Interpersonal coordination tendencies and perception of visual information for decision-making in futsal

This study investigated how futsal players visually perceived information on angular interpersonal coordination relations, between available sources such as nearest defender, goalkeeper position and ball, when deciding to shoot at goal. Experienced players (n = 180) participated in eighteen, video-recorded futsal matches, during which 32 participants wore an eye tracking device. Forty-five sequences of play were selected and edited from the moment a teammate passed the ball to the shooter, until the moment a shot was undertaken. Independent variables included the angle connecting the shooter to their closest defender and goalkeeper, and it’s rate of change (velocity and variability) during performance. Then eye tracking system (TOBII PRO) was used to examine gaze patterns of shooters during task performance. Findings revealed that: (i) futsal players adapted their gaze patterns differently between key information sources when shooting confirmed as: their closest defender, goalkeeper, ball, and court floor; and (ii), the ball was the information source which was most fixated on, regardless of the characteristics of interpersonal coordination tendencies that emerged when shooting. These findings can be interpreted as evidence of functional perceptual behaviours used to regulate actions needed to ensure precise contact with the ball when shooting at goal. Further, adaptations of fixation patterns, varied between marking defender, goalkeeper, and ball, may provide functional postural orientation to facilitate a successful shot at goal.     

A simple device for detecting departures from visual fixation

A device for detecting departures from visual fixation is described. The principle is to present control targets to one or both eyes at the projected position of the blind spot. When fixation is maintained the control target or targets are not seen. Departures from fixation manifest themselves by the reappearance of the target or targets in the visual field. The system allows approximately 1 deg of movement or less away from the fixation point in either direction.     

Self-motion sensation influenced by visual fixation

Subjects were exposed to angular decelerations of between 1 and 50 deg/sec’ (1) in total darkness, (2) in view of a dim subject-stationary fixation light, or (3) inside an illuminated subject-stationary striped cylinder (conflict stimulation). Vestibularly induced eye movements led to the oculogyral illusion of object motion. This phenomenon can be distinguished from that of the sensation of self-rotation. At the end of deceleration, the initial velocity of self-rotation sensation is similar during all three stimulus conditions, but is reduced in duration with the conflict stimulus. Differences of interpretation in the literature concerning these phenomena can be explained on the basis of the failure to distinguish between the oculogyral illusion and sensation of self-motion and the inability to fully suppress vestibular eye movements.     

Sensitization and dishabituation of infant visual fixation

Dishabituation is defined as the renewed response to a familiarized stimulus upon its retest after the introduction of a novel-stimulus. Two experiments tested an account of dishabituation of infant visual fixation based on the hypothesis that a general, state-dependent sensitization produced by the novel-stimulus energizes responding to any subsequent stimulus. However, this sensitization is thought to be time-dependent, so that increasing delays between the termination of the novel stimuli and the onset of the retest should lead to diminished dishabituation. In Experiment 1, the time between the end of familiarization and the start of the retest of the familiarized pattern was held constant and the temporal location in that inverval of 2 novel stimulus presentations was manipulated. Significant dishabituation was observed only when the novel stimuli occurred shortly before the retest. In Experiment 2, the number of novel-stimulus presentations was systematically manipulated and the magnitude of dishabituation was observed. Significant dishabituation occurred after 2 or 4, but not after 6, novel-stimulus presentations. These findings were consistent with the sensitization explanation of dishabituation, and cast doubt on an explanation of this form of dishabituation based on schema-change.     

Determinants of infant visual fixation: evidence for a two-process theory

Three experiments were conducted to investigate the dynamics of the human infant's (4 months old) visual fixation. The general finding that, over a series of trials, infants fixate longer to a complex than to a simple stimulus was replicated. The function relating fixation time to trials was shown to be nonmonotonic when the stimulus was complex (fixation time increased between Trials 1 and 2 and then decreased), but was monotonic when the stimulus was simple (it decreased systematically over trials). Additional experiments indicated that (a) the nonmonotonic function associated with the complex stimulus was eliminated when the interval separating Trials 1 and 2 was increased from 10 to 20 or 30 s (Experiment 2), and (b) the difference in fixation time between the complex and the simple stimulus was eliminated by controlling their effects in a within-subjects design (Experiment 3). These data challenge the prevailing cognitive-schema theories as a complete account of the dynamics of the infant's visual fixation. A two-process theory that accounts for these data was proposed.     

