feature search mode revealed that the areas around the right intraparietal sulcus were more involved in the attentional set for oddness. These results suggest that the human right intraparietal cortex is related to the attentional set for external information. |
Taosheng Liu; Scott D. Slotnick; John T. Serences; Steven Yantis Cortical mechanisms of feature-based attentional control Journal Article In: Cerebral Cortex, vol. 13, no. 12, pp. 1334–1343, 2003. @article{Liu2003,A network of fronto-parietal cortical areas is known to be involved in the control of visual attention, but the representational scope and specific function of these areas remains unclear. Recent neuroimaging evidence has revealed the existence of both transient (attention-shift) and sustained (attention-maintenance) mechanisms of space-based and object-based attentional control. Here we investigate the neural mechanisms of feature-based attentional control in human cortex using rapid event-related functional magnetic resonance imaging (fMRI). Subjects viewed an aperture containing moving dots in which dot color and direction of motion changed once per second. At any given moment, observers attended to either motion or color. Two of six motion directions and two of six colors embedded in the stimulus stream cued subjects either to shift attention from the currently attended to the unattended feature or to maintain attention on the currently attended feature. Attentional modulation of the blood oxygenation level dependent (BOLD) fMRI signal was observed in early visual areas that are selective for motion and color. More importantly, both transient and sustained BOLD activity patterns were observed in different fronto-parietal cortical areas during shifts of attention. We suggest these differing temporal profiles reflect complementary roles in the control of attention to perceptual features. |
Shinsuke Shimojo; Claudiu Simion; Eiko Shimojo; Christian Scheier Gaze bias both reflects and influences preference Journal Article In: Nature Neuroscience, vol. 6, no. 12, pp. 1317–1322, 2003. @article{ssss03,Emotions operate along the dimension of approach and aversion, and it is reasonable to assume that orienting behavior is intrinsically linked to emotionally involved processes such as preference decisions. Here we describe a gaze 'cascade effect' that was present when human observers were shown pairs of human faces and instructed to decide which face was more attractive. Their gaze was initially distributed evenly between the two stimuli, but then gradually shifted toward the face that they eventually chose. Gaze bias was significantly weaker in a face shape discrimination task. In a second series of experiments, manipulation of gaze duration, but not exposure duration alone, biased observers' preference decisions. We thus conclude that gaze is actively involved in preference formation. The gaze cascade effect was also present when participants compared abstract, unfamiliar shapes for attractiveness, suggesting that orienting and preference for objects in general are intrinsically linked in a positive feedback loop leading to the conscious choice. |
Albrecht W. Inhoff; Ralph Radach; Brianna M. Eiter; Barbara J. Juhasz Distinct subsystems for the parafoveal processing of spatial and linguistic information during eye fixations in reading Journal Article In: Quarterly Journal of Experimental Psychology, vol. 56A, no. 5, pp. 803–827, 2003. @article{Inhoff2003,Two experiments examined readers' use of parafoveally obtained word length information for word recognition. Both experiments manipulated the length (number of constituent characters) of a parafoveally previewed target word so that it was either accurately or inaccurately specified. In experiment 1, previews either revealed or denied useful orthographic information. In experiment 2, parafoveal targets were either high- or low-frequency words. Eye movement contingent display changes were used to show the intact target upon its fixation. Examination of target viewing duration showed completely additive effects of word length previews & of orthographic previews in experiment 1, viewing duration being shorter in the accurate-length & the orthographic preview conditions. Experiment 2 showed completely additive effects of word length & word frequency, target viewing being shorter in the accurate-length & the high-frequency conditions. Together, these results indicate that functionally distinct subsystems control the use of parafoveally visible spatial & linguistic information in reading. Parafoveally visible spatial information appears to be used for two distinct extralinguistic computations: visual object selection & saccade specification. |
Charissa R. Lansing; George W. McConkie Word identification and eye fixation locations in visual and visual-plus-auditory presentations of spoken sentences Journal Article In: Perception and Psychophysics, vol. 65, no. 4, pp. 536–552, 2003. @article{Lansing2003,In this study, we investigated where people look on talkers' faces as they try to understand what is being said. Sixteen young adults with normal hearing and demonstrated average speechreading proficiency were evaluated under two modality presentation conditions: vision only versus vision plus low-intensity sound. They were scored for the number of words correctly identified from 80 unconnected sentences spoken by two talkers. The results showed two competing tendencies: an eye primacy effect that draws the gaze to the talkers eyes during silence and an information source attraction effect that draws the gaze to the talker's mouth during speech periods. Dynamic shifts occur between eyes and mouth prior to speech onset and following the offset of speech, and saccades tend to be suppressed during speech periods. The degree to which the gaze is drawn to the mouth during speech and the degree to which saccadic activity is suppressed depend on the difficulty of the speech identification task. Under the most difficult modality presentation condition, vison only, accuracy was related to average sentence difficulty and individual proficiency in visual speech perception, but not to the proportion of gaze time directed toward the talkers mouth or toward other parts of the talker's face. |
Jan Theeuwes; Giel Jan De Vries; Richard Godijn Attentional and oculomotor capture with static singletons Journal Article In: Perception and Psychophysics, vol. 65, no. 5, pp. 735–746, 2003. @article{Theeuwes2003,Previous research has shown that in visual search static singletons have the ability to capture attention (Theeuwes, 1991a, 1992). The present study investigated whether these singletons also have the ability to capture the eyes. Participants had to make an eye movement and respond manually to a shape singleton while a color singleton was present. When participants searched for a unique shape while a unique color singleton was present there was strong attentional and oculomotor capture (Experiment 1). However, when participants searched for a specific-shape singleton (a green circle) when a specific-color singleton (a red element) had to be ignored, there was attentional capture but no oculomotor capture (Experiment 2). The results suggest that an attentional set for a specific feature value defining both the target and the distractor (as in Experiment 2) allows such a fast disengagement of attention from the location of the distractor that a saccade execution to that location is prevented. |
