Sebastian Pannasch; Sascha M. Dornhoefer; Pieter J. A. Unema; Boris M. Velichkovsky
In: Vision Research, vol. 41, no. 25-26, pp. 3345–3351, 2001.
Presenting a distractor prolongs not only saccadic reaction times in paced tasks but also fixation durations in unpaced tasks. To investigate whether the effect of a distractor is a pure optomotor reflex, we used both visual and auditory distractors in an unpaced picture-viewing paradigm. Results show a distractor effect for both modalities. Analysis of data from previous studies showed similar effects, even in amodal shifts of attention. These findings challenge the hypothesis that the effect is modality-specific and suggest that the distractor effect may be another expression of the orienting reflex.
Marc Pomplun; Eyal M. Reingold; Jiye Shen
In: Vision Research, vol. 41, no. 21, pp. 2757–2769, 2001.
The present study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing conditions, the information shown outside the gaze-contingent window was restricted to the feature or feature pair shared between the target and a particular distractor type. In the masking conditions, no stimulus features were shown outside the window. Significant cueing and masking effects on saccadic selectivity were observed for saccades directed at items within the window, where all features were visible across experimental conditions. Cueing a particular feature or feature pair biased saccadic selectivity towards this feature or feature pair, while masking generally reduced saccadic selectivity. These findings support the concept of visual guidance being a preattentive process that operates in parallel across the display.
Marc Pomplun; Eyal M. Reingold; Jiye Shen
In: Cognition, vol. 81, no. 2, pp. B57–B67, 2001.
In three experiments, participants' visual span was measured in a comparative visual search task in which they had to detect a local match or mismatch between two displays presented side by side. Experiment 1 manipulated the difficulty of the comparative visual search task by contrasting a mismatch detection task with a substantially more difficult match detection task. In Experiment 2, participants were tested in a single-task condition involving only the visual task and a dual-task condition in which they concurrently performed an auditory task. Finally, in Experiment 3, participants performed two dual-task conditions, which differed in the difficulty of the concurrent auditory task. Both the comparative search task difficulty (Experiment 1) and the divided attention manipulation (Experiments 2 and 3) produced strong effects on visual span size.
Keith Rayner; Caren M. Rotello; Andrew J. Stewart; Jessica Keir; Susan A. Duffy
In: Journal of Experimental Psychology: Applied, vol. 7, no. 3, pp. 219–226, 2001.
Viewers looked at print advertisements as their eye movements were recorded. Half of them were told to pay special attention to car ads, and the other half were told to pay special attention to skin-care ads. Viewers tended to spend more time looking at the text than the picture part of the ad, though they did spend more time looking at the type of ad they were instructed to pay attention to. Fixation durations and saccade lengths were both longer on the picture part of the ad than the text, but more fixations were made on the text regions. Viewers did not alternate fixations between the text and picture part of the ad, but they tended to read the large print, then the smaller print, and then they looked at the picture (although some viewers did an initial cursory scan of the picture). Implications for (a) how viewers integrate pictorial and textual information and (b) applied research and advertisement development are discussed.
Eyal M. Reingold; Neil Charness; Marc Pomplun; Dave M. Stampe
Visual span in expert chess players: Evidence from eye movements Journal Article
In: Psychological Science, vol. 12, no. 1, pp. 48–55, 2001.
The reported research extends classic findings that after briefly viewing structured, but not random, chess positions, chess masters reproduce these positions much more accurately than lessskilled players. Using a combination of the gaze-contingent window paradigm and the change blindness flicker paradigm, we documented dramatically larger visual spans for experts while processing structured, but not random, chess positions. In addition, in a checkdetection task, a minimized 3 × 3 chessboard containing a King and potentially checking pieces was displayed. In this task, experts made fewer fixations per trial than less-skilled players, and had a greater proportion of fixations between individual pieces, rather than on pieces. Our results provide strong evidence for a perceptual encoding advantage for experts attributable to chess experience, rather than to a general perceptual or memory superiority.
John F. Soechting; Kevin C. Engel; Martha Flanders
The Duncker Illusion and eye–hand coordination Journal Article
In: Journal of Neurophysiology, vol. 85, no. 2, pp. 843–854, 2001.
A moving background alters the perceived direction of target motion (the Duncker illusion). To test whether this illusion also affects pointing movements to remembered/extrapolated target locations, we constructed a display in which a target moved in a straight line and disappeared behind a band of moving random dots. Subjects were required to touch the spot where the target would emerge from the occlusion. The four directions of random-dot motion induced pointing errors that were predictable from the Duncker illusion. Because it has been previously established that saccadic direction is influenced by this illusion, gaze was subsequently recorded in a second series of experiments while subjects performed the pointing task and a similar task with eye-tracking only. In the pointing task, subjects typically saccaded to the lower border of the occlusion zone as soon as the target disappeared and then tried to maintain fixation at that spot. However, it was particularly obvious in the eye-tracking-only condition that horizontally moving random dots generally evoked an appreciable ocular following response, altering the gaze direction. Hand-pointing errors were related to the saccadic gaze error but were more highly correlated with final gaze errors (resulting from the initial saccade and the subsequent ocular following response). The results suggest a model of limb control in which gaze position can provide the target signal for limb movement.
Jean Saint-Aubin; Raymond M. Klein
Influence of parafoveal processing on the missing letter effect Journal Article
In: Journal of Experimental Psychology: Human Perception and Performance, vol. 27, no. 2, pp. 318–334, 2001.
According to the parafoveal-processing hypothesis, letters are more often missed in function words than in content words because the former are more likely to be identified in the parafovea, where letter processing is not available. Contrary to previous demonstrations, more omissions occurred in function words than in content words when parafoveal processing was not available because words were displayed in column format, text was read through a 5-letter window, or words were presented 1 at a time on a computer screen. In all experiments, impeding parafoveal processing decreased omission rates for function but not for content words. In the last experiment, direct monitoring of eye movements revealed that, for both fixated and skipped words, letters in function words are missed more often than content words. These results are best interpreted within a model including the structural precedence hypothesis and stressing the importance of visual factors.
Risto Näsänen; Jan Karlsson; Helena Ojanpää
Display quality and the speed of visual letter search Journal Article
In: Displays, vol. 22, no. 4, pp. 107–113, 2001.
Previously it has been suggested that visual search tasks can be used to evaluate the perceptual quality of display devices with respect to their ability to convey alphanumeric information. The purpose of the present study was to examine how character size and contrast used in a visual search test affects its sensitivity to differences in the quality of display devices. The task of the observer was to search for, and identify, an uppercase letter from a rectangular array of characters in which the other items were numerals. Threshold search time, that is, the duration of stimulus presentation required for search that is successful with a given probability, was determined by using a multiple-alternative staircase method. Eye movements were recorded simultaneously by using a fast video eye tracker. Threshold search times were measured as a function of character size at two contrast levels using a CRT and an LCD display. For all experimental conditions, threshold search time decreased with increasing letter size. This was accompanied with a decrease in the number of eye fixations per search as well as a decrease of fixation duration. At high contrast (CMichelson≈ 1), no statistically significant difference was found between the two displays. However, at the lower contrast used (CMichelson≈ 0.2) and at small character sizes, threshold search times for the CRT display were clearly longer and the number of fixations per search was higher than for the LCD display. In conclusion, visual letter search is a more sensitive method for display evaluation at small contrasts and with small character sizes.
Risto Näsänen; Helena Ojanpää; Ilpo Kojo
In: Vision Research, vol. 41, no. 14, pp. 1817–1824, 2001.
According to the visual span control hypothesis, eye movements are controlled in relation to the size of visual span. In reading, the decrease of contrast reduces visual span, saccade sizes, and reading speed. The purpose of the present study is to determine how stimulus contrast affects the speed of two-dimensional visual search and how changes in eye movements and visual span could explain changes in performance. The task of the observer was to search for, and identify, an uppercase letter from a rectangular array of characters in which the other items were numerals. Threshold search time, i.e. the duration of stimulus presentation required for search that is successful with a given probability, was determined by using a multiple-alternative staircase method. Eye movements were recorded simultaneously by using a video eye tracker. Four different set sizes (the sizes of stimulus array) (3 × 3-10 × 10), and five different contrasts (0.0186 - 0.412) were used. At all set sizes, threshold search time decreased with increasing contrast. Also the average number of fixations per search decreased with increasing contrast. At the smallest set size (3 × 3), only one fixation was needed except at the lowest contrast. Average fixation duration decreased and saccade amplitudes increased slightly with increasing contrast. The reduction of the number of fixations with increasing contrast suggests that visual span, i.e. the area from which information can be collected at one fixation, increases with increasing contrast. The reduction of the number of fixations together with reduced fixation duration result in reduced search times when contrast increases.
