All EyeLink Publications
All 12,000+ peer-reviewed EyeLink research publications up until 2023 (with some early 2024s) 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!
2004 |
T. M. Blekher; Robert D. Yee; S. C. Kirkwood; A. M. Hake; J. C. Stout; Marjorie R. Weaver; Tatiana M. Foroud Oculomotor control in asymptomatic and recently diagnosed individuals with the genetic marker for Huntington's disease Journal Article In: Vision Research, vol. 44, no. 23, pp. 2729–2736, 2004. @article{Blekher2004, We compared oculomotor control among individuals in the early stages of Huntington’s disease (HD), with that of individuals who are presymptomatic HD gene carriers (PSGC) and nongene carriers (NGC). The oculomotor testing paradigm included both traditional tests and a novel experimental procedure to assess visual scanning. Traditional tests elicited saccades, pursuit and optokinetic nystagmus (OKN). HD patients demonstrated marked delay in the initiation of volitional saccades (anti-saccade and memory-guided saccades), a reduced number of correct volitional saccades, reduced velocity of saccades, and a decreased OKN gain. We also studied visual scanning while the participants completed the Digit Symbol Subscale of the Wechsler Adult Intelligence Survey-Revised (WAIS-R). The HD participants demonstrated an abnormal gaze strategy, which may be associated with attention and/or planning deficits.Differences between the PSGC and NGC groups were only observed for two measures: PSGC had a decreased number of memory-guided saccades and a subtle delay in the initiation of volitional saccades. Our results suggest that oculomotor measures are a sensitive biomarker in the early stage of HD and demonstrate that the combination of more traditional oculomotor tests with visual scanning tests is useful in the evaluation of visual performance. © 2004 Elsevier Ltd. All rights reserved. |
Agnieszka Bojko; Arthur F. Kramer; Matthew S. Peterson Age equivalence in switch costs for prosaccade and antisaccade tasks Journal Article In: Psychology and Aging, vol. 19, no. 1, pp. 226–234, 2004. @article{Bojko2004, This study examined age differences in task switching using prosaccade and antisaccade tasks. Significant specific and general switch costs were found for both young and old adults, suggesting the existence of 2 types of processes: those responsible for activation of the currently relevant task set and deactivation of the previously relevant task set and those responsible for maintaining more than 1 task active in working memory. Contrary to the findings of previous research, which used manual response tasks with arbitrary stimulus-response mappings to study task-switching performance, no age-related deficits in either type of switch costs were found. These data suggest age-related sparing of task-switching processes in situations in which memory load is low and stimulus-response mappings are well learned. |
Walter R. Boot; Jason S. McCarley; Arthur F. Kramer; Matthew S. Peterson Automatic and intentional memory processes in visual search Journal Article In: Psychonomic Bulletin & Review, vol. 11, no. 5, pp. 854–861, 2004. @article{Boot2004, Previous research has indicated that saccade target selection during visual search is influenced by scanning history. Already inspected items are less likely to be chosen as saccade targets as long as the number intervening saccades is small. Here, we adapted Jacoby's (1991) process dissociation procedure to assess the role of intentional and automatic processes in saccade target selection. Results indicate a large automatic component biasing participants to move their eyes to unexamined locations. However, an intentional component allowed participants to both reinspect old items and aid their selection of new items. A second experiment examined inhibition of return (IOR) as a candidate for the observed automatic component. IOR was found for items that had been previously examined. It is concluded that both automatic and intentional memory traces are available to guide the eyes during search. |
Raymond Bertram; Alexander Pollatsek; Jukka Hyönä Morphological parsing and the use of segmentation cues in reading Finnish compounds Journal Article In: Journal of Memory and Language, vol. 51, no. 3, pp. 325–345, 2004. @article{Bertram2004, This eye movement study investigated the use of two types of segmentation cues in processing long Finnish compounds. The cues were related to the vowel quality properties of the constituents and properties of the consonant starting the second constituent. In Finnish, front vowels never appear with back vowels in a lexeme, but different quality vowels can appear in different constituents in compounds. Experiments 1 and 2 showed that compounds with different vowel quality constituents are processed faster than those with same vowel quality constituents, but only if the first constituent is long. This indicates that the use of segmentation cues in processing long compounds depends on the ease of encoding the first constituent. Experiment 3 established that (a) the effect does not depend on the crucial vowels being adjacent and (b) processing is affected by the type of consonant beginning the second constituent (i.e., whether or not it could end a first constituent). |
Christian F. Altmann; Arne Deubelius; Zoe Kourtzi Shape saliency modulates contextual processing in the human lateral occipital complex Journal Article In: Journal of Cognitive Neuroscience, vol. 16, no. 5, pp. 794–804, 2004. @article{Altmann2004, Visual context influences our perception of target objects in natural scenes. However, little is known about the analysis of context information and its role in shape perception in the human brain. We investigated whether the human lateral occipital complex (LOC), known to be involved in the visual analysis of shapes, also processes information about the context of shapes within cluttered scenes. We employed an fMRI adaptation paradigm in which fMRI responses are lower for two identical than for two different stimuli presented consecutively. The stimuli consisted of closed target contours defined by aligned Gabor elements embedded in a background of randomly oriented Gabors. We measured fMRI adaptation in the LOC across changes in the context of the target shapes by manipulating the position and orientation of the background elements. No adaptation was observed across context changes when the background elements were presented in the same plane as the target elements. However, adaptation was observed when the grouping of the target elements was enhanced in a bottom-up (i.e., grouping by disparity or motion) or top-down (i.e., shape priming) manner and thus the saliency of the target shape increased. These findings suggest that the LOC processes information not only about shapes, but also about their context. This processing of context information in the LOC is modulated by figure-ground segmentation and grouping processes. That is, neural populations in the LOC encode context information when relevant to the perception of target shapes, but represent salient targets independent of context changes. |
Gerry T. M. Altmann Language-mediated eye movements in the absence of a visual world: The 'blank screen paradigm' Journal Article In: Cognition, vol. 93, no. 2, pp. B79–87, 2004. @article{Altmann2004a, The 'visual world paradigm' typically involves presenting participants with a visual scene and recording eye movements as they either hear an instruction to manipulate objects in the scene or as they listen to a description of what may happen to those objects. In this study, participants heard each target sentence only after the corresponding visual scene had been displayed and then removed. For a scene depicting a man, a woman, a cake, and a newspaper, the eyes were subsequently directed, during 'eat' in 'the man will eat the cake', towards where the cake had previously been located even though the screen had been blank for over 2 s. The rapidity of these movements mirrored the anticipatory eye movements observed in previous studies [Cognition 73 (1999) 247; J. Mem. Lang. 49 (2003) 133]. Thus, anticipatory eye movements are not dependent on a concurrent visual scene, but are dependent on a mental record of the scene that is independent of whether the visual scene is still present. |
Sally Andrews; Brett Miller; Keith Rayner Eye movements and morphological segmentation of compound words: There is a mouse in mousetrap Journal Article In: European Journal of Cognitive Psychology, vol. 16, no. 1-2, pp. 285–311, 2004. @article{Andrews2004, In two experiments, readers' eye movements were monitored as they read sentences containing compound words. In Experiment 1, the frequency of the first and second morpheme was manipulated in compound words of low whole word frequency. Experiment 2 compared pairs of low frequency compounds with high and low frequency first morphemes but identical second morphemes that were embedded in the same sentence frames. The results showed significant effects of the frequency of both morphemes on gaze duration and total fixation time on the compound words. Regression analyses revealed an influence of whole word frequency on the same measures. The results suggest that morphemic constituents of compound words are activated in the course of retrieving the representation of the whole compound word. The fact that the frequency effects were not confined to fixations on the morphemic constituents themselves implies that saccadic eye movements are implemented before morphemic retrieval has been completed. The results highlight the importance of developing more precise models of the perceptual processes underlying reading and how they interact with the processes involved in lexical retrieval and comprehension. |
Andrew P. Bayliss; Giuseppe Di Pellegrino; Steven P. Tipper Orienting of attention via observed eye gaze is head-centred Journal Article In: Cognition, vol. 94, no. 1, pp. B1–B10, 2004. @article{Bayliss2004, Observing averted eye gaze results in the automatic allocation of attention to the gazed-at location. The role of the orientation of the face that produces the gaze cue was investigated. The eyes in the face could look left or right in a head-centred frame, but the face itself could be oriented 90 degrees clockwise or anticlockwise such that the eyes were gazing up or down. Significant cueing effects to targets presented to the left or right of the screen were found in these head orientation conditions. This suggests that attention was directed to the side to which the eyes would have been looking towards, had the face been presented upright. This finding provides evidence that head orientation can affect gaze following, even when the head orientation alone is not a social cue. It also shows that the mechanism responsible for the allocation of attention following a gaze cue can be influenced by intrinsic object-based (i.e. head-centred) properties of the task-irrelevant cue. |