Katia Duscherer; Daniel Holender Semantic priming from flanker words: Some limitations to automaticity Journal Article In: Psychologica Belgica, vol. 43, no. 3, pp. 153–179, 2003. @article{Duscherer2003,We explore under which conditions words flanking a centrally presented digit in the prime display can elicit semantic priming on the lexical decision to a subsequent letter string appearing at fixation about 1 sec later. No significant priming is found when the prime display requires an immediate odd/even classification of a digit (Experiment 1), a delayed recall of a digit (Experiment 3), or the detection of an infrequent change from the digit 4 to the letter A (Experiment 4). It is only in Experiment 2, in which nothing is presented at fixation during the prime display in positive lexical decision trials, that a positive semantic priming effect is found. These results are discussed in the framework of quantitative and qualitative limitations to processing automaticity. |
2002 |
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 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{Gysen2002a,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. |
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{Gysen2002b,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. |
F. Møller; M. L. Laursen; J. Tygesen; A. K. Sjølie Binocular quantification and characterization of microsaccades Journal Article In: Graefe's Archive for Clinical and Experimental Ophthalmology, vol. 240, no. 9, pp. 765–770, 2002. @article{Moeller2002,BACKGROUND: The significance of microsaccades in the visual process has been discussed for more than 50 years. However, only a few studies have measured microsaccades binocularly, and detailed quantification and characterization of these small movements are needed in order to further understand their nature. METHOD: The amplitude, velocity, acceleration and direction of microsaccades were quantified binocularly in 10 normal test persons during a 40-s fixation task, using an infrared recording technique. RESULTS: All microsaccades for all test persons were performed simultaneously and individually with an almost identical amplitude in the right and left eye (a range of 0.003-0.042 deg between right and left eye mean values). The mean microsaccadic amplitude for the test persons was within a range of 0.223-1.079 deg. The directional difference between simultaneously-performed right and left eye microsaccades was less than 22.5 deg for 84.8% of the saccades, indicating that the majority of microsaccades are conjugated. Three different fixation patterns were identified and characterized: (1) a classic interplay between easily identified drifts and medium-sized microsaccades (mean amplitude range 0.328-0.413 deg); (2) long intersaccadic intervals (4-5 s) with almost absent drifts, followed by three or four large microsaccades (mean amplitude range 0.755-1.079 deg); and (3) low-amplitude drift movements interrupted by low-amplitude microsaccades (mean amplitude range 0.231-0.265 deg). CONCLUSION: Microsaccades are involuntary, predominantly conjugated, simultaneously performed, and of almost identical amplitude in the right and left eye, suggesting a central control mechanism for microsaccades at subcortical level. |
Paola Ricciardelli; Emanuela Bricolo; Salvatore M. Aglioti; Leonardo Chelazzi My eyes want to look where your eyes are looking: Exploring the tendency to imitate another individual's gaze Journal Article In: NeuroReport, vol. 13, no. 17, pp. 2259–2264, 2002. @article{rbac02,In this studyweinvestigated the tendencyofhumans toimitate the gaze direction of other individuals.Distracting gaze stimuli or non biological directional cues (arrows) were presented to observers performing an instructed saccadic eyemovement task. Eyemove- mentrecordings showed thatobserversperformedless accurately when the distracting gaze and the instructed saccade had opposite directions,with a substantial number of saccadesmatching the di- rection of the distracting gaze. Static (Experiment1) and dynamic (Experiment 2) gaze distracters, but not pointing arrows (Experiment 3), produced the e¡ect.Results showa strong predisposition of humans to imitate somebody else's oculomotor behaviour, even when detrimental to task performance. This is likely linked to a strong tendency to share attentional states of other individuals, known as joint attention. |
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. |
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. |
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. |
Timothy L. Hodgson; B. Tiesman; Adrian M. Owen; Christopher Kennard Abnormal gaze strategies during problem solving in Parkinson's disease Journal Article In: Neuropsychologia, vol. 40, no. 4, pp. 411–422, 2002. @article{Hodgson2002a,We have taken 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 task. Control subjects and patients with idiopathic Parkinson's disease (PDs) viewed a series of pictures depicting two arrangements of coloured balls in pockets within the upper and lower halves of a computer display. The task was to plan (but not 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 number of moves required for problem solution. As problem complexity increased, control subjects spent proportionally more time fixating the Workspace region. This pattern was found regardless of whether subjects were instructed to solve problems by rearranging balls in the lower or upper visual fields. The distribution of gaze within the Workspace was also found to be problem dependent, with gaze being selectively directed towards the problem critical balls. In contrast, PDs were found to make more errors in the task and failed to show any dissociation in the amount of time fixating the two halves of the display. This pattern suggests that the patients had difficulty in encoding and/or maintaining current goals during problem solving, consistent with a role for fronto-striatal circuits in mechanisms of working memory and attention. |
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. |
