Visual masking and visual integration across saccadic eye movements.

Studied visual masking and visual integration across saccadic eye movements in 4 experiments. In a 5th experiment, 4 randomly chosen dots from a 3?×?5 dot matrix were presented in 1 fixation, and 4 different dots from the matrix were presented in a 2nd fixation. Ss reported the location of the missing dot. When the 1st display was presented just before the saccade (as in Exps I–III), Ss accurately specified the missing dot location when the dots were presented to the same region of the retina but not when they were presented in the same place in space. When the 1st display was presented well before the saccade (as in Exp IV), Ss performed poorly regardless of retinal or spatial overlap. Results indicate the existence of a short-lived retinotopic visual persistence but provide no support for a spatiotopic visual persistence capable of fusing the contents of successive fixations. It is concluded that transsaccadic integration depends instead on an abstract memory that accumulates position and identity information about the contents of successive fixations. Results are discussed in relation to the work by M. L. Davidson et al (see record 1974-10245-001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stable individual differences across images in human saccadic eye movements.

Individual differences in eye movements during picture viewing were examined across image format, content, and foveal quality in 3 experiments. Experiment 1 demonstrated that an individual's fixation durations were strongly related across 3 types of scene formats and that saccade amplitudes followed the same pattern. In Experiment 2, a similar relationship was observed for fixation durations across faces and scenes, although the amplitude relationship did not hold as strongly. In Experiment 3, the duration and amplitude relationships were observed when foveal information was degraded and even removed. Eye movement characteristics differ across individuals, but there is a great deal of consistency within individuals when viewing different types of images. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Programming saccadic eye movements.

This article addresses questions about the preparatory processes that immediately precede saccadic eye movements. Saccade latencies were measured in a task in which subjects were provided partial advance information about the spatial location of a target fixation. In one experiment, subjects were faster in initiating saccades when they knew either the direction or amplitude of the required movement in advance compared to a condition with equal uncertainty about the number of potential saccade targets but without knowledge of the parameters required to execute the movement. These results suggest that the direction and amplitude for an upcoming saccade were calculated separately, and not in a fixed serial order. In another experiment, subjects appear to have programmed the saccades more holistically—with computations of direction and amplitude parameters occurring simultaneously. The implications of these results for models of eye movement preparation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integrating pictorial information across eye movements.

Six experiments are reported dealing with the types of information integrated across eye movements (EMs) in picture perception. A line drawing of an object was presented in peripheral vision, and the 12 Ss (members of the university community) made an EM to it. During the saccade, the initially presented picture was replaced by another that the S was instructed to name as quickly as possible. The relation between the stimulus on the 1st fixation and the stimulus on the 2nd fixation was varied. Across experiments, there was about 100–230 msec facilitation when the pictures were identical compared with a control condition in which only the target location was specified on the 1st fixation. This finding implies that information about the 1st picture facilitated naming the 2nd picture. When the pictures represented the same concept (e.g., 2 pictures of a horse), there was a 90-msec facilitation effect that could have been the result of either the visual or conceptual similarity of the pictures. However, when the pictures had different names, only visual similarity produced facilitation; there appeared to be inhibition from the competing names. Results of all experiments are consistent with a model in which the activation of both the visual features and the name of the picture seen on the 1st fixation survive the saccade and combine with the information extracted on the 2nd fixation to produce identification and naming of the 2nd picture. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonological codes are used in integrating information across saccades in word identification and reading.

A major issue in reading is the extent to which phonological information is used in visual word perception. The present experiments demonstrated that phonological information acquired on 1 fixation from a word in the parafovea is used to help identify that word when it is later fixated. A homophone of a target word, when presented as a preview in the parafovea, facilitated processing in the target word seen on the next fixation more than a preview of a word matched with the homophone in visual similarity to the target word. This facilitation was observed both in the time to name an isolated target word and in the fixation time on the target word while silently reading a sentence; the preview was virtually never consciously identified in either task. Because the visual similarity of the preview to the target also plays a part in the facilitative effect on the preview, however, codes other than phonological codes are preserved across saccades. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive modification of saccadic eye movements.