Sebastiaan F. W. Neggers; Harold Bekkering
In: Journal of Neurophysiology, vol. 86, no. 2, pp. 961–970, 2001.
A well-coordinated pattern of eye and hand movements can be observed during goal-directed arm movements. Typically, a saccadic eye movement precedes the arm movement, and its occurrence is temporally correlated with the start of the arm movement. Furthermore, the coupling of gaze and aiming movements is also observable after pointing initiation. It has recently been observed that saccades cannot be directed to new target stimuli, away from a pointing target stimulus. Saccades directed to targets presented during the final phase of a pointing movement were delayed until after pointing movement offset (“gaze anchoring”). The present study investigated whether ocular gaze is anchored to a pointing target during the entire pointing movement. In experiment 1, new targets were presented at various times during the duration of a pointing movement, triggered by the kinematics arm moment itself (movement onset, peak acceleration/velocity/deceleration, and offset). Subjects had to make a saccade to the new target as fast as possible while maintaining the pointing movement to the initial target. Saccadic latencies were increased by an amount of time that approximately equaled the remaining pointing time after saccadic target presentation, with the majority of saccades executed after pointing movement offset. The nature of the signal driving gaze stabilization during pointing was investigated in exper- iment 2. In previous experiments where ocular gaze was anchored to a pointing target, subjects could always see their moving arm, thus it was unknown whether a visual image of the moving arm, an afferent (proprioceptive) signal or an efferent (motor control related) signal produced gaze anchoring. In experiment 2 subjects had to point with or without vision of the moving arm to test whether a visual signal is used to anchor gaze to a pointing target. Results indicate that gaze anchoring was also observed without vision of the moving arm. The findings support the existence of a mechanism enforcing ocular gaze anchoring during the entire duration of a pointing movement. Moreover, such a mechanism uses an internally generated, or proprioceptive, nonvisual signal. Possible neural substrates underlying these processes are discussed, as well as the role of selective attention.
Elliot M. Frohman; Teresa C. Frohman; J. Fleckenstein; M. K. Racke; K. Hawker; Phillip D. Kramer
In: Journal of Neurology, Neurosurgery and Psychiatry, vol. 70, no. 5, pp. 688–692, 2001.
The objective was to describe in multiple sclerosis, a cerebellar eye movement syndrome that resulted from an acute episode of inflammatory demyelination. Contrapulsion is an ocular motor disturbance characterised by a triad of (1) hypermetric saccadic eye movements in a direction opposite from a precisely localised lesion within a specific white matter pathway, the uncinate fasciculus, at the level of the superior cerebellar peduncle (SCP); (2) hypometric saccades towards the side of the lesion; (3) oblique saccades directed away from the side of the lesion on attempted vertical saccades. Infrared oculography was used to demonstrate the characteristic features of contrapulsion in two patients with multiple sclerosis. Brain MRI showed lesions within the region of the uncinate fasciculus and superior cerebellar peduncle in both patients. Eye movement recordings showed saccadic hypermetria away from the side of the lesion and saccadic hypometria towards the side of the lesion. The hypometria decomposed into a series of stepwise movements as the eye approached the target. Oblique saccades directed away from the side of the lesion were seen on attempted vertical saccades. In conclusion, ocular contrapulsion can be seen in patients with multiple sclerosis and results from a lesion in the region of the SCP, involving the uncinate fasciculus.
Elliot M. Frohman; H. Zhang; Phillip D. Kramer; J. Fleckenstein; K. Hawker; M. K. Racke; Teresa C. Frohman
In: Neurology, vol. 57, no. 5, pp. 762–768, 2001.
OBJECTIVE: The authors imaged the medial longitudinal fasciculus (MLF) in 58 patients with MS and chronic internuclear ophthalmoparesis (INO) to determine which MRI technique best shows the characteristic lesion associated with this ocular motor syndrome. METHODS: Using quantitative infrared oculography, the authors determined the ratios of abduction to adduction for velocity and acceleration, to confirm the presence of INO and to determine the severity of MLF dysfunction in 58 patients with MS and INO. Conventional MRI techniques, including proton density imaging (PDI), T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR) imaging, were used to ascertain which technique best shows MLF lesions within the brainstem tegmentum. T1-weighted imaging was performed to determine the frequency of brainstem tegmentum hypointensities. RESULTS: All patients studied had evidence of an MLF lesion hyperintensity on PDI, whereas T2-weighted imaging and FLAIR imaging showed these lesions in 88% and 48% of patients, respectively. With PDI, dorsomedial tegmentum lesions were seen in the pons in 93% of patients and in the midbrain of 66% of patients. Lesions were observed at both locations in 59% of patients. One patient had an MLF lesion with a corresponding T1 hypointensity. CONCLUSIONS: PDI best shows the MLF lesion in patients with MS and INO.
Melanie Doyle; Robin Walker
In: Experimental Brain Research, vol. 139, no. 3, pp. 333–344, 2001.
In this study we examined the impact of irrelevant distractors upon trajectories of reflexive and voluntary saccades. Observers made saccades to visual targets above and below fixation as directed by target appearance (reflexive) or by a central directional cue (voluntary) in the presence of an irrelevant distractor stimulus (a cross) whose appearance was simultaneous with target onset. We recorded saccade latency, amplitude and the magnitude of saccade curvature relative to the direct route from the start-to-end of the saccade. Previous studies of saccades curvature have used distractors to provide information about the saccade task and, as a result, have only examined trajectories of voluntary saccades. However, we have shown that both reflexive and voluntary saccades curved away from irrelevant distractors. The effect of irrelevant distractors indicates that observers do not need to attend to distractors in a voluntary fashion for distractors to modify saccade trajectories. Furthermore, it highlights an important parallel in curvature of saccades and reach trajectories, namely that both curve away from irrelevant distractors. The second important observation was that reflexive, as well as voluntary, saccades curved away from distractors. This suggests that curvature is not solely a consequence of voluntary control. These results have been considered within the context of inhibition-based theories of curvature derived from studies of saccade and manual reach trajectories.
Gary Feng; Kevin Miller; Hua Shu; Houcan Zhang
In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 27, no. 4, pp. 1079–1100, 2001.
To examine how readers of Chinese and English take advantage of orthographic and phonological features in reading, the authors investigated the effects of spelling errors on reading text in Chinese and English using the error disruption paradigm of M. Daneman and E. Reingold (1993). Skilled readers in China and the United States read passages in their native language that contained occasional spelling errors. Results showed that under some circumstances very early phonological activation can be identified in English, but no evidence for early phonology was found in Chinese. In both languages, homophone errors showed a benefit in measures of later processing, suggesting that phonology helps readers recover from the disruptive effects of errors. These results suggest that skilled readers take advantage of the special features of particular orthographies but that these orthographic effects may be most pronounced in the early stages of lexical access.
Diane C. Gooding; Kathleen A. Tallent
In: Journal of Nervous and Mental Disease, vol. 189, no. 1, pp. 8–16, 2001.
To date, the research literature has yielded conflicting reports regarding the specificity of antisaccade deficits to schizophrenia. We sought to examine antisaccade and working memory task performance in schizophrenia patients and bipolar patients, as well as to examine the relationship between the two tasks in both patient populations. Thirty-four schizophrenia patients, 20 bipolar patients, and 30 nonpatient controls were administered saccadic inhibition (antisaccade), working memory, and sensorimotor tasks. Compared with the controls, the schizophrenia patients displayed both antisaccade deficits and working memory deficits. In contrast, the bipolar patients produced significantly more errors on the antisaccade task than the controls, though the bipolar group performed similarly to the control group on the working memory task. Mediational analyses demonstrated that working memory partially mediates the relationship between patients' diagnostic group status and antisaccade task performance; working memory performance contributed uniquely to the prediction of antisaccade task performance in the two patient groups. Antisaccade deficits do not appear specific to schizophrenia. The results suggest that in schizophrenia, working memory and antisaccade tasks are tapping similar cognitive processes, whereas in bipolar patients the processes underlying antisaccade and working memory performance are disparate.