Caren Bellmann; Mary P. Feely; Michael D. Crossland; Stamatina A. Kabanarou; Gary S. Rubin Fixation stability using central and pericentral fixation targets in patients with age-related macular degeneration Journal Article In: Ophthalmology, vol. 111, no. 12, pp. 2265–2270, 2004. @article{Bellmann2004, To determine fixation stability for central and pericentral fixation targets in patients with age-related macular degeneration (AMD). Comparative study. Twelve patients having late-stage AMD involving the fovea and 10 age-matched controls having no other eye diseases and visual acuity better than 20/25. Six different fixation targets (1°cross; 1°filled circle; 1°letter x; small 4-point diamond; large 4-point diamond using dimensions as in a field analyzer; large-crossover whole-image diagonal with open 1°center) were presented on a high-resolution monitor. Before examination, subjects were given verbal instructions to move their eye to see the center of the target best. Fixation stability was measured for the preferred eye, with the fellow eye occluded, using a gaze tracker. Fixation stability was quantified by calculating the bivariate contour ellipse area (BCEA) over 30 seconds for each target. For statistical analysis, BCEA values (minutes of arc2) were converted into their logarithms. The absolute retinal scotoma for the study eye was determined using a scanning laser ophthalmoscope. Bivariate contour ellipse area. Visual acuity in patients (age range, 57-87 years) ranged from 20/32 to 20/600. The lowest BCEA values were found for the 1°letter x in patients (mean, 12052.2%±254.0%) and for the 1°cross in normal subjects (mean, 1286.9%±47.8%); the highest BCEA values were found for the small 4-point diamond in patients (mean, 23109.5%±298.3%) and for the large 4-point diamond in normals (age range, 62-79 years) (mean, 3229.2%±105.4%). The difference between the targets was significant for normal subjects (analysis of variance [ANOVA], P<0.01) but not for patients (ANOVA, P>0.05). In normals, BCEA values were significantly lower for central fixation targets than for pericentral fixation targets (P<0.01). Fixation is significantly less stable for pericentral fixation targets in normal subjects, indicating an advantage for central fixation targets. These results are particularly significant for any clinical and experimental testing method that requires the patient to maintain stable fixation. |
Min Ju; Paul A. Luce Falling on sensitive ears. Constraints on bilingual lexical activation Journal Article In: Psychological Science, vol. 15, no. 5, pp. 314–318, 2004. @article{Ju2004, Spoken word recognition is characterized by multiple activation of sound patterns that are consistent with the acoustic-phonetic input. Recently, an extreme form of multiple activation was observed: Bilingual listeners activated words from both languages that were consistent with the input. We explored the degree to which bilingual multiple activation may be constrained by fine-grained acoustic-phonetic information. In a head-mounted eyetracking experiment, we presented Spanish-English bilinguals with spoken Spanish words having word-initial stop consonants with either English- or Spanish-appropriate voice onset times. Participants fixated interlingual distractors (nontarget pictures whose English names shared a phonological similarity with the Spanish targets) more frequently than control distractors when the target words contained English-appropriate voice onset times. These results demonstrate that fine-grained acoustic-phonetic information and a precise match between input and representation are critical for parallel activation of two languages. |
Marcus Kaiser; Markus Lappe Perisaccadic mislocalization orthogonal to saccade direction. Journal Article In: Neuron, vol. 41, pp. 293–300, 2004. @article{Kaiser2004, Saccadic eye movements transiently distort perceptual space. Visual objects flashed shortly before or during a saccade are mislocalized along the saccade direction, resembling a compression of space around the saccade target. These mislocalizations reflect transient errors of processes that construct spatial stability across eye movements. They may arise from errors of reference signals associated with saccade direction and amplitude or from visual or visuomotor remapping processes focused on the saccade target's position. The second case would predict apparent position shifts toward the target also in directions orthogonal to the saccade. We report that such orthogonal mislocalization indeed occurs. Surprisingly, however, the orthogonal mislocalization is restricted to only part of the visual field. This part comprises distant positions in saccade direction but does not depend on the target's position. Our findings can be explained by a combination of directional and positional reference signals that varies in time course across the visual field. |
Jukka Hyönä; Raymond Bertram; Alexander Pollstsek Are long compound words identified serially via their constituents? Evidence from an eye-movement contingent display change study Journal Article In: Memory & Cognition, vol. 32, no. 4, pp. 523–532, 2004. @article{Hyoenae2004a, The processing of two-constituent 12- to 18-letter Finnish compound nouns was studied by using an eye-movement–contingent display change technique. In the display change condition, all but the first 2 letters of the second constituent were replaced by visually similar letters until the eyes moved across an invisible boundary. When the eyes crossed the boundary, the second constituent was changed to its intended form. In the control condition, there was no display change. The frequency of the first con- stituent was also varied. The major findings were that (1) fixation time on the first constituent was strongly affected by the frequency of the first constituent but was not at all affected by whether the second constituent was visible, but (2) fixation time on the word subsequent to the first constituent's having been left was strongly affected by the display change. These results are most parsimoniously explained by the serial access of the two constituents for these long compound words. |
Dirk Kerzel Attentional load modulates mislocalization of moving stimuli, but does not eliminate the error Journal Article In: Psychonomic Bulletin & Review, vol. 11, no. 5, pp. 848–853, 2004. @article{Kerzel2004, Localization of the onset and offset of a moving target is subject to a number of errors that have to be attributed to events following or preceding the target event. Apparently, observers are unable to ignore the spatiotemporal context surrounding the target event. In two experiments, observers' attention was directed toward a single position along a trajectory, two positions along a single trajectory, or two positions along two different trajectories. In the latter condition, attention to details of a single trajectory was reduced. At the same time, motion type was manipulated by varying the temporal interval between successive target presentations. The localization error was not affected by attentional load; however, effects of motion type were eliminated when two trajectories had to be attended to. It may be sufficient to notice that the target has moved for localization errors to occur, while specifics of the trajectory are ignored. |
Reinhold Kliegl; Ellen Grabner; Martin Rolfs; Ralf Engbert Length, frequency, and predictability effects of words on eye movements in reading Journal Article In: European Journal of Cognitive Psychology, vol. 16, no. 1-2, pp. 262–284, 2004. @article{Kliegl2004, We tested the effects of word length, frequency, and predictability on inspection durations (first fixation, single fixation, gaze duration, and reading time) and inspection probabilities during first-pass reading (skipped, once, twice) for a corpus of 144 German sentences (1138 words) and a subset of 144 target words uncorrelated in length and frequency, read by 33 young and 32 older adults. For corpus words, length and frequency were reliably related to inspection durations and probabilities, predictability only to inspection probabilities. For first-pass reading of target words all three effects were reliable for inspection durations and probabilities. Low predictability was strongly related to second-pass reading. Older adults read slower than young adults and had a higher frequency of regressive movements. The data are to serve as a benchmark for computational models of eye movement control in reading. |
Jukka Hyönä; Robert F. Lorch Effects of topic headings on text processing: Evidence from adult readers' eye fixation patterns Journal Article In: Learning and Instruction, vol. 14, no. 2, pp. 131–152, 2004. @article{Hyoenae2004, Effects of topic headings on the processing of multiple-topic expository texts were examined with the help of readers' eye fixation patterns. Adult participants read two texts, one in which topic shifts were signaled by topic headings and one in which topic headings were excluded. The presence of topic headings facilitated the processing of topic sentences and increased the number of topics mentioned in the text summaries written after reading the texts. The facilitatory effect of headings was reflected both in the fixations made during the first-pass reading as well as in the later look-backs directed to the topic sentences. A framework is outlined to depict the process of reading and comprehending multiple-topic expository texts. |
Albrecht W. Inhoff; Cynthia M. Connine; Brianna M. Eiter; Ralph Radach; Dieter Heller Phonological representation of words in working memory during sentence reading Journal Article In: Psychonomic Bulletin & Review, vol. 11, no. 2, pp. 320–325, 2004. @article{Inhoff2004, The temporal dynamics of a visual target word's phonological representation was examined by presentation of an irrelevant spoken companion word when the participant's eyes reached the target's location during sentence reading. The spoken word was identical, similar, or dissimilar to the phonological specification of the visual target. All spoken words increased the time spent viewing the target, with larger effects in the similar and dissimilar spoken word conditions than in the identical condition. The reading of posttarget text was disrupted when the spoken word was similar but not when it was identical or dissimilar to the target. Phonological interference indicates that a word's phonological representation remains active after it has been identified during sentence reading. |
Gijs Plomp; Chie Nakatani; Valérìe Bonnardel; Cees Van Leeuwen Amodal completion as reflected by gaze durations Journal Article In: Perception, vol. 33, no. 10, pp. 1185–1200, 2004. @article{Plomp2004, In two experiments amodal completion of partly occluded shapes was investigated by recording eye movements in a directed visual-search task. Participants searched arrays of shapes in a prescribed order for target figures that could partly be occluded. Longer gaze durations were found on occlusion patterns than on truncated control patterns for targets but not for non- targets. This effect of occlusion was restricted to a subset of the stimuli. A second experiment was carried out to establish whether this restriction resulted from structural properties of the stimuli or their familiarity. Occlusion patterns in this experiment were ambiguous with respect to structure, allowing both local and global completions. One of the completions was always less familiar than the other. The results showed longer gazes only for the less familiar completions, irrespective of whether they were local or global. |