Experiments are reported in which the target for a saccadic eye movement was displaced during the saccade. Ss adapted to the displacement by altering the amplitudes of subsequent saccades to compensate for it. Analysis of kinematic details of the saccade trajectories revealed that the adaptation did not arise from a simple remapping of perceived target locations. Instead, the adaptation appeared to be accomplished by a change in the gain of the saccadic system. The gain change arose primarily from a change in the magnitude of the force pulse for the saccade, not a change in the duration of the pulse. These results have implications for the mechanisms that underlie saccades in normal situations. In particular, people can separately adjust the magnitudes and durations of the force pulses used to produce saccades. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of early presemantic phonological code in Chinese character identification.

A backward-masking procedure was used to examine phonological processing in Chinese character identification. In Experiment 1, the character target and mask were presented for 50 ms and 30 ms, respectively. The results indicated graphic but not phonological nor semantic masks affected target recognition. In Experiment 2, the exposure durations of the target and mask were extended to 60 ms and 40 ms, respectively. We observed a significant phonological mask facilitation effect for high-frequency targets and the absence of semantic mask effect. A postexperiment analysis showed that when the high-frequency targets had well-defined meaning, the semantic masks facilitated target identification, whereas when the high-frequency targets had fuzzy meaning, no significant semantic mask effect was obtained. Results indicate that getting at the phonology of high-frequency characters with fuzzy meaning occurs presemantically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activation of phonological codes before access to character meaning in written Chinese.

Two experiments examined whether the speed of activating different aspects of a word's meaning influences the time course of accessing phonology and meaning. The authors used a backward masking paradigm with Chinese materials. When targets were exposed at threshold + 14 ms, homophonic masks were observed to facilitate target identification. Semantic masks in the absence of associative relatedness to targets did not affect recognition, irrespective of target semantic vagueness. Associate masks facilitated the recognition of semantically precise but not vague targets. These findings suggest that phonological activation precedes semantic activation and the activation of associative relatedness of vague-semantic characters. The authors argue that phonological codes are accessed through a character-as-a-whole-to-sound-as-a-whole association. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activation of phonological codes during eye fixations in reading.

Two experiments addressed the issue of whether phonological codes are activated early in a fixation during reading using the fast-priming technique (S. C. Sereno & K. Rayner, 1992). Participants read sentences and, at the beginning of the initial fixation in a target location, a priming letter string was displayed, followed by the target word. Phonological priming was assessed by the difference in the gaze duration on the target word between when the prime was a homophone and when it was a control word equated with the homophone on orthographic similarity to the target. Both experiments demonstrated homophonic priming with prime durations of about 35 ms, but only for high-frequency word primes, indicating that lexicality was guiding the speed of the extraction of phonological codes early in a fixation. Evidence was also obtained for orthographic priming, and the data suggest that orthographic and phonological priming effects interact in a mutually facilitating manner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonological codes and eye movements in reading.

A number of recent studies using eye movement data have yielded evidence suggesting that phonological codes are activated early in an eye fixation. However, experiments reported by M. Daneman and E. Reingold (1993; M. Daneman, E. M. Reingold, & M. Davidson, 1995) yielded data that led them to argue that phonological codes are primarily activated after lexical access has occurred. In this study, 3 experiments were carried out that were conceptually similar to those of M. Daneman and E. Reingold, and the resulting data supported the position that phonological codes are activated very early in an eye fixation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Information integration across eye movements.

The visual world contains more information than can be perceived in a single glance. Consequently, humans make eye and head movements and somehow construct a stable and continuous representation of the visual environment from these successive views. How this is accomplished has puzzled psychologists for over a century. The present research investigated the properties of transsaccadic integration, the integration of information across saccadic eye movements. The results of several experiments suggest that the mental representation of the environment that is constructed across eye movements is surprisingly schematic and undetailed, and based more on the contents of the current fixation than on one's memory for the contents of previous fixations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time course of graphic, phonological, and semantic activation in Chinese character identification.

In reading, lexical form–form relations may be more reliable then form–meaning relations. Accordingly, phonological forms (activated by graphic forms) become actual constituents, rather than addenda, of word identification. These considerations suggest that access to phonological forms can precede meaning access in single-word reading in many circumstances. The time course of form and meaning activation during Chinese word reading was tested in 2 primed-naming experiments varying prime type and prime-target stimulus onset asynchrony (SOA). The results showed a sequence of facilitation over SOA: (a) graphic, (b) phonological, (c) semantic. Words with precise meanings produced more rapid semantic priming than words with vague meanings. Graphic prime facilitation at a 43-ms SOA gave way to inhibition at longer SOAs. The onset of graphic inhibition coincided with the onset of phonological facilitation, suggesting a single identification moment. The authors describe an interactive constituency model that accounts for the pattern of data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of eye and head movements in detecting information about fly balls.