Harold H. Greene; Keith Rayner
Eye movements and familiarity effects in visual search Journal Article
In: Vision Research, vol. 41, no. 27, pp. 3763–3773, 2001.
Familiarity with the distractors around an unfamiliar target facilitates visual search. Three Experiments examined whether the effect occurs because fixations are (a) shorter and fewer, (b) shorter, but more abundant, (c) equally long, but fewer, or (d) longer, but fewer when distractors are familiar. Results indicated comparably long, but fewer fixations when distractors are familiar. Hence, the theory that unfamiliar distractors need longer processing is discounted. In a fourth Experiment, a gaze-contingent moving window paradigm was used to control peripheral processing. Results revealed a wider span of effective processing for familiar distractors. A hypothesis based on low-level physiological processes is introduced to account for the familiarity effect.
Harold H. Greene; Keith Rayner
Eye-movement control in direction-coded visual search Journal Article
In: Perception, vol. 30, no. 2, pp. 147–157, 2001.
Subjects searched for a target among distractors which were arranged randomly or such that each distractor provided information about the relative position of a target. Trials were presented either in a blocked design (so that the subjects knew a priori the contextual information in the display) or in a mixed design. When the distractors provided information about target position, there were (i) shorter manual RTs, (ii) fewer fixations made in search of the target, (iii) longer mean fixation durations, (iv) shorter initial fixation durations, (v) shorter mean gaze shifts, (vi) a smaller area of fixation dispersion, and (vii) a greater percentage of optimally directed saccades. Except for gaze shifts, the results were uninfluenced by whether or not there was a blocked or a mixed presentation. The results of the study suggest that despite noise in the search mechanism, fixation durations were adjusted to process directly the currently fixated element(s).
David A. Leopold; Alice J. O. Toole; Thomas Vetter; Volker Blanz
In: Nature Neuroscience, vol. 4, no. 1, pp. 89–94, 2001.
We used high-level configural aftereffects induced by adaptation to realistic faces to investigate visual representations underlying complex pattern perception. We found that exposure to an individual face for a few seconds generated a significant and precise bias in the subsequent perception of face identity. In the context of a computationally derived 'face space,' adaptation specifically shifted perception along a trajectory passing through the adapting and average faces, selectively facilitating recognition of a test face lying on this trajectory and impairing recognition of other faces. The results suggest that the encoding of faces and other complex patterns draws upon contrastive neural mechanisms that reference the central tendency of the stimulus category.
Adrienne L. LeVasseur; J. Randall Flanagan; Richard J. Riopelle; Douglas P. Munoz
In: Brain, vol. 124, pp. 2045–2058, 2001.
Tourette's syndrome is characterized by involuntary tics and, although the underlying pathogenesis and patho- physiology of Tourette's syndrome remains unclear, it is suspected that basal ganglia structures are involved. The basal ganglia also play an important role in the control of saccadic eye movements and we therefore hypothesize that Tourette's syndrome patients have abnormal control of saccadic eye movements. In this study, 10 subjects with Tourette's syndrome and 10 age- and sex-matched controls performed four different oculomotor paradigms requiring the execution and/or suppression of reflexive and/or voluntary saccades. In the immediate saccade tasks, sub- jects were required to look either toward (pro-saccade task) or away from (anti-saccade task) a peripheral target as soon as it appeared. In the delayed saccade tasks, subjects were instructed to wait for a central fixation point to disappear before initiating eye movements. Among Tourette's syndrome subjects, saccadic reaction times were longer in all tasks. Saccadic amplitudes were smaller in Tourette's syndrome subjects, and they made more saccades to reach the eccentric target. The occurrence of direction errors (i.e. reflexive pro-saccades on anti-saccade trials) was normal in the immediate anti-saccade task, suggesting that the ability to inhibit reflexive saccades towards novel stimuli was not impaired in Tourette's syndrome. Timing errors (i.e. eye movements made prior to disappearance of the central fixation point in delayed saccade tasks) were significantly greater among Tourette's syndrome subjects. Moreover, these errors were predominantly made towards the first target of the remembered sequence in a delayed memory-guided sequential saccade task. These results indicate that the ability to inhibit or delay planned motor programmes is significantly impaired in Tourette's syndrome. We hypothesize that altered cortical–basal ganglia circuitry leads to reduced cortical inhibition making it harder for Tourette's syndrome subjects to withhold the execution of planned motor programmes.
Ch. Klein; P. Berg
In: Psychophysiology, vol. 38, no. 4, pp. 704–711, 2001.
The aim of the present study was the comparative assessment of the 4-week test-retest stabilities of the saccadic CNV (sCNV) and saccadic reaction times (SRT) during the execution of pro- and antisaccades, as well as the stability of RT during execution of two neuropsychological tests of alertness and S-R incompatibility. Prosaccades were elicited under the 200-ms gap and overlap conditions, antisaccades under the overlap condition (64 trials each). The EEG was recorded from 25 channels with a DC amplifier (MES, Munich). Data of 20 healthy participants were statistically analyzed. We found high test-retest correlations for all SRT (.76 < or = r(tt) < or = .88) and neuropsychological (.62 < or = r(tt) < or = .88) measures. For the sCNV, coefficients ranging between .58 (pro/gap) and .77 (anti/overlap) were obtained. Whereas SRT were significantly faster during the second than during the first session, group means for the saccadic CNV were stable across the sessions. Our results suggest high 4-week stability of individual differences in SRT, and moderate to good stabilities of saccadic CNV amplitudes. Our results recommend these "traitlike" measures to be used in individual differences research.
Arthur F. Kramer; Nicholas D. Cassavaugh; David E. Irwin; Matthew S. Peterson; Sowon Hahn
In: Perception and Psychophysics, vol. 63, no. 6, pp. 952–968, 2001.
In three experiments, we examined attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside of it. In Experiment 1, task-irrelevant sudden onsets appeared simultaneously on half the trials with the presentation of the color singleton target. Response times (RTs) were longer when onsets appeared in the display regardless of the number of onsets. Eye-scan strategies were also disrupted by the appearance of the onset distractors, although the proportion of trials on which the eyes were directed to the onsets was the same regardless of the number of onsets. In Experiment 2, we manipulated the time of presentation of two task-irrelevant onsets in order to further examine whether multiple onsets would be attended and fixated prior to attending a color singleton target. Again, subjects made a saccade to a task-irrelevant onset on a substantial proportion of trials prior to fixating the target. However, saccades to the second onset were rare. Experiment 3 served as a replication of Experiment 1 but without the requirement for subjects to move their eyes to detect and identify the singleton target. The RT results were consistent with those in Experiment 1; dual onsets had no larger an effect on response speed than single onset distractors. These data are discussed in terms of the interaction between top-down and bottom-up control of attention and the eyes.
Avital Deutsch; Shlomo Bentin
In: Journal of Memory and Language, vol. 45, no. 2, pp. 200–224, 2001.
The interrelation between syntactic analysis of agreement and semantic processing was examined by recording eye movements and event-related potentials. Subject-predicate gender agreement was manipulated within Hebrew sentences. The subject was either animate or inanimate, with conceptual gender denoted by the subject's morphological structure. First-pass reading time was found to be longer for incongruent predicates than of congruent predicates but only if the predicate's gender was morphologically marked. Furthermore, this effect was larger in the animate than in the inanimate condition. Second-pass reading time was also prolonged by gender incongruity but this effect was not affected by either markedness or animacy. Gender incongruity enhanced the amplitude of an early negative potential (ostensibly ELAN), of a later negative potential (N400), and of a positive potential (P600). Like first-pass reading time, the congruity effect on the syntactically modulated P600 was significant only for marked predicates, but it did not interact with animacy. In contrast, the congruity effect on the semantically modulated N400 was significant only in the animate condition. The N400 was not affected by markedness. The congruity effect on the early negativity did not interact with either animacy or markedness. The interaction between semantic and syntactic processing and its time course are discussed within the framework set by interactive, constraint-based models for online sentence processing.
Neil Charness; Eyal M. Reingold; Marc Pomplun; Dave M. Stampe
In: Memory and Cognition, vol. 29, no. 8, pp. 1146–1152, 2001.