Michael D. Crossland; Gary S. Rubin The use of an infrared eyetracker to measure fixation stability Journal Article In: Optometry and Vision Science, vol. 79, no. 11, pp. 735–739, 2002. @article{Crossland2002,PURPOSE: To assess fixation stability in patients, a scanning laser ophthalmoscope (SLO) has typically been required. Disadvantages of this technique include the need for a fixed viewing distance and rigid head support. Some modern infrared eyetrackers do not have these constraints. The purpose of this study was to compare fixation stability measurements made with these instruments. METHODS: Normal subjects were asked to fixate a 2.5 degrees high cross while fixation was measured with a SLO and an infrared eyetracker. Bivariate contour ellipse areas were calculated. RESULTS: There was a linear relationship between the bivariate contour ellipse areas measured using each instrument. Bivariate contour ellipse areas returned from the eyetracker were larger. There was no difference in test-retest variability between the instruments. CONCLUSIONS: The eyetracker indicates fixation to be less stable than the SLO does, perhaps because of eye movements to compensate for small head movements. Our eyetracker can be used to analyze fixation when viewing images at any distance, without the need for head immobilization. The eyetracker and the SLO complement each other in the investigation of visual behavior. |
Sunila Jain; Frank A. Proudlock; Cris S. Constantinescu; Irene Gottlob Combined pharmacologic and surgical approach to acquired nystagmus due to multiple sclerosis Journal Article In: American Journal of Ophthalmology, vol. 134, no. 5, pp. 780–782, 2002. @article{Jain2002,PURPOSE: To describe a combined pharmacological and surgical approach to treating acquired nystagmus in a patient with multiple sclerosis. DESIGN: Interventional case report. METHODS: A 40-year-old patient with acquired horizontal and vertical nystagmus and severe oscillopsia secondary to multiple sclerosis had combined treatment with gabapentin and a vertical Kestenbaum-type procedure. RESULTS: After gabapentin treatment (3,000 mg orally daily) the horizontal nystagmus was significantly reduced, and the patient developed a marked chin-up position. The vertical nystagmus remained unchanged, dampening on downgaze. A recession of both inferior rectus muscles reduced the nystagmus significantly in primary position, the abnormal head position disappeared, and oscillopsia completely resolved. Treatment increased visual acuity from 6/24 in the right eye and 6/60 in the left eye to 6/9 in both eyes. CONCLUSIONS: Acquired nystagmus in multiple sclerosis can be significantly improved by using a combined pharmacological and surgical approach. |
Scott D. Slotnick; Joseph B. Hopfinger; Stanley A. Klein; Erich E. Sutter Darkness beyond the light: Attentional inhibition surrounding the classic spotlight Journal Article In: NeuroReport, vol. 13, no. 6, pp. 773–778, 2002. @article{shks02,The aim of the present investigation was to determine the nature and spatial distribution of selective visual attention. Using cortical source localization of ERP data corresponding to 60 task-irrelevant stimuli across the visual field, we assessed attention effects on visual processing. Consistent with previous findings, visual processing was enhanced at the attended spatial location. In addition, this facilitation of processing extended from the attended location to the point of fixation resulting in a region of facilitation. Furthermore, a large region of inhibition was found surrounding this region of facilitation. The latter result is inconsistent with a simple facilitative spotlight model of attention and indicates that attention effects can be both facilitatory and inhibitory. |
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. |
Tanja R. M. Coeckelbergh; Frans W. Cornelissen; Wiebo H. Brouwer; Aart C. Kooijman The effect of visual field defects on eye movements and practical fitness to drive Journal Article In: Vision Research, vol. 42, no. 5, pp. 669–677, 2002. @article{Coeckelbergh2002,Eye movements of subjects with visual field defects due to ocular pathology were monitored while performing a dot counting task and a visual search task. Subjects with peripheral field defects required more fixations, longer search times, made more errors, and had shorter fixation durations than control subjects. Subjects with central field defects performed less well than control subjects although no specific impairment could be pinpointed. In both groups a monotonous relationship was observed between the visual field impairment and eye movement parameters. The use of eye movement parameters to predict viewing behavior in a complex task (e.g. driving) was limited. |
Boris M. Velichkovsky; Sascha M. Dornhoefer; Mathias Kopf; Jens R. Helmert; Markus Joos Change detection and occlusion modes in road-traffic scenarios Journal Article In: Transportation Research Part F: Traffic Psychology and Behaviour, vol. 5, no. 2, pp. 99–109, 2002. @article{Velichkovsky2002,Change blindness phenomena are widely known in cognitive science, but their relation to driving is not quite clear. We report a study where subjects viewed colour video stills of natural traffic while eye movements were recorded. A change could occur randomly in three different occlusion modes-blinks, blanks and saccades-or during a fixation (as control condition). These changes could be either relevant or irrelevant with respect to the traffic safety. We used deletions as well as insertions of objects. All occlusion modes were equivalent concerning detection rate and reaction time, deviating from the control condition only. The detection of relevant changes was both more likely and faster than that of irrelevant ones, particularly for relevant insertions, which approached the base line level. Even in this case, it took about 180 ms longer to react to changes when they occurred during a saccade, blink or blank. In a second study, relevant insertions and the blank occlusion were used in a driving simulator environment. We found a surprising effect in the dynamic setting: an advantage in change detection rate and time with blanks compared to the control condition. Change detection was also good during blinks, but not in saccades. Possible explanation of these effects and their practical implications are discussed. |
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. |
Johanna K. Kaakinen; Jukka Hyönä; Janice M. Keenan Perspective effects on online text processing Journal Article In: Discourse Processes, vol. 33, no. 2, pp. 159–173, 2002. @article{Kaakinen2002,The effect of a reading perspective on online text processing was studied by recording readers' eye movements during reading. Participants read an expository text about 4 countries with the goal of deciding whether one of the countries, designated by the experimenter as the reading perspective, would be a good new place of residence. The results showed better memory for perspective-relevant information and longer fixation times on perspective-relevant information. Individual differences in working memory were assessed with the reading span test. Results showed that the time course of the perspective effect varied with memory span: High-span readers showed a perspective relevance effect on initial reading of the target segments, whereas low-span readers showed the effect only in the later look backs. |