A. Panagopoulos; Michael W. Grünau; C. Galera Attentive mechanisms in visual search Journal Article In: Spatial Vision, vol. 17, no. 4-5, pp. 353–371, 2004. @article{Panagopoulos2004, Selective attention can be employed to a restricted region in space or to specific objects. Many properties of this attentional window or spotlight are not well understood. In the present study, we examined the question whether the putative shape of the attentional spotlight can be determined by endogenous cueing within a visual search paradigm. Participants searched for a target among distractors, which were arranged within a vertical or horizontal rectangle. The shape of this rectangle was cued endogenously in a valid or invalid way. Response times (RTs) to correct identification of target orientation were recorded. In Experiment 1, the difference between valid and invalid RTs demonstrated that cueing resulted in elongated attentional areas. This was true only for a group of experienced psychophysical participants, whereas a group of inexperienced participants were not able to use cueing in this way. In Experiment 2, the line motion illusion was used to examine the spatial properties of the attended area. The results confirmed for both experienced and inexperienced participants that attention was confined to the cued elongated area only. We present converging evidence for an attentional spotlight whose shape can be adjusted flexibly by appropriate endogenous cueing. |
Jason S. McCarley; Arthur F. Kramer; Christopher D. Wickens; Eric D. Vidoni; Walter R. Boot Visual skills in airport security inspection Journal Article In: Psychological Science, vol. 15, no. 5, pp. 302–306, 2004. @article{McCarley2004, An experiment examined visual performance in a simulated luggage-screening task. Observers participated in five sessions of a task requiring them to search for knives hidden in x-ray images of cluttered bags. Sensitivity and response times improved reliably as a result of practice. Eye movement data revealed that sensitivity increases were produced entirely by changes in observers' ability to recognize target objects, and not by changes in the effectiveness of visual scanning. Moreover, recognition skills were in part stimulus-specific, such that performance was degraded by the introduction of unfamiliar target objects. Implications for screener training are discussed. |
Eugene McSorley; Patrick Haggard; Robin Walker Distractor modulation of saccade trajectories: Spatial separation and symmetry affects Journal Article In: Experimental Brain Research, vol. 155, no. 3, pp. 320–333, 2004. @article{McSorley2004, The trajectories of saccadic eye movements can be modulated by the presence of a competing visual distractor. In the present study the trajectories of vertical saccades curved away from a single visual distractor presented in one visual field, but tended to be straight when two distractors were presented at mirror symmetric locations in both visual fields. The spatial nature of the mirror distractor effect was examined by presenting a second distractor at mirror and non-mirror locations. Saccade trajectories also tended to be straight with both mirror and non-mirror symmetrical distractors. The relationship between the distractor location and saccade curvature was examined in a third experiment by manipulating the distractor-to-target spatial separation. Although there was a tendency for greater curvature when the distractor was presented in the same hemifield as the target there was no clear relationship between curvature and distractor location. The results show that the distractor modulation of saccade trajectory is not highly spatially specific and that it can be balanced by a second bilateral distractor in the opposite visual field. The results are interpreted in terms of a model in which the initial saccade direction and curvature back towards the saccade goal are controlled by separate processes. Initial saccade direction is modulated by the inhibition of distractor locations within a 'motor map' specifying saccade direction. Curvature back towards the saccade goal may be attributed to a feedback system, with a separate representation of the visual target location, that enables an on-line correction of the saccade during mid-flight. |
Matthew S. Peterson; Walter Boot; Arthur F. Kramer; Jason S. McCarley Landmarks help guide attention during visual search Journal Article In: Spatial Vision, vol. 17, no. 4-5, pp. 497–510, 2004. @article{Peterson2004, Using a novel visual search paradigm McCarley et al. (2003) concluded that the oculomotor system keeps a history of 3-4 previously attended objects. However, their displays were visually sparse, denying participants structural information which might be used during normal search. This might have underestimated memory capacity. To examine this possibility, we included landmarks in the same search paradigm. Previously examined items were re-examined less frequently when landmarks were present compared to when they were absent. Results indicate that objects in the environment that share no features with search items are used as external support to aid memory in guiding visual search. |
Matthew S. Peterson; Arthur F. Kramer; David E. Irwin Covert shifts of attention precede involuntary eye movements Journal Article In: Perception and Psychophysics, vol. 66, no. 3, pp. 398–405, 2004. @article{Peterson2004a, There is considerable evidence that covert visual attention precedes voluntary eye movements to an intended location. What happens to covert attention when an involuntary saccadic eye movement is made? In agreement with other researchers, we found that attention and voluntary eye movements are tightly coupled in such a way that attention always shifts to the intended location before the eyes begin to move. However, we found that when an involuntary eye movement is made, attention first precedes the eyes to the unintended location and then switches to the intended location, with the eyes following this pattern a short time later. These results support the notion that attention and saccade programming are tightly coupled. |
Tobias Pflugshaupt; Stefanie Almoslöchner Bopp; Dörthe Heinemann; Urs P. Mosimann; Roman Von Wartburg; Thomas Nyffeler; Christian W. Hess; René M. Müri Residual oculomotor and exploratory deficits in patients with recovered hemineglect Journal Article In: Neuropsychologia, vol. 42, no. 9, pp. 1203–1211, 2004. @article{Pflugshaupt2004, Several studies on hemineglect have reported that patients recover remarkably well when assessed with neuropsychological screening tests, however, they show deficits on novel or complex tasks. We investigated whether such deficits can be revealed with eye movement analysis, applying two basic oculomotor tasks as well as two exploratory tasks. Eye movements were recorded in eight hemineglect patients at least eleven months after right-hemisphere brain damage had occurred. Sixteen healthy volunteers participated in the control group. Regarding the basic oculomotor tasks, only the overlap task revealed residual deficits in patients, suggesting that a directional deficit in disengaging attention persisted during recovery. Further residual deficits were evident in the exploratory tasks. When everyday scenes were explored, patients showed a bias in early orienting towards the ipsilateral hemispace. In a search task, they demonstrated the same orienting bias as well as a non-directional deficit concerning search times. Moreover, patients preferentially fixated in the contralateral hemispace, but did not benefit from this asymmetry in terms of search times, i.e. they did not detect contralateral targets faster than ipsilateral ones. This suggests a dissociation between oculomotor processes and attentional ones. In conclusion, we have identified behavioural aspects that seem to recover slower than others. A disengagement deficit and biases in early orienting have been the most pronounced residual oculomotor deficits. |
Fumiko Maeda; Ryota Kanai; Shinsuke Shimojo Changing pitch induced visual motion illusion Journal Article In: Current Biology, vol. 14, no. 23, pp. 1–2, 2004. @article{Maeda2004, We often associate moving objects and changing pitch, e.g., falling stones with descending, and launching rockets with ascending pitch, even when these sounds do not happen in the real- world. The reason for this is unknown. Here we report an illusion in which auditory stimuli with no apparent spatial and motion information [1–3] alter human visual motion perception. |
Paresh Malhotra; Sabira K. Mannan; Jon Driver; Masud Husain Special section impaired spatial working memory: One component of the visual neglect syndrome ? Journal Article In: Cortex, vol. 40, no. 4-5, pp. 667–676, 2004. @article{Malhotra2004, Both impaired spatial working memory (SWM) and unilateral neglect may follow damage to the right parietal lobe. We propose that impaired SWM can exacerbate visual neglect, due to failures in remembering locations that have already been searched. When combined with an attentional bias to the ipsilesional right side, such a SWM impairment should induce recursive search of ipsilesional locations. Here we studied a left neglect patient with a right temporoparietal haemorrhage. On a nonlateralised, purely vertical SWM task, he was impaired in retaining spatial locations. In a visual search task, his eye position was monitored while his spatial memory was probed. He recursively searched through right stimuli, re-fixating previously inspected items, and critically treated them as if they were new discoveries, consistent with the SWM deficit. When his recovery was tracked over several months, his SWM deficit and left neglect showed concurrent improvements. We argue that impaired SWM may be one important component of the visual neglect syndrome. |
2003 |
James S. Magnuson; Michael K. Tanenhaus; Richard N. Aslin; Delphine Dahan The microstructure of spoken word recognition: Studies with artificial lexicons Journal Article In: Journal of Experimental Psychology: General, vol. 132, no. 2, pp. 202–227, 2003. @article{Magnuson2003a, The time course of spoken word recognition depends largely on the frequencies of a word and its competitors, or neighbors (similar-sounding words). However, variability in natural lexicons makes systematic analysis of frequency and neighbor similarity difficult. Artificial lexicons were used to achieve precise control over word frequency and phonological similarity. Eye tracking provided time course measures of lexical activation and competition (during spoken instructions to perform visually guided tasks) both during and after word learning, as a function of word frequency, neighbor type, and neighbor frequency. Apparent shifts from holistic to incremental competitor effects were observed in adults and neural network simulations, suggesting such shifts reflect general properties of learning rather than changes in the nature of lexical representations. |
James S. Magnuson; Michael K. Tanenhaus; Richard N. Aslin; Delphine Dahan The time course of spoken word learning and recognition: Studies with artificial lexicons Journal Article In: Journal of Experimental Psychology: General, vol. 132, no. 2, pp. 202–227, 2003. @article{Magnuson2003, The time course of spoken word recognition depends largely on the frequencies of a word and its competitors, or neighbors (similar-sounding words). However, variability in natural lexicons makes systematic analysis of frequency and neighbor similarity difficult. Artificial lexicons were used to achieve precise control over word frequency and phonological similarity. Eye tracking provided time course measures of lexical activation and competition (during spoken instructions to perform visually guided tasks) both during and after word learning, as a function of word frequency, neighbor type, and neighbor frequency. Apparent shifts from holistic to incremental competitor effects were observed in adults and neural network simulations, suggesting such shifts reflect general properties of learning rather than changes in the nature of lexical representations. |