Expert and intermediate chess players attempted to choose the best move in five chess positions while their eye movements were monitored. Experts were faster and more accurate than intermediates in choosing the best move. Experts made fewer fixations per trial and greater amplitude saccades than did intermediates, but there was no difference in fixation duration across skill groups. Examining the spatial distribution of the first five fixations for each position by skill group revealed that experts produced more fixations on empty squares than did intermediates. When fixating pieces, experts produced a greater proportion of fixations on relevant pieces than did intermediates. It is argued that expert chess players perceptually encode chess configurations, rather than individual pieces, and, consequently, parafoveal or peripheral processing guides their eye movements, producing a pattern of saccadic selectivity by piece saliency.
Avital Deutsch; Ram Frost; Alexander Pollatsek; Keith Rayner
In: Language and Cognitive Processes, vol. 15, no. 4-5, pp. 487–506, 2000.
Hebrew words are composed of two interwoven morphemes: a triconso- nantal root and a word pattern. Two experiments examined the effect of the root morpheme on word identi?cation by assessing parafoveal preview bene?t effects.Although the information of the previewwas not consciously perceived, preview of the root's letters facilitated both naming and lexical decisions of target words derived from these roots. These results converge with previous results in Hebrew using the masked priming paradigm, suggesting that morphological units mediate early stages of word identification in Hebrew.
D. W. J. Cabel; I. T. Armstrong; Eyal M. Reingold; D. P. Munoz
In: Experimental Brain Research, vol. 133, no. 4, pp. 431–441, 2000.
We examined inhibitory control in an oculomotor countermanding task, where the primary task required a saccadic eye movement be made to a target and a less-frequent secondary task required that the movement be halted. Previous studies have used a visual stimulus presented centrally on the fovea as the signal to stop or countermand a saccade. In these previous studies, there are at least two possible sources of saccadic inhibition: (1) sensory stimulation at the fovea can elicit a bottom-up mechanism, where a visual transient signal can delay or inhibit the developing saccade command; and (2) information based on the task instruction can be used to initiate a top-down mechanism to halt the movement. In the present study, we used both visual and auditory stop signals to test the hypothesis that the bottom-up mechanism is activated only after presentation of a foveal visual stop signal. Subjects were instructed first to look at a central spot and then to look to an eccentric visual target that appeared randomly to the left or right of center. On about one-third of the trials, a stop signal was presented. Three types of stop signals were used with equal probability: a broad-band noise burst (auditory), a central fixation spot (visual), and a combination of the auditory and visual stimuli (combined). Saccadic reaction time and stop-signal accuracy were used to calculate stop signal reaction time (SSRT), an estimate of the time required to inhibit the eye movement. Mean SSRT was longer for the auditory stop signals (201 ms) than for the signals with a foveal visual component (visual 113 ms; combined 91 ms). We conclude that a foveal visual stop signal in an oculomotor countermanding task changes the measure of inhibitory control to reflect not only inhibitory processes but also the sensory information afforded by stimulation at the fovea.
John Schlag; Rick H. Cai; Andrews Dorfman; Ali Mohempour; Madeleine Schlag-Rey
Extrapolating movement without retinal motion Journal Article
In: Nature, vol. 403, pp. 38–39, 2000.
In contrast to the perception of a stationary object that is briefly flashed in the dark, a continuously visible moving object is seen as being ahead of its actual position at the time of the flash. An explanation for this simple effect, in which a stimulus moving on the retina is seen as being further along its path and not where it was in space when its signal impinged on the retina, is keenly debated. We show here that this illusion is not just limited to retinal motion, and that perceptual mislocalization occurs even when stimulus motion is inferred entirely from extra-retinal information, for example by movement of the observer's head or whole body, without retinal motion. The phenomenon may therefore rely on a much more general mechanism.
William C. Schmidt
Endogenous attention and illusory line motion reexamined Journal Article
In: Journal of Experimental Psychology: Human Perception and Performance, vol. 26, no. 3, pp. 980–996, 2000.
P. Downing and A. Treisman's (1997) failure to replicate an effect of endogenous attention on the direction of illusory line motion (ILM) was reexamined. Four experiments with slightly modified stimulus presentation methods based on gradient theories of ILM found that endogenous attention directed to 1 of 2 similar priming objects is capable of influencing experienced motion direction within a subsequently presented line. The endogenous effect on ILM was consistent with a concomitant response-time discrimination task, was robust across naive and informed participants, occurred whether eye fixation was monitored or not, and occurred under conditions where multiple motion response categories were available to participants. The endogenous effect disappeared when participants moved their eyes to the attended item, when there was no motivation to endogenously attend, and when the presentation methods of P. Downing and A. Treisman (1997) were used.
Jiye Shen; Eyal M. Reingold; Marc Pomplun
In: Perception, vol. 29, no. 2, pp. 241–250, 2000.
We examined the flexibility of guidance in a conjunctive search task by manipulating the ratios between different types of distractors. Participants were asked to decide whether a target was present or absent among distractors sharing either colour or shape. Results indicated a strong effect of distractor ratio on search performance. Shorter latency to move, faster manual response, and fewer fixations per trial were observed at extreme distractor ratios. The distribution of saccadic endpoints also varied flexibly as a function of distractor ratio. When there were very few same-colour distractors, the saccadic selectivity was biased towards the colour dimension. In contrast, when most of the distractors shared colour with the target, the saccadic selectivity was biased towards the shape dimension. Results are discussed within the framework of the guided search model.
Eli Brenner; Frans W. Cornelissen
In: Vision Research, vol. 40, no. 19, pp. 2557–2563, 2000.
It is well established that all kinds of visual attributes are processed separately within the brain. This separation is related to differences in the information that is relevant for the different attributes. When attributes differ greatly (such as colour and motion) it is obvious that they must rely on different information. However, separating the processing of different attributes could also allow highly related attributes to evolve independently, so that they end up being judged on the basis of different types of information. Here, we examine the case of egocentric and relative localisation. For judging egocentric positions, the orientation of the eyes has to be taken into account. This is not so for judging relative positions. We demonstrate that these two attributes can be processed separately by showing that simultaneous judgements of relative and egocentric position differ in their dependency on eye orientation. Subjects pursued a moving dot. We flashed either single targets, or pairs of targets with a 67 ms interval between them, directly below the subjects' gaze. As the eyes were moving during the 67 ms interval, the retinal separation between pairs of targets was different from their actual separation. Subjects indicated the position at which they saw the targets with reasonable reproducibility, with a consistent bias in the direction of the eye movement. However, when two targets were flashed, the indicated separation between them usually coincided with their retinal separation, rather than with their actual separation. We conclude that egocentric and relative spatial positions can be estimated separately and simultaneously, on the basis of different types of information.
Raymond Bertram; Jukka Hyönä; Matti Laine
In: Language and Cognitive Processes, vol. 15, no. 4/5, pp. 367–388, 2000.
This paper is concernedwith the role of context on the processing of in?ected nouns inFinnish. Identi?cation of partitive plurals with the homonymic suf?x -jA was studied by presenting the target nouns in a sentence context and by recording durations of readers' eye ?xations and self-paced reading times for these targets. A recent visual lexical decision study indicated that the same in?ected words with -jA were sensitive to surface frequency manipulations, but not to base frequency manipulations. The authors interpreted these results to suggest that these in?ectional forms are stored and processed by means of their whole-word representations. In contrast, the present context study shows both a surface frequency effect and a lagged base frequency effect. We argue that syntactic cues prior to the target word prime the in?ectional reading of the -jA suf?x, and as a consequence the base is reinstated as an effective unit in processing these nouns with a homonymic suf?x. INTRODUCTION
Josef N. Geest; Maarten A. Frens
In: Vision Research, vol. 114, pp. 185–195, 2000.
A video-based 2D eye-tracking system (EyeLink version 2.04, SR Research Ltd/SMI) was compared with the scleral search coil technique for its performance on recording the properties of fixations and saccadic eye movements. Fixation positions and saccadic properties (amplitude, duration, and peak velocity) were calculated independently from the data of the two systems that recorded eye positions simultaneously. Fixation positions were well correlated between the video and the coil output with an average discrepancy of B 1° over a tested range of 40 by 40° of visual angle. With respect to the saccade analysis, the values measured by the video system were fitted as a linear function of the values measured by the coil system. Highly correlated linear fits with slopes near one were obtained for all the saccadic parameters. Main sequence relationships (amplitudes– duration and amplitude–peak velocity) were also similar for both systems. A disadvantage of the video method is its low sample rate of 250 Hz. The relatively noisier estimate of all parameters of small saccades could be attributed to this low sampling frequency.