Maarten A. Frens Scleral search coils influence saccade dynamics Journal Article In: Journal of Neurophysiology, vol. 88, no. 2, pp. 692–698, 2002. @article{Frens2002,The scleral search coil technique is commonly used for recording eye movements. The goal of this paper is to investigate to what extent the placement of scleral search coils onto the eyes influences the kinematics of saccades. To that end saccadic eye movements of human subjects were recorded with an infrared video system, while they wore coils and we compared the main sequence properties with recordings in which no coils were mounted on the eyes. It was found that saccades last longer (by about 8%) and become slower (by about 5%) when both eyes wear coils. This is truly due to the fact that the coils are on the eyes and not due to other factors that are part of this method, such as the scleral anesthesia. The influence of coils in both eyes was also observed when one coil was mounted on one eye only. Therefore the effect that the coils have on the eye movements cannot be attributed to purely mechanical factors, such as inertial load on the eyeball or increased friction. Rather the coils appear to change the oculomotor command signals that drive the saccadic eye movements. |
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 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. |
Charles A. Collin; Avi Chaudhuri Using MATLAB with the Psychophysics Toolbox to present the heterochromatic fusion nystagmus stimulus Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 34, no. 4, pp. 500–508, 2002. @article{Collin2002,We present a program for MATLAB that generates and presents the heterochromatic fusion nystagmus stimulus. This stimulus allows assessment of isoluminant states through recordings of reflexive eye movements (optokinetic nystagmus). The reflexive nature of the subject's response makes this stimulus especially useful with nonverbal subjects, such as children and animals. Unfortunately, the stimulus is complex and difficult to program. By presenting the present program, we hope to help those who wish to use this tool in their research. The code of the function can be downloaded at www. dal.ca/-mcmullen/downloads.html. |
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. |
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. |
M. L. M. Tant; Frans W. Cornelissen; Aart C. Kooijman; Wiebo H. Brouwer Hemianopic visual field defects elicit hemianopic scanning Journal Article In: Vision Research, vol. 42, no. 10, pp. 1339–1348, 2002. @article{Tant2002,Previous explanations for the variability in success of compensating for homonymous hemianopia (HH) has been in terms of extent of the brain injury. In using on-line eye movement registrations, we simulated HH in 16 healthy subjects and compared their scanning performance on a dot counting task to their own "normal" condition and to real HH patients' performance. We evidenced clear parallels between simulated and real HH, suggesting that hemianopic scanning behaviour is primarily visually elicited, namely by the visual field defect, and not by the additional brain damage. We further observed age-related processes in compensating for the HH. |
M. C. Doyle; Robin Walker Multisensory interactions in saccade target selection: Curved saccade trajectories Journal Article In: Experimental Brain Research, vol. 142, no. 1, pp. 116–130, 2002. @article{Doyle2002,In a series of experiments, we examined the change in saccade trajectories observed when distractors are presented at non-target locations. The primary aim of the experiments was to examine multisensory interaction effects between the visual, auditory and somatosensory modalities in saccade generation. In each experiment observers made saccades to visual targets above and below fixation in the presence of visual, auditory or tactile stimuli to the left or right of fixation. In experiment 1 distractor location indicated which of two stimuli was the target for the saccade. Saccade trajectories showed strong leftward curvature following right-side distractors and showed rightward curvature following left-side distractors. The largest effects on trajectories were observed for visual distractors, but significant curvature was observed with auditory and somatosensory distractors. In experiment 2 saccades were made following the onset of a visual target (reflexive) or following presentation of an arrow at fixation (voluntary), and task-irrelevant crossmodal distractors were presented simultaneously with target onset. Both voluntary and reflexive saccades were found to curve away from task-irrelevant visual distractors, but auditory and somatosensory distractors did not modulate saccade trajectories. In experiment 3 task-irrelevant distractors preceded the onset of the target by 100 ms. Reflexive saccades were found to curve away from visual, auditory and somatosensory distractors, but voluntary saccades curved away from visual distractors only. The modulation of saccade trajectories by distractors from different modalities is interpreted in terms of inhibitory processes operating in neural structures involved in saccade generation. Our findings suggest that visual, auditory and somatosensory distractors can all modulate saccade trajectories. Such effects could be related to the inhibition of populations of neurons, in a common motor map, for the selection of a saccade target. |
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. |
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 Measuring saccade curvature: A curve-fitting approach Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 34, no. 4, pp. 618–624, 2002. @article{Ludwig2002,Saccade curvature is becoming a popular measure for detecting the presence of competing saccadic motor programs. Several different methods of quantifying saccade curvature have been employed. In the present study, we compared these metrics with each other and with novel measures based on curve fitting. Initial deviation metrics were only moderately associated with the more widely used metric of maximum curvature. The latter was strongly related to a recently developed area-based measure and to the novel methods based on second- and third-order polynomial fits. The curve-fitting methods showed that although most saccades curved in only one direction, there was a population of trajectories with both a maximum and a minimum (i.e., double-curved saccades). We argue that a curvature metric based on a quadratic polynomial fit deals effectively with both types of trajectories and, because it is based on all the samples of a saccade, is less susceptible to sampling noise. |
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. |