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. |
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. |
Ervin Poljac; Albert V. Berg Representation of heading direction in far and near head space Journal Article In: Experimental Brain Research, vol. 151, no. 2, pp. 501–513, 2003. @article{Poljac2003, Manipulation of objects around the head requires an accurate and stable internal representation of their locations in space, also during movements such as that of the eye or head. For far space, the representation of visual stimuli for goal-directed arm movements relies on retinal updating, if eye movements are involved. Recent neurophysiological studies led us to infer that a transformation of visual space from retinocentric to a head-centric representation may be involved for visual objects in close proximity to the head. The first aim of this study was to investigate if there is indeed such a representation for remembered visual targets of goal-directed arm movements. Participants had to point toward an initially foveated central target after an intervening saccade. Participants made errors that reflect a bias in the visuomotor transformation that depends on eye displacement rather than any head-centred variable. The second issue addressed was if pointing toward the centre of a wide-field expanding motion pattern involves a retinal updating mechanism or a transformation to a head-centric map and if that process is distance dependent. The same pattern of pointing errors in relation to gaze displacement was found independent of depth. We conclude that for goal-directed arm movements, representation of the remembered visual targets is updated in a retinal frame, a mechanism that is actively used regardless of target distance, stimulus characteristics or the requirements of the task. |
Marc Pomplun; Eyal M. Reingold; Jiye Shen Area activation: A computational model of saccadic selectivity in visual search Journal Article In: Cognitive Science, vol. 27, no. 2, pp. 299–312, 2003. @article{Pomplun2003, The Area Activation Model (Pomplun, Reingold, Shen, & Williams, 2000) is a computational model predicting the statistical distribution of saccadic endpoints in visual search tasks. Its basic assumption is that saccades in visual search tend to foveate display areas that provide a maximum amount of task-relevant information for processing during the subsequent fixation. In the present study, a counterintuitive prediction by the model is empirically tested, namely that saccadic selectivity towards stimulus features depends on the spatial arrangement of search items. We find good correspondence between simulated and empirically observed selectivity patterns, providing strong support for the Area Activation Model. |
James A. Mazer; Jack L. Gallant Goal-related activity in V4 during free viewing visual search: Evidence for a ventral stream visual salience map Journal Article In: Neuron, vol. 40, no. 6, pp. 1241–1250, 2003. @article{Mazer2003, Natural exploration of complex visual scenes depends on saccadic eye movements toward important locations. Saccade targeting is thought to be mediated by a retinotopic map that represents the locations of salient features. In this report, we demonstrate that extrastriate ventral area V4 contains a retinotopic salience map that guides exploratory eye movements during a naturalistic free viewing visual search task. In more than half of recorded cells, visually driven activity is enhanced prior to saccades that move the fovea toward the location previously occupied by a neuron's spatial receptive field. This correlation suggests that bottom-up processing in V4 influences the oculomotor planning process. Half of the neurons also exhibit top-down modulation of visual responses that depends on search target identity but not visual stimulation. Convergence of bottom-up and top-down processing streams in area V4 results in an adaptive, dynamic map of salience that guides oculomotor planning during natural vision. |
Jason S. McCarley; Arthur F. Kramer; Gregory J. DiGirolamo Differential effects of the Müller-Lyer illusion on reflexive and voluntary saccades Journal Article In: Journal of Vision, vol. 3, no. 11, pp. 751–760, 2003. @article{McCarley2003, Research has produced conflicting evidence as to whether saccade programming is or is not biased by perceptual illusions. However, previous studies have generally not distinguished between effects of illusory percepts on reflexive saccades, programmed automatically in response to an external visual signal, and voluntary saccades, programmed purposively to a location where no signal has occurred. Here we find that voluntary and reflexive saccades are differentially susceptible to the Müller-Lyer illusion; reflexive movements are reliably but modestly affected by the illusion, whereas voluntary movements show an effect similar to that of perceptual judgments. Results suggest that voluntary saccade programming occurs within a non-retinotopic spatial representation similar to that of visual consciousness, whereas reflexive saccade programming occurs within a representation integrating retinotopic and higher level spatial frames. The effects of the illusion on reflexive saccades are not subject to endogenous control, nor are they modulated by the strength of an exogenous target signal. |
Jason S. Mccarley; Ranxiao F. Wang; Arthur F. Kramer; David E. Irwin; Matthew S. Peterson How much memory does oculomotor search have? Journal Article In: Psychological Science, vol. 14, no. 5, pp. 422–426, 2003. @article{Mccarley2003b, Research has demonstrated that oculomotor visual search is guided by memory for which items or locations within a display have already been inspected. In the study reported here, we used a gaze-contingent search paradigm to examine properties of this memory. Data revealed a memory buffer for search history of three to four items. This buffer was effected in part by a space-based trace attached to a location independently of whether the object that had been seen at that position remained visible, and was subject to interference from other stimuli seen in the course of a trial. |
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. |
David Crundall; Peter Chapman; Nicola Phelps; Geoffrey Underwood Eye movements and hazard perception in police pursuit and emergency response driving Journal Article In: Journal of Experimental Psychology: Applied, vol. 9, no. 3, pp. 163–174, 2003. @article{Crundall2003, How do police cope with the visual demands placed on them during pursuit driving? This study compared the hazard ratings, eye movements, and physiological responses of police drivers with novice and with age-matched control drivers while viewing video clips of driving taken from police vehicles. The clips included pursuits, emergency responses, and control drives. Although police drivers did not report more hazards than the other participants reported, they had an increased frequency of electrodermal responses while viewing dangerous clips and a greater visual sampling rate and spread of search. However, despite an overall police advantage in oculomotor and physiological measures, all drivers had a reduced spread of search in nighttime pursuits because of the focusing of overt attention. |
Michael Coesmans; Peter A. Sillevis Smitt; David J. Linden; Ryuichi Shigemoto; Tomoo Hirano; Yoshinori Yamakawa; Adriaan M. Alphen; Chongde Luo; Josef N. Geest; Johan M. Kros; Carlos A. Gaillard; Maarten A. Frens; Chris I. De Zeeuw Mechanisms underlying cerebellar motor deficits due to mGluR1-autoantibodies Journal Article In: Annals of Neurology, vol. 53, no. 3, pp. 325–336, 2003. @article{Coesmans2003, Patients with Hodgkin's disease can develop paraneoplastic cerebellar ataxia because of the generation of autoantibodies against mGluR1 (mGluR1-Abs). Yet, the pathophysiological mechanisms underlying their motor coordination deficits remain to be elucidated. Here, we show that application of IgG purified from the patients' serum to cerebellar slices of mice acutely reduces the basal activity of Purkinje cells, whereas application to the flocculus of mice in vivo evokes acute disturbances in the performance of their compensatory eye movements. In addition, the mGluR1-Abs block induction of long-term depression in cultured mouse Purkinje cells, whereas the cerebellar motor learning behavior of the patients is affected in that they show impaired adaptation of their saccadic eye movements. Finally, postmortem analysis of the cerebellum of a paraneoplastic cerebellar ataxia patient showed that the number of Purkinje cells was significantly reduced by approximately two thirds compared with three controls. We conclude that autoantibodies against mGluR1 can cause cerebellar motor coordination deficits caused by a combination of rapid effects on both acute and plastic responses of Purkinje cells and chronic degenerative effects. |
Angela M. Colcombe; Arthur F. Kramer; David E. Irwin; Matthew S. Peterson; Stanley Colcombe; Sowon Hahn Age-related effects of attentional and oculomotor capture by onsets and color singletons as a function of experience Journal Article In: Acta Psychologica, vol. 113, no. 2, pp. 205–225, 2003. @article{Colcombe2003, The present experiment examined the degree to which experience with different stimulus characteristics affects attentional capture, particularly as related to aging. Participants were presented with onset target/color singleton distractor or color singleton target/onset distractor pairs across three experimental sessions. The target/distractor pairs were reversed in the second session such that the target in the first session became the distractor in the second and third sessions. For both young and old adults previous experience with color as a target defining feature influenced oculomotor capture with task-irrelevant color distractors. Experience with sudden onsets had the same effect for younger and older adults, although capture effects were substantially larger for onset than for color distractors. Experience-based capture effects diminished relatively rapidly after target and distractor-defining properties were reversed. The results are discussed in terms of top-down and stimulus-driven effects on age-related differences in attentional control. ©2003 Elsevier Science B.V. All rights reserved. |
Leonardo Chelazzi; Elisabeth Moores; Liana Laiti Associative knowledge controls deployment of visual selective attention Journal Article In: Nature neuroscience, vol. 6, no. 2, pp. 182–189, 2003. @article{Chelazzi2003, According to some models of visual selective attention, objects in a scene activate corresponding neural representations, which compete for perceptual awareness and motor behavior. During a visual search for a target object, top-down control exerted by working memory representations of the target's defining properties resolves competition in favor of the target. These models, however, ignore the existence of associative links among object representations. Here we show that such associations can strongly influence deployment of attention in humans. In the context of visual search, objects associated with the target were both recalled more often and recognized more accurately than unrelated distractors. Notably, both target and associated objects competitively weakened recognition of unrelated distractors and slowed responses to a luminance probe. Moreover, in a speeded search protocol, associated objects rendered search both slower and less accurate. Finally, the first saccades after onset of the stimulus array were more often directed toward associated than control items. |