The authors attempted to identify perceptual mechanisms that pick up information for initiating a run to catch fly balls and for judging their landing locations. Fly balls have been shown to be tracked with the eyes and head (R. R. D. Oudejans, C. F. Michaels, F. C. Bakker, & K. Davids, 1999). This raised the question of whether constraining eye and head movements of experienced baseball players by having them wear eye-movement-preventing goggles (eye movements would lead to losing sight of the ball) or a head-movement-preventing neck brace, or both, would limit their capacity (a) to start running in the correct direction and (b) to make correct judgments about the balls' landing locations. Restrictions had minimal effects on response accuracy, but response latency was affected. The goggles increased latency of both running and judging. Moreover, the neck brace decreased judgment time, particularly for difficult balls, suggesting that head stability is important for making judgments. High performance levels suggested that the perceptual system was flexible; that is, different parts of the system can perform the same function. The implications of these findings for perceptual mechanisms are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decrease in saccadic performance after many visually guided saccadic eye movements in monkeys

PURPOSE: To investigate the influence of repeated saccades and of background illumination on the metrics and dynamics of visually guided targeting saccades. METHODS: Eye movements were measured by magnetic search coil technique in seven trained monkeys (Macaca mulatta) while they performed many visually guided saccades in the dark or in dim background light. RESULTS: After 2000 to 7000 saccades in the dark, peak eye velocity on the average decreased by 20%, saccadic gain decreased slightly by 4.5%, and saccadic latency increased by 15%. All parameters also showed increased variability. In contrast, when testing was done in dim light, there was little to no change in average saccadic metrics and latency. CONCLUSIONS: The changes in saccadic metrics and dynamics in the dark do not reflect a change of the ocular plant but may reflect a change in the cortical or cerebellar influences on the brain stem burst generator linked to the monkeys attentional state. Background light mostly prevents this change.     

Perception of everyday visual environments during saccadic eye movements

Subjects were required to execute saccadic eye movements in the horizontal plane which passed through primary gaze. During the saccades, visual images were projected onto a screen which subtended 40 degrees horizontaloy and 26 degrees vertically and was centered on primary gaze. Content, contrast, and intensity of the stimulus patterns and level of illumination of the laboratory background were manipulated to maximise pattern recognition. Little or no detail of the projected images could be discerned under any conditions. Only horizontal laminations were perceived as blurs of appropriate colour. It is concluded that there is no useful perception of the everyday environment during saccades.     

Memory-guided saccadic eye movements: effects of cerebellar disease

We compared the accuracy of oblique, memory-guided saccades if the eye is stationary or moves horizontally during the memory period. We studied 11 patients with cerebellar disease and 11 age-matched control subjects. Normal subjects showed similar accuracy of saccades for both conditions. In contrast, all patients showed greater errors if the eye moved horizontally during the memory period; however, errors of both vertical and horizontal components of memory-guided saccades were similar. Thus, inaccuracy of memory-guided saccades could not be simply attributed to failure to internally monitor change in horizontal gaze during the memory period. Instead, we propose that the greater saccadic errors which occurred when gaze changed during the memory period reflected a disruption of predictive mechanisms governing eye movements.     

Influences of chorion type on saccadic eye movements in twins

PURPOSE: The influence of genetic and prenatal environmental factors on characteristics of saccadic performance were evaluated in young monozygotic (MZ) twins (8-19 years old) of known chorion type. METHODS: Saccadic eye movements were recorded using an infrared system. Saccadic latency, accuracy, and parameters of amplitude-peak velocity exponential equation (main sequence) were quantified. RESULTS: Intraclass correlations of saccadic parameters differed significantly from zero for monochorionic and dichorionic MZ twins. The within-pair mean squares were significantly less, and intraclass correlations were significantly higher in monochorionic than in dichorionic twins for latency and were similar for other saccadic parameters (accuracy, slope of main sequence, and peak velocity for 15 degrees saccades). CONCLUSIONS: These findings confirmed previous reports that saccadic parameters of MZ twins are significantly correlated and indicated that similarity of these parameters seen in MZ twins may be driven both by genetic and by prenatal environmental factors.