Elliot M. Frohman; Teresa C. Frohman; Padraig O'Suilleabhain; H. Zhang; K. Hawker; M. K. Racke; W. Frawley; J. T. Phillips; Phillip D. Kramer Quantitative oculographic characterisation of internuclear ophthalmoparesis in multiple sclerosis: The versional dysconjugacy index Z score Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 73, pp. 51–55, 2002. @article{Frohman2002,Background: There is a poor correlation between multiple sclerosis disease activity, as measured by magnetic resonance imaging, and clinical disability. Objective: To establish oculographic criteria for the diagnosis and severity of internuclear ophthalmoparesis (INO), so that future studies can link the severity of ocular dysconjugacy with neuro- radiological abnormalities within the dorsomedial brain stem tegmentum. Methods: The study involved 58 patients with multiple sclerosis and chronic INO and 40 normal sub- jects. Two dimensional infrared oculography was used to derive the versional dysconjugacy index (VDI)—the ratio of abducting to adducting eye movements for peak velocity and acceleration. Diagnostic criteria for the diagnosis and severity of INO were derived using a Z score and histogram analysis, which allowed comparisons of the VDI from multiple sclerosis patients and from a control population. Results: For a given saccade, the VDI was typically higher for acceleration v velocity, whereas the Z scores for velocity measures were always higher than values derived from comparable acceleration VDI measures; this was related to the greater variability of acceleration measures. Thus velocity was a more reliable measure from which to determine Z scores and thereby the criteria for INO and its level of severity. The mean (SD) value of the VDI velocity derived from 40 control subjects was 0.922 (0.072). The highest VDI for velocity from a normal control subject was 1.09, which was 2.33 SD above the normal control mean VDI. We therefore chose 2 SD beyond this value (that is, a Z score of 4.33) as the minimum criterion for the oculographic confirmation of INO. Of patients thought to have unilateral INO on clinical grounds, 70% (16/23) were found to have bilateral INO on oculographic assessment. Conclusions: INO can be confirmed and characterised by level of severity using Z score analysis of quantitative oculography. Such assessments may be useful for linking the level of severity of a specific clinical disability with neuroradiological measures of brain tissue pathology in multiple sclerosis. I |
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. |
Bettina Olk; Monika Harvey; Iain D. Gilchrist First saccades reveal biases in recovered neglect Journal Article In: Neurocase, vol. 8, no. 4, pp. 306–313, 2002. @article{Olk2002,Hemispatial neglect affects the ability to explore space on the side opposite a brain lesion. This deficit is also mirrored in abnormal saccadic eye movement patterns. The present study investigated if the recovery of neglect is also reflected in saccadic eye movements. Patient AF, who displayed strong hemispatial neglect 1 month post-right thalamic stroke, had largely recovered 3 months later when tested on visual exploration tasks of the Behavioural Inattention Test. At this stage, AF was tested on a visual search task while his eye movements (direction, latencies and amplitudes of first saccades) and manual reaction times were recorded. The experimental conditions differed with respect to stimulus number and distracter type and increased in difficulty. AF correctly generated saccades into the neglected field when the target was presented alone. In contrast, a considerable left/right difference was present for all multiple-stimulus search displays. Although recovered from neglect in standardized assessment, AF showed a strong rightward bias resulting in highly asymmetric response times and eye movement behaviour. We conclude that eye movement patterns are far more susceptible to remaining spatial impairments and can thus provide a sensitive means to assess the extent of neglect recovery. |
Dale J. Barr; Boaz Keysar Anchoring comprehension in linguistic precedents Journal Article In: Journal of Memory and Language, vol. 46, no. 2, pp. 391–418, 2002. @article{Barr2002,Past research has shown that when speakers refer to the same referent multiple times, they tend to standardize their descriptions by establishing linguistic precedents. In three experiments, we show that listeners reduce uncertainty in comprehension by taking advantage of these precedents. We tracked listeners' eye movements in a referential communication task and found that listeners identified referents more quickly when specific precedents existed than when there were none. Furthermore, we found that listeners expected speakers to adhere to precedents even in contexts where it would lead to referential overspecification. Finally, we provide evidence that the benefits of linguistic precedents are independent of mutual knowledge - listeners were not more likely to benefit from precedents when they were mutually known than when they were not. We conclude that listeners use precedents simply because they are available, not because they are mutually known. |
David A. Leopold; Holger K. Plettenberg; Nikos K. Logothetis Visual processing in the ketamine-anesthetized monkey: Optokinetic and blood oxygenation level-dependent responses Journal Article In: Experimental Brain Research, vol. 143, no. 3, pp. 359–372, 2002. @article{Leopold2002,We used optokinetic responses and functional magnetic resonance imaging (fMRI) to examine visual processing in monkeys whose conscious state was modulated by low doses (1-2 mg/kg) of the dissociative anesthetic ketamine. We found that, despite the animal's dissociated state and despite specific influences of ketamine on the oculomotor system, optokinetic nystagmus (OKN) could be reliably elicited with large, moving visual patterns. Responses were horizontally bidirectional for monocular stimulation, indicating that ketamine did not eliminate cortical processing of the motion stimulus. Also, results from fMRI directly demonstrated that the cortical blood oxygenation level-dependent (BOLD) response to visual patterns was preserved at the same ketamine doses used to elicit OKN. Finally, in the ketamine-anesthetized state, perceptually bistable motion stimuli produced patterns of spontaneously alternating OKN that normally would be tightly coupled to perceptual changes. These results, taken together, demonstrate that after ketamine administration cortical circuits continue to processes visual patterns in a dose-dependent manner despite the animal's behavioral dissociation. While perceptual experience is difficult to evaluate under these conditions, oculomotor patterns revealed that the brain not only registers but also acts upon its sensory input, employing it to drive a sensorimotor loop and even responding to a sensory conflict by engaging in spontaneous perception-related state changes. The ketamine-anesthetized monkey preparation thereby offers a safe and viable paradigm for the behavioral and electrophysiological investigation of issues related to conscious perception and anesthesia, as well as neural mechanisms of basic sensory processing. |
