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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.