Timothy L. Hodgson; Adnan Bajwa; Adrian M. Owen; Christopher Kennard
In: Journal of Cognitive Neuroscience, vol. 12, no. 5, pp. 894–907, 2000.
In this paper, we describe a novel approach to the study of problem solving involving the detailed analysis of natural scanning eye movements during the "one-touch" Tower-of-London (TOL) task. We showed subjects a series of pictures depicting two arrangements of colored balls in pockets within the upper and lower halves of a computer display. The task was to plan (but not to execute) the shortest movement sequence required to rearrange the balls in one half of the display (the Workspace) to match the arrangement in the opposite half (the Goalspace) and indicate the minimum number of moves required for problem solution. We report that subjects are more likely to look towards the Goalspace in the initial period after picture presentation, but bias gaze towards the Workspace during the middle of trials. Towards the end of a trial, subjects are once again more likely to fixate the Goalspace. This pattern is found regardless of whether the subjects solve problems by rearranging the balls in the lower or upper visual fields, demonstrating that this strategy correlates with discrete phases in problem solving. A second experiment showed that efficient planners direct their gaze selectively towards the problem critical balls in the Workspace. In contrast, individuals who make errors spend more time looking at irrelevant items and are strongly influenced by the movement strategy needed to solve the preceding problem. We conclude that efficient solution of the TOL requires the capacity to generate and flexibly shift between control sets, including those underlying ocular scanning. The role of working memory and the prefrontal cerebral cortex in the task are discussed.
David E. Irwin; Angela M. Colcombe; Arthur F. Kramer; Sowon Hahn
In: Vision Research, vol. 40, no. 10-12, pp. 1443–1458, 2000.
In three experiments we investigated whether attentional and oculomotor capture occur only when object-defining abrupt onsets are used as distractors in a visual search task, or whether other salient stimuli also capture attention and the eyes even when they do not constitute new objects. The results showed that abrupt onsets (new objects) are especially effective in capturing attention and the eyes, but that luminance increments that do not accompany the appearance of new objects capture attention as well. Color singletons do not capture attention unless subjects have experienced the color singleton as a search target in a previous experimental session. Both abrupt onsets and luminance increments elicit reflexive, involuntary saccades whereas transient color changes do not. Implications for theories of attentional capture are discussed.
Laurence R. Harris; Andrew T. Smith
In: Experimental Brain Research, vol. 130, no. 1, pp. 67–72, 2000.
A previous study has suggested that second-order motion is ineffective at driving optokinetic nystagmus (OKN) when presented alone. First- and second-order motion cues interact in creating the perception of motion. Is there an interaction between first- and second-order cues in the control of eye movements? We presented combinations of first- and second-order cues moving in the same or opposite directions and measured the eye movements evoked, to look for a modification of the oculomotor response to first-order motion by simultaneously presented second-order cues. Dynamic random noise was used as a carrier for first- and second-order drifting gratings (13.4 degrees/s; 0.25 cycles/degree; 64 x 48 degrees screen viewed at 28.5 cm). Second-order gratings were defined by spatial modulation of the luminance flicker frequency of noise pixels of constant contrast (50%). A first-order, luminance-defined grating (13.4 degrees/s; 0.25 cycles/degree; variable contrast from 4-50%) was moved in either the same or the opposite direction. Eye movements were recorded by video-oculography from six subjects as they looked straight ahead. The gain (eye velocity/stimulus velocity) of first-order-evoked OKN increased with contrast. The presence of flicker-defined second-order motion in the opposite direction attenuated this OKN below a first-order contrast of 15%, although it had little effect at higher contrasts. When first- and second-order motion were in the same direction, there was an enhancement of the OKN response. We conclude that second-order motion can modify the optokinetic response to simultaneously presented first-order motion.
Gillian A. OʼDriscoll; Anne-Lise V. G. Wolff; Chawki Benkelfat; Patrik S. Florencio; Samarthji Lal; Alan C. Evans
In: NeuroReport, vol. 11, no. 6, pp. 1335–1340, 2000.
We used PET to study differences in cerebral blood flow (CBF) in smooth pursuit, predictive saccades and fixation. Eye movements were monitored in the scanner. Compared with fixation, pursuit and predictive saccades activated a network of highly similar areas, including frontal eye fields, supplementary eye fields, V5 and medial cuneus. Our findings are consistent with non-human primate studies that suggest that pursuit and saccades are controlled by similar and adjacent neural areas. Pursuit was associated with greater activation of caudate than saccades, suggesting a role for basal ganglia in pursuit that is consistent with studies of neurological populations. Saccades were associated with greater activation of cerebellum and frontal eye fields. A frontal-cerebellar loop may be important in coordinating the preparation and timing of saccades in predictive tracking.
Alexander Pollatsek; Jukka Hyönä; Raymond Bertram
In: Journal of Experimental Psychology: Human Perception and Performance, vol. 26, no. 2, pp. 820–833, 2000.
The processing of transparent Finnish compound words was investigated in 2 experiments in which eye movements were recorded while sentences were read silently. The frequency of the second constituent had a large influence (95 ms) on gaze duration on the target words, but its influence was relatively late in processing: A clear effect only occurred on the probability of a third fixation. The frequency of the whole compound word had a similar influence on gaze duration (82 ms) and influenced eye movements at least as rapidly as did the frequency of the second constituent. These results, together with an earlier finding that the frequency of the first constituent affected the first fixation duration, indicate that the identification of these compound words involves parallel processing of both morphological constituents and whole-word representations.
Arthur F. Kramer; Sowon Hahn; David E. Irwin; Jan Theeuwes
Previous research has shown that during visual search young and old adults' eye movements are equivalently influenced by the appearance of task-irrelevant abrupt onsets. The finding of age-equivalent oculomotor capture is quite surprising in light of the abundant research suggesting that older adults exhibit poorer inhibitory control than young adults on a variety of different tasks. In the present study, we examined the hypothesis that oculomotor capture is age invariant when subjects' awareness of the appearance of task-irrelevant onsets is low, but that older adults will have more difficulty than young adults in inhibiting reflexive eye movements to task-irrelevant onsets when awareness of these objects is high. Our results were consistent with the level-of-awareness hypothesis. Young and old adults showed equivalent patterns of oculomotor capture with equiluminant onsets, but older adults misdirected their eyes to bright onsets more often than young adults did.
Alexander P. Leff; Sophie K. Scott; H. Crewes; Timothy L. Hodgson; A. Cowey; D. Howard; Richard J. S. Wise
Impaired reading in patients with right hemianopia Journal Article
In: Annals of Neurology, vol. 47, no. 2, pp. 171–178, 2000.
A left occipital stroke may result in alexia for two reasons, which may coexist depending on the distribution of the lesion. A lesion of the left lateroventral prestriate cortex or its afferents impairs word recognition ("pure" alexia). If the left primary visual cortex or its afferents are destroyed, resulting in a complete right homonymous hemianopia, rightward saccades during text reading are disrupted ("hemianopic" alexia). By using functional imaging, we showed two separate but interdependent systems involved in reading. The first, subserving word recognition, involved the representation of foveal vision in the left and right primary visual cortex and the ventral prestriate cortex. The second system, responsible for the planning and execution of reading saccades, consisted of the representation of right parafoveal vision in the left visual cortex, the bilateral posterior parietal cortex (left > right), and the frontal eye fields (right > left). Disruption of this distributed neural system was demonstrated in patients with severe right homonymous hemianopia, commensurate with their inability to perform normal reading eye movements. Text reading, before processes involved in comprehension, requires the integration of perceptual and motor processes. We have demonstrated these distributed neural systems in normal readers and have shown how a right homonymous hemianopia disrupts the motor preparation of reading saccades during text reading.
Chiang-Shan Ray Li; Mon-Chu Chen; Yong-Yi Yang; Hsueh-Ling Chang; Chia-Yih Liu; Seng Shen; Ching-Yen Chen
In: Behavioural Brain Research, vol. 111, no. 1-2, pp. 61–69, 2000.