Sonja Stork; Sebastiaan F. W. Neggers; Jochen Müsseler Intentionally-evoked modulations of smooth pursuit eye movements Journal Article In: Human Movement Science, vol. 21, no. 3, pp. 335–348, 2002. @article{Stork2002,When observers pursue a moving target with their eyes, they use predictions of future target positions in order to keep the target within the fovea. It was suggested that these predictions of smooth pursuit (SP) eye movements are computed only from the visual feedback of the target characteristics. As a consequence, if the target vanishes unexpectedly, the eye movements do not stop immediately, but they overshoot the vanishing point. We compared the spatial and temporal features of such predictive eye movements in a task with or without intentional control over the target vanishing point. If the observers stopped the target with a button press, the overshoot of the eyes was reduced compared to a condition where the offset was computer generated. Accordingly, the eyes started to decelerate well before the target offset and lagged further behind the target when it disappeared. The involvement of intentionally-generated expectancies in eye movement control was also obvious in the spatial trajectories of the eyes, which showed a clear flexion in anticipation of the circular motion path we used. These findings are discussed together with neurophysiological mechanisms underlying the SP eye movements. |
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. |
Richard Godijn; Jan Theeuwes Programming of exogenous and endogenous saccades: Evidence for a competitive integration model Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 28, pp. 1039–1054, 2002. @article{Godijn2002,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 |
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. |
Bob McMurray; Michael K. Tanenhaus; Richard N. Aslin Gradient effects of within-category phonetic variation on lexical access Journal Article In: Cognition, vol. 86, no. 2, pp. B33–B42, 2002. @article{McMurray2002,In order to determine whether small within-category differences in voice onset time (VOT) affect lexical access, eye movements were monitored as participants indicated which of four pictures was named by spoken stimuli that varied along a 0-40 ms VOT continuum. Within-category differences in VOT resulted in gradient increases in fixations to cross-boundary lexical competitors as VOT approached the category boundary. Thus, fine-grained acoustic/phonetic differences are preserved in patterns of lexical activation for competing lexical candidates and could be used to maximize the efficiency of on-line word recognition. |
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. |
Jukka Hyönä; Robert F. Lorch; Johanna K. Kaakinen Individual differences in reading to summarize expository text: Evidence from eye fixation patterns. Journal Article In: Journal of Educational Psychology, vol. 94, no. 1, pp. 44–55, 2002. @article{Hyoenae2002,Eye fixation patterns were used to identify reading strategies of adults as they read multiple-topic expository texts. A clustering technique distinguished 4 strategies that differed with respect to the ways in which readers reprocessed text. The processing of fast linear readers was characterized by the absence of fixations returning to previous text. Slow linear readers made lots of forward fixations and reinspected each sentence before moving to the next. The reading of nonselective reviewers was characterized by look backs to previous sentences. The distinctive feature of topic structure processors was that they paid close attention to headings. They also had the largest working-memory capacity and wrote the most accurate text summaries. Thus, qualitatively distinct reading strategies are observable among competent, adult readers. |
Jukka Hyönä; Seppo Vainio; Matti Laine A morphological effect obtains for isolated words but not for words in sentence context Journal Article In: European Journal of Cognitive Psychology, vol. 14, no. 4, pp. 417–433, 2002. @article{Hyoenae2002a,The effect of morphological complexity on word identification was studied in three experiments conducted in Finnish, employing the same set of target nouns. In Experiment 1, the target nouns were presented in isolation, and lexical decision times were employed as lexical access measures. In Experiments 2 and 3, the same words$backslash$nwere embedded in sentence contexts, where both the inflected and non-inflected forms were equally plausible, and eye fixation patterns (Exp. 2) and lexical decision latencies (Exp. 3) were recorded. The experiment with isolated words replicated previous lexical decision studies by showing more effortful processing for inflected than monomorphemic nouns. However, this morphological complexity effect did not generalise to the context experiments; fixation durations and response latencies were highly similar for inflected and monomorphemic words. It is suggested that, at least for the type of inflected nouns studied,$backslash$nthe morphological effect observed for isolated words may derive from the syntactic and/or semantic level and not necessarily from the lexical level, as previously assumed. |
Timothy Desmet; Constantijn De Baecke; Marc Brysbaert The influence of referential discourse context on modifier attachment in Dutch Journal Article In: Memory & Cognition, vol. 30, no. 1, pp. 150–157, 2002. @article{Desmet2002,In an eye-tracking experiment we investigated the influence of referential context on the attachment of a relative clause to two possible hosts (as in "Someone shot the servant of the actress who was on the balcony"). The attachment of the relative clause was disambiguated grammatically at the first word after the onset of the ambiguity in order to investigate immediate effects of discourse. The contexts had been verified in a sentence completion study to make sure that they induced a strong bias toward early or late closure. The results of the reading experiment, however, revealed no significant interaction of referential context with the attachment preference of the relative clause. The only robust and consistent effect we found was a preference for early closure, independent of the preceding context. These data favor accounts positing that referential context does not influence the initial attachment decision, but does play a role in later phases of sentence processing. |
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. |
Frans W. Cornelissen; Enno M. Peters; John Palmer The Eyelink Toolbox: Eye tracking with MATLAB and the Psychophysics Toolbox Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 34, no. 4, pp. 613–617, 2002. @article{Cornelissen2002,The Eyelink Toolbox software supports the measurement of eye movements. The toolbox provides an interface between a high-level interpreted language (MATLAB), a visual display programming tool- box (Psychophysics Toolbox), and a video-based eyetracker (Eyelink). The Eyelink Toolbox enables experimenters to measure eye movements while simultaneously executing the stimulus presentation routines provided by the Psychophysics Toolbox. Example programs are included with the toolbox distribution. Information on the Eyelink Toolbox can be found at http://psychtoolbox.org/. |