Mike Rinck; Elena Gámez; José M. Díaz; Manuel De Vega Processing of temporal information: Evidence from eye movements Journal Article In: Memory & Cognition, vol. 31, no. 1, pp. 77–86, 2003. @article{Rinck2003, In two experiments, we recorded eye movements to study how readers monitor temporal order information contained in narrative texts. Participants read short texts containing critical temporal information in the sixth sentence, which could be either consistent or inconsistent with temporal order information given in the second sentence. In Experiment 1, inconsistent sentences yielded more regressions to the second sentence and longer refixations of it. In Experiment 2, this pattern of eye movements was shown only by readers who noticed the inconsistency and were able to report it. Theoretical and methodological implications of the results for research on text comprehension are discussed. |
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. |
Andreas Schiegg; Heiner Deubel; Werner X. Schneider Attentional selection during preparation of prehension movements Journal Article In: Visual Cognition, vol. 10, no. 4, pp. 409–431, 2003. @article{Schiegg2003, In two experiments coupling between dorsal attentional selection for action and ventral attentional selection for perception during preparation of prehension movements was examined. In a dual-task paradigm subjects had to grasp an "X"-shaped object with either the left or the right hand's thumb and index finger. Simultaneously a discrimination task was used to measure visual attention prior to the execution of the prehension movements: Mask items transiently changed into distractors or discrimination targets. There was exactly one discrimination target per trial, which appeared at one of the four branch ends of the object. In Experiment 1 target position varied randomly while in Experiment 2 it was constant and known to subjects in each block of trials. In both experiments discrimination performance was significantly better for discrimination target positions at to-be-grasped branch ends than for not-to-be-grasped branch ends. We conclude that during preparation of prehension movements visual attention is largely confined to those parts of an object that will be grasped. |
Yutaka Sakaguchi Visual field anisotropy revealed by perceptual filling-in Journal Article In: Vision Research, vol. 43, no. 19, pp. 2029–2038, 2003. @article{Sakaguchi2003, Four experiments were performed to investigate how the time required for perceptual filling-in varies with the position of the target in the visual field. Conventional studies have revealed that filling-in is facilitated by a target with greater eccentricity, while no systematic studies have examined the effect of polar angle. Experiment 1 examined the effect of polar angle when the target and surround differed in luminance. Filling-in was facilitated as the target position changed from the horizontal to the vertical meridian. This dependency was more prominent in the upper field than in the lower, although no asymmetry was found between the left and right visual fields. These features were observed in both monocular and binocular viewing. These results were replicated in a modified stimulus configuration, in which the surround was a circular region concentric with the target (Experiment 2). Moreover, it was confirmed that the asymmetry was not due to fluctuation in the retinal image (i.e., eye movement) (Experiment 3). Finally, Experiment 4 examined whether this anisotropy was observed when two differently oriented gratings were presented in the target and surround regions. Again, filling-in was facilitated for a target close to the vertical meridian, irrespective of the relationship between the target and surround orientations. The underlying mechanism of this anisotropy is discussed from the viewpoints of cortical magnification and neural connections in the visual cortex. |
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. |
N. J. Upton; Timothy L. Hodgson; G. T. Plant; Richard J. S. Wise; Alexander P. Leff "Bottom-up" and "top-down" effects on reading saccades: A case study Journal Article In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 74, no. 10, pp. 1423–1428, 2003. @article{Upton2003, OBJECTIVE: To investigate the role right foveal/parafoveal sparing plays in reading single words, word arrays, and eye movement patterns in a single case with an incongruous hemianopia. METHODS: The patient, a 48-year-old right handed male with a macular sparing hemianopia in his left eye and a macular splitting hemianopia in his right eye, performed various reading tasks. Single word reading speeds were monitored using a "voice-trigger" system. Eye movements were recorded while reading three passages of text, and PET data were gathered while the subject performed a variety of reading tasks in the camera. RESULTS: The patient was faster at reading single words and text with his left eye compared with his right. A small word length effect was present in his right eye but not his left. His eye movement patterns were more orderly when reading text with his left eye, making fewer saccades. The PET data provided evidence of "top-down" processes involved in reading. Binocular single word reading produced activity in the representation of foveal V1 bilaterally; however, text reading with the left eye only was associated with activation in left but not right parafoveal V1, despite there being visual stimuli in both visual fields. CONCLUSIONS: The presence of a word length effect (typically associated with pure alexia) can be caused by a macular splitting hemianopia. Right parafoveal vision is not critically involved in single word identification, but is when planning left to right reading saccades. The influence of top-down attentional processes during text reading can be visualised in parafoveal V1 using PET. |
Seppo Vainio; Jukka Hyönä; Anneli Pajunen Facilitatory and inhibitory effects of grammatical agreement: Evidence from readers' eye fixation patterns Journal Article In: Brain and Language, vol. 85, no. 2, pp. 197–202, 2003. @article{Vainio2003, The study examined how grammatical agreement affects reading in Finnish. Readers' eye fixation patterns were recorded when they read one of three alternative versions of the same sentences, where the critical difference was the type of preceding word of the target nouns. The preceding word was (a) an agreeing modifier (mainioksi orkesteriksi='for an excellent orchestra'), (b) a non-agreeing modifier that was grammatical, unambiguous and synonymous to the agreeing modifier (kelpo orkesteriksi='for an excellent orchestra'), or (c) a baseline condition without a modifier (orkesteriksi='for an orchestra'). Two different types of agreement were used, a modifier-head agreement and a possessive agreement. The results showed that the agreeing modifiers facilitate and the non-agreeing modifiers inhibit the reading of the target nouns compared to the neutral baseline condition. These effects appeared in the second-pass reading. The pattern was similar between the two agreement structures. |
Dimitris Agrafiotis; Nishan Canagarajah; David R. Bull; Matthew Dye Perceptually optimised sign language video coding based on eye tracking analysis Journal Article In: Electronics Letters, vol. 39, pp. 1–2, 2003. @article{Agrafiotis2003, A perceptually optimised approach to sign language video coding is presented. The proposed approach is based on the results (included) of an eye tracking study in the visual attention of sign language viewers. Results show reductions in bit rate of over 30% with very good subjective quality. |
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 |
Dominic J. Mort; Richard J. Perry; Sabira K. Mannan; Timothy L. Hodgson; Elaine Anderson; Rebecca Quest; Donald McRobbie; Alan McBride; Masud Husain; Christopher Kennard Differential cortical activation during voluntary and reflexive saccades in man Journal Article In: NeuroImage, vol. 18, no. 2, pp. 231–246, 2003. @article{Mort2003, A saccade involves both a step in eye position and an obligatory shift in spatial attention. The traditional division of saccades into two types, the "reflexive" saccade made in response to an exogenous stimulus change in the visual periphery and the "voluntary" saccade based on an endogenous judgement to move gaze, is supported by lines of evidence which include the longer onset latency of the latter and the differential effects of lesions in humans and primates on each. It has been supposed that differences between the two types of saccade derive from differences in how the spatial attention shifts involved in each are processed. However, while functional imaging studies have affirmed the close link between saccades and attentional shifts by showing they activate overlapping cortical networks, attempts to contrast exogenous with endogenous ("covert") attentional shifts directly have not revealed separate patterns of cortical activation. We took the "overt" approach, contrasting whole reflexive and voluntary saccades using event-related fMRI. This demonstrated that, relative to reflexive saccades, voluntary saccades produced greater activation within the frontal eye fields and the saccade-related area of the intraparietal sulci. The reverse contrast showed reflexive saccades to be associated with relative activation of the angular gyrus of the inferior parietal lobule, strongest in the right hemisphere. The frequent involvement of the right inferior parietal lobule in lesions causing hemispatial neglect has long implicated this parietal region in an important, though as yet uncertain, role in the awareness and exploration of space. This is the first study to demonstrate preferential activation of an area in its posterior part, the right angular gyrus, during production of exogenously triggered rather than endogenously generated saccades, a finding which we propose is consistent with an important role for the angular gyrus in exogenous saccadic orienting. |
Karen Mortier; Mieke Donk; Jan Theeuwes Attentional capture within and between objects Journal Article In: Acta Psychologica, vol. 113, pp. 133–145, 2003. @article{Mortier2003, The present study addressed the question whether attentional capture by abrupt onsets is affected by object-like properties of the stimulus field. Observers searched for a target circle at one of four ends of two solid rectangles. In the focused attention condition the location of the upcoming target was cued by means of a central arrowhead, whereas in the divided attention condition, the target location was not cued. Irrelevant abrupt onsets could appear either within the attended or within the non-attended object. The results showed that in the focused attention condition, onsets ceased to capture attention irrespective of whether the onset appeared within an attended object or within a non-attended object. © 2003 Elsevier Science B.V. All rights reserved. |