Mounting evidence suggests that obsessive compulsive disorder (OCD) results from functional aberrations of the fronto-striatal circuitry. However, empirical studies of the behavioral manifestations of OCD have been relatively lacking. The present study employs a behavioral task that allows a quantitative measure of how alternative percepts are formed from one moment to another, a process mimicking the brain state in which different thoughts and imageries compete for access to awareness. Eighteen patients with OCD, 12 with generalized anxiety disorder, and 18 normal subjects participated in the experiment, in which they viewed one of the three Schroder staircases and responded by pressing a key to each perceptual reversal. The results demonstrate that the patients with OCD have a higher perceptual alternation rate than the normal controls. Moreover, the frequency of perceptual alternation is significantly correlated with the Yale-Brown obsessive compulsive and the Hamilton anxiety scores. The increase in the frequency of perceptual reversals cannot easily be accounted for by learning or by different patterns of eye fixations on the task. These results provide further evidence that an impairment of the inhibitory function of the cortico-striatal circuitry might underlie the etiology of OCD. The implications of the results for a general role of the cortico-striatal circuitry in mediating awareness are discussed.
Sebastiaan F. W. Neggers; Harold Bekkering
In: Journal of neurophysiology, vol. 83, no. 2, pp. 639–651, 2000.
It is well known that, typically, saccadic eye movements precede goal-directed hand movements to a visual target stimulus. Also pointing in general is more accurate when the pointing target is gazed at. In this study, it is hypothesized that saccades are not only preceding pointing but that gaze also is stabilized during pointing in humans. Subjects, whose eye and pointing movements were recorded, had to make a hand movement and a saccade to a first target. At arm movement peak velocity, when the eyes are usually already fixating the first target, a new target appeared, and subjects had to make a saccade toward it (dynamical trial type). In the statical trial type, a new target was offered when pointing was just completed. In a control experiment, a sequence of two saccades had to be made, with two different interstimulus intervals (ISI), comparable with the ISIs found in the first experiment for dynamic and static trial types. In a third experiment, ocular fixation position and pointing target were dissociated, subjects pointed at not fixated targets. The results showed that latencies of saccades toward the second target were on average 155 ms longer in the dynamic trial types, compared with the static trial types. Saccades evoked during pointing appeared to be delayed with approximately the remaining deceleration time of the pointing movement, resulting in "normal" residual saccadic reaction times (RTs), measured from pointing movement offset to saccade movement onset. In the control experiment, the latency of the second saccade was on average only 29 ms larger when the two targets appeared with a short ISI compared with trials with long ISIs. Therefore the saccadic refractory period cannot be responsible for the substantially bigger delays that were found in the first experiment. The observed saccadic delay during pointing is modulated by the distance between ocular fixation position and pointing target. The largest delays were found when the targets coincided, the smallest delays when they were dissociated. In sum, our results provide evidence for an active saccadic inhibition process, presumably to keep steady ocular fixation at a pointing target and its surroundings. Possible neurophysiological substrates that might underlie the reported phenomena are discussed.
Antje S. Meyer; Femke Meulen
In: Psychonomic Bulletin & Review, vol. 7, no. 2, pp. 314–319, 2000.
An earlier experiment (Meyer, Sleiderink, & Levelt, 1998) had shown that speakers naming object pairs usually inspected the objects in the required order of mention (left object first) and that the viewing time for the left object depended on the word frequency of its name. In the present experiment, object pairs were presented simultaneously with auditory distractor words that could be phonologically related or unrelated to the name of the object to be named first. The speech onset latencies and the viewing times for that object were shorter after related distractors than after unrelated distractors. Since this phonological priming effect, like the word frequency effect, most likely arises during word-form retrieval, we conclude that the shift of gaze from the first to the second object is initiated after the word form of the first object's name has been accessed.
Diane C. Gooding; Jeffrey A. Grabowski; Christian S. Hendershot
In: Psychiatry Research, vol. 97, no. 2-3, pp. 119–128, 2000.
A few investigators have suggested that visual fixation abnormalities may serve as an endophenotype of liability for schizophrenia. However, the data are equivocal. Conflicting reports regarding the specificity of fixation deficits to schizophrenia may be attributable to methodological differences. Thirty-four schizophrenia patients, 20 bipolar patients, and 30 non-patient controls were presented targets for central fixation. Fixation was scored in terms of frequency of saccades as well as qualitative ratings. Analysis of variance on the number of saccades produced during fixation revealed that the three groups did not differ. Similarly, we observed that the schizophrenia patients did not differ from either bipolar patients or controls in terms of ratings of fixation quality. It appears that schizophrenia patients are not characterized by poor visual fixation. The findings are discussed in terms of the viability of visual fixation as a marker of schizophrenic diathesis, as well as possible implications for the analysis of schizophrenia patients' visual search performance.
Diane C. Gooding; Meghan D. Miller; Thomas R. Kwapil
In: Psychiatry Research, vol. 93, no. 1, pp. 41–54, 2000.
Subjects identified by Perceptual Aberration-Magical Ideation (Per-Mag) scores (n = 97), Social Anhedonia (SocAnh) scores (n = 45), and Physical Anhedonia (PhysAnh) scores (n = 31) as well as normal controls (n = 94), underwent psychophysiological and clinical assessment. This is the first published investigation of pursuit system functioning in three groups of questionnaire-identified at-risk individuals. Pursuit during a simple non- monitor tracking task was measured using root-mean-square error (RMSE) scores and pursuit gain scores. Fixation performance was measured in terms of number of saccades away from the central fixation point. The at-risk subjects were more likely to display aberrant smooth pursuit tracking than controls, though there were no significant differences between the at-risk subjects endorsing items relevant to positive-symptom schizotypy and those endorsing items pertaining to negative-symptom schizotypy. The groups did not differ significantly in their visual fixation performance. Participants were also evaluated for the presence of Axis I symptomatology and psychotic-like experiences. Neither the experimental subjects nor the control subjects displayed a significant association between ocular motor performance and psychotic-like experiences. These findings are consistent with prior evidence that pursuit tracking is a trait characteristic, independent of clinical status.
Zenzi M. Griffin; Kathryn Bock
What the eyes say about speaking Journal Article
In: Psychological Science, vol. 11, no. 4, pp. 274–279, 2000.
To study the time course of sentence formulation, we monitored the eye movements of speakers as they described simple events. The similarity between speakers' initial eye movements and those ofobservers performing a nonverbal event-comprehension task suggested that response-relevant information was rapidly extracted from scenes, allowing speakers to select grammatical subjects based on comprehended events rather than salience. When speaking extem- poraneously, speakers began fixating pictured elements less than a second before naming them within their descriptions, a finding con- sistent with incremental lexical encoding. Eye movements anticipated the order of mention despite changes in picture orientation, in who- did-what-to-whom, and in sentence structure. The results support Wundt's theory of sentence production. From
Kalanit Grill-Spector; Tammar Kushnir; Talma Hendler; Rafael Malach
In: Nature Neuroscience, vol. 3, no. 8, pp. 837–893, 2000.
To investigate the relationship between perceptual awareness and brain activity, we measured both recogni-tion performance and fMRI signal from object-related areas in human cortex while images were presented briefly using a masking protocol. Our results suggest that recognition performance is correlated with selective activation in object areas. Selective activation was correlated to object naming when exposure duration was varied from 20 to 500 milliseconds. Subjects' recognition during identical visual stimulation could be enhanced by training, which also increased the fMRI signal. Overall, the correlation between recognition per- formance and fMRI signal was highest in occipitotemporal object areas (the lateral occipital complex).
Iain D. Gilchrist; Monika Harvey
Refixation frequency and memory mechanisms in visual search Journal Article
In: Current Biology, vol. 10, no. 19, pp. 1209–1212, 2000.
Visual search - looking for a target object in the presence of a number of distractor items - is an everyday activity for humans (for example, finding the car in a busy car park) and animals (for example, foraging for food). Our understanding of visual search has been enriched by an interdisciplinary effort using a wide range of research techniques including behavioural studies in humans , single-cell electrophysiology , transcranial magnetic stimulation , event-related potentials  and studies of patients with focal brain injury . A central question is what kind of information controls the search process. Visual search is typically accompanied by a series of eye movements, and investigating the nature and location of fixations helps to identify the kind of information that might control the search process. It has already been demonstrated that objects are fixated if they are visually similar to the target . Also, if an item has been fixated, it is less likely to be returned to on the subsequent saccade. This automatic process is referred to as inhibition of return (IOR [7,8]). Here, we investigated the role of memory for which items had been fixated previously. We found that, during search, subjects often refixated items that had been previously fixated. Although there were fewer return saccades than would be expected by chance, the number of refixations indicated limited functional memory, indeed the memory effects that were present may primarily be a result of IOR.
Diane C. Gooding
In: Schizophrenia Research, vol. 35, no. 2, pp. 157–166, 1999.