Frank A. Proudlock; Irene Gottlob; Cris S. Constantinescu Oscillopsia without nystagmus caused by head titubation in a patient with multiple sclerosis Journal Article In: Journal of Neuro-Ophthalmology, vol. 22, no. 2, pp. 88–91, 2002. @article{Proudlock2002,Oscillopsia in patients who have brain stem disorders but not nystagmus is attributed to a failure of the vestibular-ocular reflex (VOR) to compensate for head movements. We report a patient who had marked head titubation and oscillopsia in aggressive multiple sclerosis but no nystagmus. Her severe head titubation precluded our ability to measure a VOR accurately. Because oscillopsia has also been described after rapid voluntary head oscillations in normal subjects, we queried whether the oscillopsia in our patient could be ascribed to the head movement alone. Six normal control subjects did not experience oscillopsia while shaking their heads at the same frequency as the patient's titubation. We conclude that the oscillopsia in our patient was probably the result of an impaired VOR or an alternative compensatory mechanism. |
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{Li2002,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. |
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{Li2002a,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. |
Monika Harvey; Bettina Olk; Keith Muir; Iain D. Gilchrist Manual responses and saccades in chronic and recovered hemispatial neglect: A study using visual search Journal Article In: Neuropsychologia, vol. 40, no. 7, pp. 705–717, 2002. @article{Harvey2002,Hemispatial neglect affects both the ability to respond to targets on the contralesional side of space and to programme saccades to such targets. In the current study, we looked in detail at saccade programming and manual reaction times (RTs) in a range of visual search tasks, in which task difficulty was systematically increased by changing the nature of the distractors. In condition 1, the target was presented with no distractors. In the other conditions, displays contained three distractors that were changed across conditions to manipulate similarity to the target and so task difficulty. We tested two neglect patients, one chronic, one recovered along with two RCVA control patients and 12 age-matched controls. Both neglect patients studied could successfully execute saccades into the neglected field when the target was presented alone. However, a dissociation emerged between the two patients when the target was presented with distractor items. Patient ERs first saccade to target performance in the three search conditions revealed clear effects of distractor type. In contrast for the recovered patient AF, the left/right difference was present for all search displays and appeared to be constant regardless of distractor type. This differential pattern of behaviour may reflect the different underlying neural causes of the neglect in these patients. In the current study, the measurement of saccades allowed the task to be fractionated, and thus, reveal the action of multiple mechanisms controlling saccades in search. |
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. |
Albrecht W. Inhoff; Cynthia M. Connine; Ralph Radach A contingent speech technique in eye movement research on reading Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 34, no. 4, pp. 471–480, 2002. @article{Inhoff2002,A novel eye-movement-contingent method is presented. It builds on and extends established eye-movement-contingent visual display change methods in that it uses movements of the eyes to control the presentation of acoustic information during sentence reading. In one implementation, an irrelevant spoken word is presented when the eyes cross a predetermined spatial boundary before they move on to a selected visual target word. The relationship between the spoken word and the visual target is manipulated, and the pattern of interference, caused by the presentation of the spoken word, is used to determine the nature and time course of activated representations. Results from three recently completed experiments in which the technique was used show that a word's phonological code remains active after it has been read and that the activated code has speech-like properties. |
Eyal M. Reingold On the perceptual specificity of memory representations Journal Article In: Memory, vol. 10, no. 5-6, pp. 365–379, 2002. @article{r02,The present paradigm involved manipulating the congruency of the perceptual processing during the study and test phases of a recognition memory task. During each trial, a gaze-contingent window was used to limit the stimulus display to a region either inside or outside a 10 degrees square centred on the participant's point of gaze, constituting the Central and Peripheral viewing modes respectively. The window position changed in real time in concert with changes in gaze position. Four experiments documented better task performance when viewing modes at encoding and retrieval matched than when they mismatched (i.e., perceptual specificity effects). Viewing mode congruency effects were demonstrated with both verbal and non-verbal stimuli. The present research is motivated and discussed in terms of theoretical views proposed in the 1970s including the levels-of-processing framework and the proceduralist viewpoint. In addition, implications for current processing and multiple systems views of memory are outlined. |
Hyung-Chul O. Li; Eli Brenner; Frans W. Cornelissen; Eun-Soo Kim Systematic distortion of perceived 2D shape during smooth pursuit eye movements Journal Article In: Vision Research, vol. 42, no. 23, pp. 2569–2575, 2002. @article{Li2002b,Even when the retinal image of a static scene is constantly shifting, as occurs when the viewer pursues a small moving object with his or her eyes, the scene is usually correctly perceived to be static. Following early suggestions by von Helmholtz, it is commonly believed that this spatial stability is achieved by combining retinal and extra-retinal signals. Here, we report a perceptually salient 2D shape distortion that can arise during pursuit. We provide evidence that the perceived 2D shape reflects retinal image contents alone, implying that the extra-retinal signal is ignored when judging 2D shape. © 2002 Elsevier Science Ltd. All rights reserved. |
Eyal M. Reingold; Lester C. Loschky Saliency of peripheral targets in gaze-contingent multiresolutional displays Journal Article In: Behavior Research Methods, Instruments & Computers, vol. 34, no. 4, pp. 491–499, 2002. @article{rl02,Gaze-contingent multiresolutional displays (GCMRDs) have been proposed to solve the processing and bandwidth bottleneck in many single-user displays, by dynamically placing high-resolution in a window at the center of gaze, with lower resolution everywhere else. The three experiments reported here document a slowing of peripheral target acquisition associated with the presence of a gaze-contingent window. This window effect was shown for displays using either moving video or still images. The win- dow effect was similar across a resolution-defined window condition and a luminance-defined window condition, suggesting that peripheral image degradation is not a prerequisite of this effect. The window effect was also unaffected by the type of window boundary used (sharp or blended). These results are interpreted in terms of an attentional bias resulting in a reduced saliency of peripheral targets due to increased competition from items within the window. We discuss the implications of the window effect for the study of natural scene perception and for human factors research related to GCMRDs. |