Helena Ojanpää; Risto Näsänen Effects of luminance and colour contrast on the search of information on display devices Journal Article In: Displays, vol. 24, no. 4-5, pp. 167–178, 2003. @article{Ojanpaeae2003, For black-and-white alphanumeric information, the speed of visual perception decreases with decreasing contrast. We investigated the effect of luminance contrast on the speed of visual search and reading when characters and background differed also with respect to colour. The luminance contrast between background and characters was varied, while colour contrast was held nearly constant. Stimuli with moderate (green/grey) or high colour contrast (green/red or yellow/blue), and three character sizes (0.17, 0.37, and 1.26deg) were used. Eye movements were recorded during the visual search task. We found that the visual search times, number of eye fixations, and mean fixation durations increased strongly with decreasing luminance contrast despite the presence of colour contrast. The effects were largest for small characters (0.17deg), but occurred also for medium (0.37deg), and in some cases for large (1.26deg) characters. Similarly, reading rates decreased with decreasing luminance contrast. Thus, moderate or even high colour contrast does not guarantee quick visual perception, if the luminance contrast between characters and background is small. This is probably due to the fact that visual acuity (the ability to see small details) is considerably lower for pure colour information than for luminance information. Therefore, in user interfaces, good visibility of alphanumeric information requires clear luminance (brightness) difference between foreground and background. |
Helena Ojanpää; Risto Näsänen Utilisation of spatial frequency information in face search Journal Article In: Vision Research, vol. 43, no. 24, pp. 2505–2515, 2003. @article{Ojanpaeae2003a, In previous studies the utilisation of spatial frequency information in face perception has been investigated by using static recognition tasks. In this study we used a visual search task, which requires eye movements and fast identification of previously learned facial photographs. Using Fourier phase randomisation, spatial information was selectively removed without changing the amplitude spectrum of the image. Fourier phase was randomised within one-octave wide bands of nine different centre spatial frequencies (2-32 c/face width, 0.63-10.1 c/deg). In a control condition no randomisation was used. All stimuli had similar contrast. Search times and eye movements during the search were measured. The removal of spatial information by phase randomisation at medium spatial frequencies resulted in a considerable increase of search times. In the main experiment the maximum of the search times occurred between 8 and 11 c/ face width. The number of eye fixations behaved similarly. In an additional experiment with a threefold viewing distance the search times increased and the maximum of the search times shifted slightly to lower object spatial frequencies (5.6-8 c/face width). This suggests that the band of spatial frequencies used in face search is not completely scale invariant. The results show that information most important to face search is located at a limited band of mid spatial frequencies. This is consistent with earlier studies, in which non-dynamical face recognition tasks and low-contrast stimuli have been used. |
Risto Näsänen; Helena Ojanpää Effect of image contrast and sharpness on visual search for computer icons Journal Article In: Displays, vol. 24, pp. 137–144, 2003. @article{Naesaenen2003, The purpose of the study was to determine the effect of image blur and contrast on the speed of visual search for user interface icons and investigate how the effect is reflected in eye movement parameters. The task of the observer was to search for a target icon from among a rectangular array of distracter icons. A staircase algorithm was used to determine the stimulus presentation time, threshold search time, for which the probability of correct responses was 0.79. Simultaneously, eye-movements were recorded with a video eye-tracker with a sampling rate of 250 Hz. Image sharpness was varied by filtering the stimulus images with a Gaussian low-pass filter. The results showed that with increasing contrast or sharpness search time, number of fixations per search, and fixation duration first decreased, and then became constant at medium levels of contrast or sharpness. These effects were somewhat more pronounced for contrast than for sharpness. Saccade amplitudes were not affected by contrast or sharpness. The results suggest that the perception of user interface icons is quite resistant to small or moderate deterioration of image quality. |
Antje S. Meyer; Ardi Roelofs; Willem J. M. Levelt Word length effects in object naming: The role of a response criterion Journal Article In: Journal of Memory and Language, vol. 48, pp. 131–147, 2003. @article{Meyer2003, According to Levelt, Roelofs, and Meyer (1999) speakers generate the phonological and phonetic representations of successive syllables of a word in sequence and only begin to speak after having fully planned at least one complete phonological word. Therefore, speech onset latencies should be longer for long than for short words. We tested this prediction in four experiments in which Dutch participants named or categorized objects with monosyllabic or di- syllabic names. Experiment 1 yielded a length effect on production latencies when objects with long and short names were tested in separate blocks, but not when they were mixed. Experiment 2 showed that the length effect was not due to a difference in the ease of object recognition. Experiment 3 replicated the results of Experiment 1 using a within-participants design. In Experiment 4, the long and short target words appeared in a phrasal context. In addition to the speech onset latencies, we obtained the viewing times for the target objects, which have been shown to depend on the time necessary to plan the form of the target names. We found word length effects for both dependent variables, but only when objects with short and long names were presented in separate blocks. We argue that in pure and mixed blocks speakers used different response deadlines, which they tried to meet by either generating the motor programs for one syllable or for all syllables of the word before speech onset. Computer simulations using WEAVER++ support this view. |
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 develop- ment 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 evolu- tion, and one that enabled not just managed foraging, but perhaps modern culture itself. |
Johannes M. Zanker; Melanie Doyle; Robin Walker Gaze stability of observers watching Op Art pictures Journal Article In: Perception, vol. 32, no. 9, pp. 1037–1049, 2003. @article{Zanker2003, It has been the matter of some debate why we can experience vivid dynamic illusions when looking at static pictures composed from simple black and white patterns. The impression of illusory motion is particularly strong when viewing some of the works of 'Op Artists, such as Bridget Riley's painting Fall. Explanations of the illusory motion have ranged from retinal to cortical mechanisms, and an important role has been attributed to eye movements. To assess the possible contribution of eye movements to the illusory-motion percept we studied the strength of the illusion under different viewing conditions, and analysed the gaze stability of observers viewing the Riley painting and control patterns that do not produce the illusion. Whereas the illusion was reduced, but not abolished, when watching the painting through a pinhole, which reduces the effects of accommodation, it was not perceived in flash afterimages, suggesting an important role for eye movements in generating the illusion for this image. Recordings of eye movements revealed an abundance of small involuntary saccades when looking at the Riley pattern, despite the fact that gaze was kept within the dedicated fixation region. The frequency and particular characteristics of these rapid eye movements can vary considerably between different observers, but, although there was a tendency for gaze stability to deteriorate while viewing a Riley painting, there was no significant difference in saccade frequency between the stimulus and control patterns. Theoretical considerations indicate that such small image displacements can generate patterns of motion signals in a motion-detector network, which may serve as a simple and sufficient, but not necessarily exclusive, explanation for the illusion. Why such image displacements lead to perceptual results with a group of Op Art and similar patterns, but remain invisible for other stimuli, is discussed. |
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. |
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. |
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. |
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. |
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. |
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. |
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. |
Adele Diederich; Hans Colonius; Daniela Bockhorst; Sandra Tabeling Visual-tactile spatial interaction in saccade generation Journal Article In: Experimental Brain Research, vol. 148, no. 3, pp. 328–337, 2003. @article{Diederich2003, Saccadic reaction times to visual targets tend to be faster when non-visual stimuli are presented in close temporal or spatial proximity even if subjects are instructed to ignore the accessory input. The effect tends to decrease with increasing spatial distance between the stimuli. Multisensory interaction effects measured in neural structures involved in saccade generation have demonstrated a similar spatial dependence. The present study investigated visual-tactile interaction effects on saccadic reaction time using a focused attention paradigm. Compared to unimodal visual targets saccadic reaction time to bimodal stimuli was reduced by up to 30 ms. The effect was larger for ipsi- than for contralateral presentations, and it increased with the eccentricity of the visual target. The results are consistent with attributing part of the facilitation to a multisensory effect of bimodal neurons with overlapping visual and tactile receptive field structures in the deep layers of the superior colliculus. |
Hendrik Chris Dijkerman; Robert D. McIntosh; David Milner; Yves Rossetti; Caroline Tilikete; Richard C. Roberts Ocular scanning and perceptual size distortion in hemispatial neglect: Effects of prism adaptation and sequential stimulus presentation Journal Article In: Experimental Brain Research, vol. 153, no. 2, pp. 220–230, 2003. @article{Dijkerman2003, When asked to compare two lateralized shapes for horizontal size, neglect patients often indicate the left stimulus to be smaller. Gainotti and Tiacci (1971) hypothesized that this phenomenon might be related to a rightward bias in the patients' gaze. This study aimed to assess the relation between this size underestimation and oculomotor asymmetries. Eye movements were recorded while three neglect patients judged the horizontal extent of two rectangles. Two experimental manipulations were performed to increase the likelihood of symmetrical scanning of the stimulus display. The first manipulation entailed a sequential, rather than simultaneous presentation of the two rectangles. The second required adaptation to rightward displacing prisms, which is known to reduce many manifestations of neglect. All patients consistently underestimated the left rectangle, but the pattern of verbal responses and eye movements suggested different underlying causes. These include a distortion of space perception without ocular asymmetry, a failure to view the full leftward extent of the left stimulus, and a high-level response bias. Sequential presentation of the rectangles and prism adaptation reduced ocular asymmetries without affecting size underestimation. Overall, the results suggest that leftward size underestimation in neglect can arise for a number of different reasons. Incomplete leftward scanning may perhaps be sufficient to induce perceptual size distortion, but it is not a necessary prerequisite. |