Individuals who scored high on Perceptual Aberration-Magical Ideation Scales (Per-Mag; n = 90), the Social Anhedonia Scale (SocAnh; n = 39), and control participants (n = 89) were administered saccadic refixation (prosaccade) and saccadic suppression (antisaccade) tasks. Eye movements were scored in terms of error rates and latency. None of the groups differed in terms of their performance on the prosaccade task. Both the Per-Mag (p < 0.01) and SocAnh (p < 0.05) groups exceeded the controls in terms of mean antisaccade errors. The high-risk groups did not differ from each other. Eighteen of the Per-Mag individuals and 10 of the SocAnh individuals displayed deviant antisaccade performance. These findings are particularly interesting in light of suggestive evidence that antisaccade task deficits may serve as a marker of susceptibility to schizophrenia. It is hypothesized that the individuals who scored aberrantly on the Chapman scales and displayed antisaccade performance deficits are most likely to be at risk for the development of psychosis.
Frans W. Cornelissen; John J. Dobbelsteen
Heading detection with simulated visual field defects Journal Article
In: Visual Impairment Research, vol. 1, no. 2, pp. 71–84, 1999.
We examined how simulated visual field defects influence performance on a heading task to gain insight into the origins of the poorer performance seen in subjects with real visual field defects. We simulated tunnel vision and a central scotoma during ego-translation. Real-time gaze position was used to generate the appropriate optic flow pattern on the screen. The subjects' task was to direct their gaze at the continuously changing direction of heading. Limiting the peripheral view, as in tunnel vision, or introducing a central scotoma, as in macular degeneration, affected both the accuracy with which subjects could estimate heading direction as well as the time it took them to do this. Under natural circumstances, optic flow patterns can change both smoothly, such as during pursuit of an object, and more abruptly, such as when making saccades. Therefore, we examined performance during both of these types of change. While accuracy was the same under these conditions, processing time was differentially affected. When limiting peripheral view, the influence of the field defect on processing time was larger when the heading changed abruptly than when it changed smoothly. The reverse was the case for simulated central scotomas. The influence of the defect on processing time was largest when the head- ing changed smoothly. Our results further point out that the calculations underlying heading detection can be performed very quickly, with processing time strongly dependent upon the speed of the simulated translation and the size of the stimulated visual area.
Avital Deutsch; Keith Rayner
Initial fixation location effects in reading Hebrew words Journal Article
In: Language and Cognitive Processes, vol. 14, no. 4, pp. 393–421, 1999.
Three experiments examined initial fixation position effects for Hebrew readers. In English, the preferred viewing location (where readers' eyes initially land in a word) is to the left of the centre of words, and words presented in isolation are identified more easily when the initial fixation point is near the optimal viewing location (close to the centre of the word). In Experiment 1, we found that the preferred viewing location for Hebrew readers was to the right of the centre of words and that it was notmodulated by infectional morphological constraints. However, the results from the word identification task in Experiments 2 and 3 indicated that derivational morphological constraints do modulate the optimal viewing location.
Gerry T. M. Altmann; Yuki Kamide
In: Cognition, vol. 73, no. 3, pp. 247–264, 1999.
Participants' eye movements were recorded as they inspected a semi-realistic visual scene showing a boy, a cake, and various distractor objects. Whilst viewing this scene, they heard sentences such as 'the boy will move the cake' or 'the boy will eat the cake'. The cake was the only edible object portrayed in the scene. In each of two experiments, the onset of saccadic eye movements to the target object (the cake) was significantly later in the move condition than in the eat condition; saccades to the target were launched after the onset of the spoken word cake in the move condition, but before its onset in the eat condition. The results suggest that information at the verb can be used to restrict the domain within the context to which subsequent reference will be made by the (as yet unencountered) post-verbal grammatical object. The data support a hypothesis in which sentence processing is driven by the predictive relationships between verbs, their syntactic arguments, and the real-world contexts in which they occur.
Kin Fai Ellick Wong; Hsuan-Chih Chen
In: Language and Cognitive Processes, vol. 14, no. 5-6, pp. 461–480, 1999.
The use of orthographic and phonologic information in reading Chinese text was investigated using an eye-monitoring technique. The basic manipulation was to change a critical character in a short passage so that various combinations of orthographic and phonological information were altered. Patterns of disruption caused by different manipulations were compared in order to reveal the use of orthographic and phonological information from individual characters during reading for comprehension. Results showed that orthographic manipulations produced reliable and early disruption in first fixation duration at the target word position. In contrast, phonological effects were only found in the measure of a relatively late stage of processing (i.e., total reading time) at the target position, but not in early measures of processing. These results supported the position that it is orthography rather than phonology, which plays an early and dominant role in reading Chinese.
Jan Theeuwes; Arthur F. Kramer; Sowon Hahn; David E. Irwin; Gregory J. Zelinsky
Influence of attentional capture on oculomotor control Journal Article
In: Journal of Experimental Psychology: Human Perception and Performance, vol. 25, no. 6, pp. 1595–1608, 1999.
Previous research has shown that when searching for a color singleton, top-down control cannot prevent attentional capture by an abrupt visual onset. The present research addressed whether a task-irrelevant abrupt onset would affect eye movement behavior when searching for a color singleton. Results show that in many instances the eye moved in the direction of the task-irrelevant abrupt onset. There was evidence that top-down control could neither entirely prevent attentional capture by visual onsets nor prevent the eye from starting to move in the direction of the onset. Results suggest parallel programming of 2 saccades: 1 voluntary goal-directed eye movement toward the color singleton target and 1 stimulus-driven eye movement reflexively elicited by the abrupt onset. A neurophysiologically plausible model that can account for the current findings is discussed.
Sebastiaan F. W. Neggers; H. Bekkering
In: Experimental Brain Research, vol. 125, no. 1, pp. 97–107, 1999.
In this study, we compared separate and coordinated eye and hand movements towards visual or somatosensory target stimuli in a dark room, where no visual position information about the hand could be obtained. Experiment 1 showed that saccadic reaction times (RTs) were longer when directed to somatosensory targets than when directed to visual targets in both single- and dual-task conditions. However, for hand movements, this pattern was only found in the dual-task condition and not in the single-task condition. Experiment 1 also showed that correlations between saccadic and hand RTs were significantly higher when directed towards somatosensory targets than when directed towards visual targets. Importantly, experiment 2 indicated that this was not caused by differences in processing times at a perceptual level. Furthermore, hand-pointing accuracy was found to be higher when subjects had to move their eyes as well (dual task) compared to a single-task hand movement. However, this effect was more pronounced for movements to visual targets than to somatosensory targets. A schematic model of sensorimotor transformations for saccadic eye and goal-directed hand movements is proposed and possible shared mechanisms of the two motor systems are discussed.
Gillian A. O'Driscoll; Chawki Benkelfat; Patrik S. Florencio; Anne-Lise V. G. Wolff; Ridha Joober; Samarthji Lal; Alan C. Evans
In: Archives of General Psychiatry, vol. 56, no. 12, pp. 1127–1134, 1999.
BACKGROUND: Schizophrenia is thought to arise from the interaction of genetically mediated and environmentally triggered abnormalities in brain function. Reduced frontal activation, reported in schizophrenic patients, may be one expression of genetic risk. The present study investigated whether frontal activation in relatives of schizophrenic patients would be related to eye tracking deficits (ETD), which are considered a behavioral marker of risk for schizophrenia. METHODS: Subjects were first-degree relatives of schizophrenic patients (n = 17) and controls (n = 11). Relatives were divided into those with normal and abnormal pursuit based on qualitative ratings. Subjects were scanned using positron emission tomography and the H(2)15O bolus subtraction technique while performing smooth pursuit and fixation. Brain areas more active in pursuit than fixation were identified in the 3 groups. Correlations were used to investigate the relationship between activation of pursuit regions and pursuit gain in the relatives. RESULTS: Controls significantly activated frontal eye fields (FEFs) and posterior areas, including the motion processing area, V5, and cuneus. The 2 groups of relatives activated the same posterior regions as controls, but differed from each other in activation of FEFs. Relatives with normal tracking activated right dorsal FEFs while relatives with ETD did not. Individual subtractions revealed that 90% of controls and 100% of the relatives with normal tracking activated FEFs during pursuit compared with 42% of relatives with ETD (P = .009). Pursuit gain was significantly and selectively associated with percent activation of right dorsal FEFs (r = 0.74). CONCLUSIONS: Subtle frontal dysfunction seems to be a pathophysiological substrate of ETD in relatives of schizophrenic patients, and may be one aspect of genetically mediated differences in brain function relevant to schizophrenia
T. Niemann; Markus Lappe; A. Büscher; Klaus-Peter Hoffmann
In: Vision Research, vol. 39, no. 7, pp. 1359–1371, 1999.