Eyal M. Reingold; Dave M. Stampe Saccadic inhibition in voluntary and reflexive saccades Journal Article In: Journal of Cognitive Neuroscience, vol. 14, no. 3, pp. 371–388, 2002. @article{rs02,The present study investigated saccadic inhibition in both voluntary and stimulus-elicited saccades. Two experiments examined saccadic inhibition caused by an irrelevant flash occurring subsequent to target onset. In each trial, participants were required to perform a single saccade following the presentation of a black target on a gray background, 4 degrees to the left or to the right of screen center. In some trials (flash trials), after a variable delay, a 33-msec flash was displayed at the top and bottom third of the monitor (these regions turned white). In all experimental conditions, histograms of flash-to-saccade latencies documented a decrease in saccadic frequency, forming a dip, time-locked to the flash and occurring as early as 60-70 msec following its onset. The fast latency of this effect strongly suggests a low-level, reflex-like, oculomotor effect, which was referred to as saccadic inhibition. A novel procedure was developed to allow comparisons of saccadic inhibition even across conditions, which in the absence of a flash (no-flash trials) produce dissimilar saccadic reaction times (SRTs) distributions. Experiment 1 examined the effects of the fixation stimulus on saccadic inhibition by contrasting three conditions: a gap condition (fixation stimulus disappeared 200 msec prior to target onset), a step condition (offset of the fixation stimulus was simultaneous with target onset), and an overlap condition (the fixation stimulus remained on for the duration of the trial). The overlap condition produced substantially stronger saccadic inhibition, relative to the gap and the step conditions. Experiment 2 contrasted the saccadic inhibition effect obtained for prosaccades (saccades aimed at the target) with the effect obtained for antisaccades (i.e., saccades aimed away from the same target). The onset of saccadic inhibition was earlier, and its magnitude was stronger, for antisaccades, relative to prosaccades. The plausibility that the superior colliculus is the neurophysiological locus of the saccadic inhibition effect was explored. |
2001 |
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. |
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. |
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. |
Risto Näsänen; Jan Karlsson; Helena Ojanpää Display quality and the speed of visual letter search Journal Article In: Displays, vol. 22, no. 4, pp. 107–113, 2001. @article{Naesaenen2001,Previously it has been suggested that visual search tasks can be used to evaluate the perceptual quality of display devices with respect to their ability to convey alphanumeric information. The purpose of the present study was to examine how character size and contrast used in a visual search test affects its sensitivity to differences in the quality of display devices. 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, that is, 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 fast video eye tracker. Threshold search times were measured as a function of character size at two contrast levels using a CRT and an LCD display. For all experimental conditions, threshold search time decreased with increasing letter size. This was accompanied with a decrease in the number of eye fixations per search as well as a decrease of fixation duration. At high contrast (CMichelson≈ 1), no statistically significant difference was found between the two displays. However, at the lower contrast used (CMichelson≈ 0.2) and at small character sizes, threshold search times for the CRT display were clearly longer and the number of fixations per search was higher than for the LCD display. In conclusion, visual letter search is a more sensitive method for display evaluation at small contrasts and with small character sizes. |
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. |
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{Pomplun2001,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. |
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{Pomplun2001a,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. |
Gary Feng; Kevin Miller; Hua Shu; Houcan Zhang Rowed to recovery: The use of phonological and orthographic information in reading Chinese and English Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 27, no. 4, pp. 1079–1100, 2001. @article{Feng2001,To examine how readers of Chinese and English take advantage of orthographic and phonological features in reading, the authors investigated the effects of spelling errors on reading text in Chinese and English using the error disruption paradigm of M. Daneman and E. Reingold (1993). Skilled readers in China and the United States read passages in their native language that contained occasional spelling errors. Results showed that under some circumstances very early phonological activation can be identified in English, but no evidence for early phonology was found in Chinese. In both languages, homophone errors showed a benefit in measures of later processing, suggesting that phonology helps readers recover from the disruptive effects of errors. These results suggest that skilled readers take advantage of the special features of particular orthographies but that these orthographic effects may be most pronounced in the early stages of lexical access. |
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{Greene2001,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. |
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{Greene2001a,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). |
Sebastian Pannasch; Sascha M. Dornhoefer; Pieter J. A. Unema; Boris M. Velichkovsky The omnipresent prolongation of visual fixations: Saccades are inhibited by changes in situation and in subject's activity Journal Article In: Vision Research, vol. 41, no. 25-26, pp. 3345–3351, 2001. @article{Pannasch2001,Presenting a distractor prolongs not only saccadic reaction times in paced tasks but also fixation durations in unpaced tasks. To investigate whether the effect of a distractor is a pure optomotor reflex, we used both visual and auditory distractors in an unpaced picture-viewing paradigm. Results show a distractor effect for both modalities. Analysis of data from previous studies showed similar effects, even in amodal shifts of attention. These findings challenge the hypothesis that the effect is modality-specific and suggest that the distractor effect may be another expression of the orienting reflex. |