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. |
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{Shimojo2003, 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. |
Scott D. Slotnick; Jens Schwarzbach; Steven Yantis Attentional inhibition of visual processing in human striate and extrastriate cortex Journal Article In: NeuroImage, vol. 19, no. 4, pp. 1602–1611, 2003. @article{Slotnick2003, Allocating attention to a spatial location in the visual field is associated with an increase in the cortical response evoked by a stimulus at that location, compared to when the same stimulus is unattended. We used event-related functional magnetic resonance imaging to investigate attentional modulation of the cortical response to a stimulus probe at an attended location and to multiple probes at unattended locations. A localizer task and retinotopic mapping were used to precisely identify the cortical representations of each probe within striate (V1) and extrastriate cortex (V2, VP, V3, V4v, and V3A). The magnitude and polarity of attentional modulation were assessed through analysis of event-related activity time-locked to shifts in spatial attention. Attentional facilitation at the attended location was observed in striate and extrastriate cortex, corroborating earlier findings. Attentional inhibition of visual stimuli near the attended location was observed in striate cortex, and attentional inhibition of more distant stimuli occurred in both striate and extrastriate cortex. These findings indicate that visual attention operates both through facilitation of visual processing at the attended location and through inhibition of unattended stimulus representations in striate and extrastriate cortex. |
Jeroen B. J. Smeets; Ignace T. C. Hooge Nature of variability in saccades Journal Article In: Journal of Neurophysiology, vol. 90, no. 1, pp. 12–20, 2003. @article{Smeets2003, We studied the variability in saccades by comparing the peak velocities of saccades with the same target amplitude made with different actual amplitudes. We tested three hypotheses: the pulse-height noise hypothesis (peak velocity and amplitude vary proportionally), the localization noise hypothesis (variability in amplitude and peak velocity lie along the main sequence), and the independent noise hypothesis (variability in amplitude and peak velocity are independent). We measured eye orientation in two experiments by a scleral coil and a video system. Surprisingly, the main source of variability of saccades depended on the measurement system used. A combination of localization noise and independent noise best describes the data obtained by the video system. The independent noise (e.g., measurement inaccuracy) was the main source of variability. For the scleral coils, the variability was considerably larger than for the less accurate video system. The pulse-height noise hypothesis best describes this additional variability. Therefore we conclude that pulse-height noise is the main source of variability in saccades measured with scleral coils. We discuss the influence of scleral coils on saccade generation and suggest that a change in motor strategy due to the discomfort of wearing the coils might be the cause of the increased variability. |
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{Sommerhalder2003, 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. |
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{Shen2003, 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. |
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. |
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. |
Junji Ito; Andrey R. Nikolaev; Marjolein Luman; Maartje F. Aukes; Chie Nakatani; Cees Van Leeuwen Perceptual switching, eye movements, and the bus paradox Journal Article In: Perception, vol. 32, no. 6, pp. 681–698, 2003. @article{Ito2003, According to a widely cited finding by Ellis and Stark (1978 Perception 7 575-581), the duration of eye fixations is longer at the instant of perceptual reversal of an ambiguous figure than before or after the reversal. However, long fixations are more likely to include samples of an independent random event than are short fixations. This sampling bias would produce the pattern of results also when no correlation exists between fixation duration and perceptual reversals. When an appropriate correction is applied to the measurement of fixation durations, the effect disappears. In fact, there are fewer actual button-presses during the long intervals than would be expected by chance. Moving-window analyses performed on eye-fixation data reveal that no unique eye event is associated with switching behaviour. However, several indicators, such as blink frequency, saccade frequency, and the direction of the saccade, are each differentially sensitive to perceptual and response-related aspects of the switching process. The time course of these indicators depicts switching behaviour as a process of cascaded stages. |
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. |
Johanna K. Kaakinen; Jukka Hyönä; Janice M. Keenan How prior knowledge, WMC, and relevance of information affect eye fixations in expository text Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 29, pp. 447–457, 2003. @article{Kaakinen2003, This study examined how prior knowledge and working memory capacity (WMC) influence the effect of a reading perspective on online text processing. In Experiment 1, 47 participants read and recalled 2 texts of different familiarity from a given perspective while their eye movements were recorded. The participants' WMC was assessed with the reading span test. The results suggest that if the reader has prior knowledge related to text contents and a high WMC, relevant text information can be encoded into memory without extra processing time. In Experiment 2, baseline processing times showed whether readers slow down their processing of relevant information or read faster through their relevant information. The results are discussed in the light of different working memory theories. |
Yuki Kamide; Gerry T. M. Altmann; Sarah L. Haywood The time-course of prediction in incremental sentence processing: Evidence from anticipatory eye movements Journal Article In: Journal of Memory and Language, vol. 49, no. 1, pp. 133–156, 2003. @article{Kamide2003, Three eye-tracking experiments using the 'visual-world' paradigm are described that explore the basis by which thematic dependencies can be evaluated in advance of linguistic input that unambiguously signals those dependencies. Following Altmann and Kamide (1999), who found that selectional information conveyed by a verb can be used to anticipate an upcoming Theme, we attempt to draw here a more precise picture of the basis for such anticipatory processing. Our data from two studies in English and one in Japanese suggest that (a) verb-based information is not limited to anticipating the immediately following (grammatical) object, but can also anticipate later occurring objects (e.g., Goals), (b) in combination with information conveyed by the verb, a pre-verbal argument (Agent) can constrain the anticipation of a subsequent Theme, and (c) in a head-final construction such as that typically found in Japanese, both syntactic and semantic constraints extracted from pre-verbal arguments can enable the anticipation, in effect, of a further forthcoming argument in the absence of their head (the verb). We suggest that such processing is the hallmark of an incremental processor that is able to draw on different sources of information (some non-linguistic) at the earliest possible opportunity to establish the fullest possible interpretation of the input at each moment in time. |
Yuki Kamide; Christoph Scheepers; Gerry T. M. Altmann Integration of syntactic and semantic information in predictive processing: Cross-linguistic evidence from German and English Journal Article In: Journal of Psycholinguistic Research, vol. 32, no. 1, pp. 37–55, 2003. @article{Kamide2003a, Two visual-world eyetracking experiments were conducted to investigate whether, how, and when syntactic and semantic constraints are integrated and used to predict properties of subsequent input. Experiment 1 contrasted auditory German constructions such as, "The hare-nominative eats ... (the cabbage-acc)" versus "The hare-accusative eats ... (the fox-nom)," presented with a picture containing a hare, fox, cabbage, and distractor. We found that the probabilities of the eye movements to the cabbage and fox before the onset of NP2 were modulated by the case-marking of NP1, indicating that the case-marking (syntactic) information and verbs' semantic constraints are integrated rapidly enough to predict the most plausible NP2 in the scene. Using English versions of the some stimuli in active/passive voice (Experiment 2), we replicated the same effect, but at a slightly earlier position in the sentence. We discuss the discrepancies in the two Germanic languages in terms of the ease of integrating information across, or within, constituents. |
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. |
Caroline J. Ketcham; Timothy L. Hodgson; Christopher Kennard; George E. Stelmach Memory-motor transformations are impaired in Parkinson s disease Journal Article In: Experimental Brain Research, vol. 149, pp. 30–39, 2003. @article{Ketcham2003, Parkinson's disease patients are known to suffer loss of dopaminergic input to the rostral caudate nucleus. Recent functional magnetic resonance imaging (fMRI) studies have implicated this structure in the transformation of spatial information in memory to guide action, suggesting that memory to motor transformations may be selectively impaired in Parkinson's disease. In order to investigate this possibility we tested a group of Parkinson's disease patients (PDs) using a memory- guided pointing task. Of interest was whether patients showed reduced accuracy in the task as a function of memory load. Twelve PD patients and 13 elderly controls were asked to recall single or four step target sequences with 2 time delays (500 and 3,500 ms). In all memory- guided conditions PD patients showed increased variabil- ity in memory-guided movement end-points. This effect was not affected by delay, number of items, or the sequence familiarity. The results are consistent with increased variability in memory-motor transformations in early PD, due to dopamine depletion within the rostral caudate nucleus. |
Willem P. A. Kelders; Gert Jan Kleinrensink; Josef N. Geest; Louw Feenstra; Chris I. De Zeeuw; Maarten A. Frens Compensatory increase of the cervico-ocular reflex with age in healthy humans Journal Article In: Journal of Physiology, vol. 553, no. 1, pp. 311–317, 2003. @article{Kelders2003, The cervico-ocular reflex (COR) is an ocular stabilization reflex that is elicited by rotation of the neck. It works in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) in order to prevent visual slip over the retina due to self-motion. The gains of the VOR and OKR are known to decrease with age. We have investigated whether the COR, a reflexive eye movement elicited by rotation of the neck, shows a compensatory increase and whether a synergy exists between the COR and the other ocular stabilization reflexes. In the present study 35 healthy subjects of varying age (20-86 years) were rotated in the dark in a trunk-to-head manner (the head fixed in spaced with the body passively rotated under it) at peak velocities between 2.1 and 12.6 deg s-1 as a COR stimulus. Another 15 were subjected to COR, VOR and OKR stimuli at frequencies between 0.04 and 0.1 Hz. Three subjects participated in both tests. The position of the eyes was recorded with an infrared recording technique. We found that the COR-gain increases with increasing age and that there is a significant covariation between the gains of the VOR and COR, meaning that when VOR increases, COR decreases and vice versa. A nearly constant phase lag between the COR and the VOR of about 25 deg existed at all stimulus frequencies. |