Self-movement in a structured environment induces retinal image motion called optic flow. Optic flow on one hand provides information about the direction of self-motion. On the other hand optic flow presents large field visual motion which will elicit eye movements for the purpose of image stabilization. We investigated oculomotor behavior in humans during the presentation of radial optic flow fields which simulated forward or backward self-motion. Different conditions and oculomotor tasks were compared. In one condition, subjects had to actively pursue single dots in a radial flow pattern. In a second condition, subjects had to pursue single dots over a dark background. These dots accelerated or decelerated similar to single dots in radial optic flow. In a third condition, subjects were asked to passively view the entire optic flow stimulus. Smooth pursuit eye movements with high gain were observed when dots were actively pursued. This was true for single dots moving over a homogeneous background and for single dots in the optic flow. Passive viewing of optic flow stimuli evoked eye movements that resembled an optokinetic nystagmus. Slow phase eye movements tracked the motion of elements in the optic flow. Gain was low for simulated forward self-motion (expanding optic flow) and high for simulated backward movement self-motion (contracting optic flow). Thus, voluntary pursuit and passive optokinetic responses yielded different gain for the tracking of elements of an expanding optic flow pattern. During passive viewing of the optic flow stimulus, gaze was usually at or near the focus of radial flow. Our results give insights into the oculomotor performances and needs for image stabilization during self-motion and in the role of gaze strategy for the detection of the direction of heading.
Raymond M. Klein; W. Joseph Macinnes
Inhibition of return is a foraging facilitator in visual search Journal Article
In: Psychological Science, vol. 10, no. 4, pp. 346–352, 1999.
Using overt orienting, participants searched a complex visual scene for a camouflaged target (Waldo from the “Where's Waldo? ™ ” books). After several saccades, we presented an uncamou- flaged probe (black disk) while removing or maintaining the scene, and participants were required to locate this probe by foveating it. Inhibition of return was observed as a relative increase in the time required to locate these probes when they were in the general region of a previous fixation, but only when the search array remained present. Perhaps also reflecting inhibition of return, preprobe saccades showed a strong directional bias away from a previously fixated region. Together with recent studies that replicate the finding of inhibition at distractor locations following serial but not parallel visual search—so long as the search array remains visible—these data strongly support the proposal that inhibition of return functions to facilitate visual search by inhibiting orienting to previously examined locations.
Arthur F. Kramer; Sowon Hahn; David E. Irwin; Jan Theeuwes
In: Psychology and Aging, vol. 14, no. 1, pp. 135–154, 1999.
Two studies examined potential age-related differences in attentional capture. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. On half the trials, a new stimulus (i.e., a sudden onset) appeared simultaneously with the presentation of the color singleton target. The onset was always a task-irrelevant distractor. Response times were lengthened, for both young and old adults, whenever an onset distractor appeared, despite the fact that subjects reported being unaware of the appearance of the abrupt onset. Eye scan strategies were also disrupted by the appearance of the onset distractors. On about 40% of the trials on which an onset appeared, subjects made an eye movement to the task-irrelevant onset before moving their eyes to the target. Fixations close to the onset were brief, suggesting parallel programming of a reflexive eye movement to the onset and goal-directed eye movement to the target. Results are discussed in terms of age-related sparing of the attentional and oculomotor processes that underlie attentional capture.
Jan Theeuwes; Arthur F. Kramer; Sowon Hahn; David E. Irwin
In: Psychological Science, vol. 9, no. 5, pp. 379–385, 1998.
Observers make rapid eye movements to examine the world around them. Before an eye movement is made, attention is covertly shifted to the location of the object of interest. The eyes typically will land at the position at which attention is directed. Here we report that a goal-directed eye movement toward a uniquely colored object is disrupted by the appearance of a new but task-irrelevant object, unless subjects have a sufficient amount of time to focus their attention on the location of the target prior to the appearance of the new object. In many instances, the eyes started moving toward the new object before gaze started to shift to the color-singleton target. The eyes often landed for a very short period of time (25–150 ms) near the new object. The results suggest parallel programming of two saccades: one voluntary, goal-directed eye movement toward the color-singleton target and one stimulus-driven eye movement reflexively elicited by the appearance of the new object. Neuroanatomical structures responsible for parallel programming of saccades are discussed.
Jukka Hyönä; Alexander Pollatsek
In: Journal of Experimental Psychology: Human Perception and Performance, vol. 24, no. 6, pp. 1612–1627, 1998.
The role of morphemic processing in reading was investigated in 2 experiments in which participants read sentences as their eye movements were monitored. The target words were 2-morpheme Finnish compound words. In Experiment 1, the length of the component morphemes was varied and word length was held constant, and in Experiment 2, the uniqueness of the initial morpheme was varied and the rated familiarity and length of the word were held constant. The length of the initial morpheme influenced the location of the second fixation on the target word and the pattern of fixation durations (although it had a negligible influence on the gaze duration of the word). The frequency of the initial morpheme influenced the duration of the first fixation on the target word, had a substantial effect on the gaze duration, and also influenced the location of the first and second fixations on the target word. Subsidiary analyses indicated that these effects were unlikely to stem from orthographic factors such as bigram frequency.
Antje S. Meyer; Astrid M. Sleiderink; Willem J. M. Levelt
In: Cognition, vol. 6, no. 3, pp. B25–B33, 1998.
Eye movements have been shown to reflect word recognition and language comprehension processes occurring during reading and auditory language comprehension. The present study examines whether the eye movements speakers make during object naming similarly reflect speech planning processes. In Experiment 1, speakers named object pairs saying, for instance, ‘scooter and hat'. The objects were presented as ordinary line drawings or with partly deleted contours and had high or low frequency names. Contour type and frequency both significantly affected the mean naming latencies and the mean time spent looking at the objects. The frequency effects disappeared in Experiment 2, in which the participants categorized the objects instead of naming them. This suggests that the frequency effects of Experiment 1 arose during lexical retrieval. We conclude that eye movements during object naming indeed reflect linguistic planning processes and that the speakers' decision to move their eyes from one object to the next is contingent upon the retrieval of the phonological form of the object names.
Diane E. Williams; Eyal M. Reingold; Morris Moscovitch; Marlene Behrmann
In: Canadian Journal of Experimental Psychology, vol. 51, no. 2, pp. 151–164, 1997.
Eye movements were monitored while subjects performed parallel and serial search tasks. In Experiment 1a, subjects searched for an "O" among "X"s (parallel condition) and for a "T" among "L"s (serial condition). In the parallel condition in Experiment 1b, "[symbol: see text]" was the target, and "O"s were distractors; in the serial condition these stimuli switched roles. Displays contained 1, 12, or 24 stimuli, with both target-present and target-absent trials. RT and eye-movement measures (number of fixations, saccadic error, and latency to move) indicated that search efficiency was greatest in the parallel conditions, followed by the serial condition of experiment 1a and, finally, by the serial condition of Experiment 1b. This suggests that eye movements are correlated with the attentional processes underlying visual search.
Dino Chincotta; Jukka Hyönä; Geoffrey Underwood
In: Acta Psychologica, vol. 97, no. 3, pp. 253–275, 1997.
The present study examined whether the reading of language-neutral stimuli, as numerals are, at maximal speed by bilinguals indexes processes related to fluency rather than differences in articulation time between languages. We tested two groups of bilinguals that spoke the same languages (Finnish and Swedish) but whose mother tongues were different and obtained measures of Arabic numeral processing by monitoring eye movements. These measures were contrasted with articulation and numeral reading estimates of word length. The results indicated that Finnish- and Swedish-dominant bilinguals had shorter gaze durations and shorter reading times in their respective dominant languages, whereas both groups articulated digits faster in Swedish than Finnish. The Swedish-dominant group had a larger digit span in Swedish, whereas digit span was marginally greater in Finnish than Swedish for the Finnish-dominant group. The finding that numeral reading was influenced by cognitive loads independent of articulation, thus, moderated the view that bilingual digit span effects are mediated exclusively by variation in word length between languages.