Dirk Kerzel Mental extrapolation of target position is strongest with weak motion signals and motor responses Journal Article In: Vision Research, vol. 43, no. 25, pp. 2623–2635, 2003. @article{Kerzel2003, Some accounts hold that the position of moving objects is extrapolated either in visual perception or visual short-term memory ("representational momentum"). However, some studies did not find forward displacement of the final position when smooth motion was used, whereas reliable displacement was observed with implied motion. To resolve this conflict, the frequency of position changes was varied to sample motion types between the extreme cases of implied and smooth motion. A continuous function relating frequency of target change and displacement was found: Displacement increased when the frequency of position changes was reduced. Further, the response mode was varied. Probe judgments produced less forward displacement than motor judgments such as mouse or natural pointing movements. Also, localization judgments were susceptible to motion context, but not to variations of probe shape or expectancy about trajectory length. It is suggested that forward displacement results from the extrapolation of the next step in the observed motion sequence. |
Dirk Kerzel; Karl R. Gegenfurtner Neuronal processing delays are compensated in the sensorimotor Journal Article In: Current Biology, vol. 13, no. 22, pp. 1975–1978, 2003. @article{Kerzel2003a, Moving objects change their position until signals from the photoreceptors arrive in the visual cortex. Nonetheless, motor responses to moving objects are accurate and do not lag behind the real-world position. The questions are how and where neural delays are compensated for. It was suggested that compensation is achieved within the visual system by extrapolating the position of moving objects. A visual illusion supports this idea: when a briefly flashed object is presented in the same position as a moving object, it appears to lag behind. However, moving objects do not appear ahead of their final or reversal points. We investigated a situation where participants localized the final position of a moving stimulus. Visual perception and short-term memory of the final target position were accurate, but reaching movements were directed toward future positions of the target beyond the vanishing point. Our results show that neuronal latencies are not compensated for at early stages of visual processing, but at a late stage when retinotopic information is transformed into egocentric space used for motor responses. The sensorimotor system extrapolates the position of moving targets to allow for precise localization of moving targets despite neuronal latencies. |
Elizabeth Gilman; Geoffrey Underwood Restricting the field of view to investigate the perceptual spans of pianists Journal Article In: Visual Cognition, vol. 10, no. 2, pp. 201–232, 2003. @article{Gilman2003, An experiment is reported, which was designed to determine how the perceptual span of pianists varies with developing skill and cognitive load. Eye-movements were recorded as musical phrases were presented through a gaze-contingent window, which contained one beat, two beats, or four beats. In a control condition, the music was presented without a window. The pianists were required to perform three tasks of varying cognitive load: An error-detection task (low load); a sight- reading task (medium load); and a transposition task (high load). Measures taken comprised fixation duration, fixation frequency, saccade length, fixation locations, performance duration, note duration, position of first error, number of errors, and eye±hand span. The results indicate that good and poor sight-readers do not differ in terms of perceptual span. However, good sight-readers were found to have larger eye±hand spans. Furthermore, the results show that increasing cognitive load decreases eye±hand span, but has little effect on perceptual span. |
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. |
Valérie Gaveau; Olivier Martin; Claude Prablanc; Denis Pélisson; Christian Urquizar; Michel Desmurget On-line modification of saccadic eye movements by retinal signals Journal Article In: Neuroreport, vol. 14, no. 6, pp. 875–878, 2003. @article{Gaveau2003, A saccade is a rapid shift of the position of the eyes (<100ms). Saccades are generally considered too quick to be inpoundsuenced by retinal signals.To address this idea, we displaced the visual target of a rightward horizontal saccade at eye movement onset (when there is suppression of conscious perception).To prevent adaptive and learning e¡ects to occur, jump saccadeswere always followed by a random series of 10 no-jump saccades. Results indicated that the target jump influenced significantly the amplitude and the peak velocity of the ongoing saccade (opposite e¡ects were found for rightward and leftward jumps). Changes in saccade kinematics occurred as early as 50ms after the target jump. These results show that retinal information is processed quickly during eye movements, presumably through sub-cortical pathways. |
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. |
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. |
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. |
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. |
Tomas Lindberg; Risto Näsänen The effect of icon spacing and size on the speed of icon processing in the human visual system Journal Article In: Displays, vol. 24, no. 3, pp. 111–120, 2003. @article{Lindberg2003, Alphanumeric and graphical information needs to be presented in such a way that its perception is accurate, fast and as effortless as possible. This study investigated the effects of spacing and size of individual interface elements on their perception. Experiment 1 investigated the effect of icon spacing on the speed of visual search for a target icon and determined the perceptual span for icons, that is, the number of icons that can be processed by one eye fixation. Experiment 2 studied the effect of size, and experiment 3 the subjective preferences for levels of icon spacing. The results of experiment 1 showed that spacing does not have an effect on search times. On average the perceptual span for icons was found to be 25 arranged in a 5 × 5 array. The size of the interface elements, on the other hand, was found to have a great effect. Icons smaller than 0.7° resulted in significantly raised search times. Experiment 3 revealed that an inter-element spacing of one icon is to be preferred and a spacing of zero icons is to be avoided. |
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. |
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. |
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. |
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. |
Kathryn Bock; David E. Irwin; Douglas J. Davidson; Willem J. M. Levelt Minding the clock Journal Article In: Journal of Memory and Language, vol. 48, no. 4, pp. 653–685, 2003. @article{Bock2003, Telling time is an exercise in coordinating language production with visual perception. By coupling different ways of saying times with different ways of seeing them, the performance of time-telling can be used to track cognitive transformations from visual to verbal information in connected speech. To accomplish this, we used eyetracking measures along with measures of speech timing during the production of time expressions. Our findings suggest that an effective interface between what has been seen and what is to be said can be constructed within 300 ms. This interface underpins a preverbal plan or message that appears to guide a comparatively slow, strongly incremental formulation of phrases. The results begin to trace the divide between seeing and saying - or thinking and speaking - that must be bridged during the creation of even the most prosaic utterances of a language. |
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. |
Benjamin T. Backus; Daniel Matza-Brown The contribution of vergence change to the measurement of relative disparity Journal Article In: Journal of Vision, vol. 3, no. 11, pp. 727–750, 2003. @article{Backus2003, The relative disparity between two objects in a scene can in principle be measured directly from the retinal images, without knowledge of eye position. But relative disparity increment thresholds are lowest when the relative disparity is small and the objects are not widely separated in the visual field: thus, some relative disparities are easier for the visual system to measure than others. We consider, after others, a second method by which the visual system could measure relative disparity, based on change in vergence ("delta vergence" or DV). The DV mechanism could be more reliable than the retinal mechanism when visual targets are widely separated in visual direction or depth. We used a cue-conflict paradigm to measure the extent to which perceived depth depends on DV. As target separation increased, so did reliance on DV. As intertarget disparity increased, reliance on DV increased for one observer but not for two others. |
Richard Amlôt; Robin Walker; Jon Driver; Charles Spence Multimodal visual–somatosensory integration in saccade generation Journal Article In: Neuropsychologia, vol. 41, no. 1, pp. 1–15, 2003. @article{Amlot2003, Neurophysiological studies have demonstrated multisensory interaction effects in the neural structures involved in saccade generation when visual, auditory or somatosensory stimuli are presented bimodally. Visual–auditory interaction effects have been demonstrated in numerous behavioural studies of saccades but little is known about interaction effects involving somatosensory stimuli. The present study examined visual–somatosensory interaction effects on saccade generation using a multisensory paradigm, whereby task-irrelevant distractors appeared spatially-coincident with, or remote from the designated saccade target. Somatosensory distractors reduced the latency of saccades when presented before the visual target and the greatest facilitation effectwas observed with spatially-coincident stimuli.Visual distractors spatially-coincident with a somatosensory target reduced latency (and increased peak velocity) when presented before and after the target.Visual distractors contralateral to somatosensory targets increased saccade latency and produced high error rates of saccades made to the distractor. The high error rates and latencymodulation with visual distractors is consistent with a bias for visual stimuli in the saccadic system. In the visual target condition, saccade latency was modulated by a somatosensory distractor that was entirely task-irrelevant and this effect was always greatest with spatially-coincident distractors. The multisensory distractor effects are discussed in terms of saccades being programmed to the non-target modality, the early triggering of a non-spatial saccade ‘when' signal, and multisensory neuronal enhancement effects. |