Two forms of persistence in visual information processing

Iconic memory, which was initially regarded as a unitary phenomenon, has since been subdivided into several components. In the present work we examined the joint effects of two such components (visible persistence and the visual analog representation) on performance in a partial report task. The display consisted of 15 alphabetic characters arranged around the perimeter of an imaginary circle on the face of an oscilloscope. The observer named the character singled out by a bar-probe. Two factors were varied: exposure duration of the array (10, 50, 100, 150, 200, 300, 400 or 500 ms) and duration of blank period (interstimulus interval, ISI) between the termination of the array and the onset of the probe (0, 50, 100, 150, or 200 ms). Performance was progressively impaired as both exposure duration and ISI were increased. The results were explained in terms of a probabilistic combinatorial model in which the timecourses of visible persistence and of the visual analog representation are regarded as time-locked to the onset and to the end of stimulation, respectively. The impairing effect of exposure duration was attributed to the relatively high spatial demands of the task that could be met optimally by information in visible persistence (which declines as a function of exposure duration), but less adequately by information in the visual analog representation. A second experiment, employing a task with lesser spatial demands, confirmed this interpretation.     

Outline forms as visual stimuli in psychological experiments

Summary A set of stimuli to be used in psychological experiments is presented. Drawn spontaneously by the Ss, these stimuli are outline forms which can be freely reproduced in an experimental situation. The complexity and meaning-fulness of 100 forms were investigated. Meaningfulness depended on two variables: the probability of a given form having a certain meaning for a S, and the homogeneity of the meanings a given number of Ss ascribe to this form. Three types of meaningfulness could be distinguished: forms with one meaning only, ambiguous forms and nonsense forms. Complexity, homogeneity and probability of having a meaning are listed for all 100 forms.This research was carried out as part of a doctoral dissertation at the Department of Behavior Science of the Swiss Federal Institute of Technology in Zurich. The author expresses gratitude firstly to his supervisors, Professor H. Fischer and Professor K. Bättig, for their encouragement and criticism throughout the research. Thanks are also due to Professor Klaczko and Dr. H.U. Baumann for their many valuable suggestions, to Laurel Gutmann, Professor A. Flammer and Professor M. Perrez for their many helpful comments on earlier drafts of the paper, and to W.G. Hoffmann and R. Casetti for their further assistance.     

The control of fixation duration in visual search

A study is reported how fixation durations are affected as observers voluntarily use information in the visual environment to direct saccades in search of a target. In experiments with direction-coded displays, search fixation durations for correct and incorrectly directed saccades were comparable during image-driven/bottom-up search. In contrast, for knowledge-driven search, the relationship depended on peripheral preview. With ample access to peripheral preview, search fixation durations preceding correct saccades were shorter than those preceding incorrectly directed saccades. However, they were longer when preview was constrained by a gaze-contingent moving window. Fixation control was modeled as sigmoid functions.     

The interaction of visual and motor memory for graphic forms following tracing

Memory for series of abstract graphic forms was tested using a recognition/ reconstruction procedure in two experiments with 8-9-year-old children. The children either looked at the forms and traced around each of them in turn (VT condition), or looked at the forms for an equivalent length of time and pointed to them (V condition). Memory for the forms, but not their order was improved by tracing. The mechanism responsible for this was investigated by comparing the effects of motor and visual interference interpolated between stimulus presentation and recognition testing. Motor interference was most disruptive in the VT condition while visual interference tended to be most disruptive in the V condition. These results support the proposal that tracing produces a distinct motor memory trace and that this additional source of information aids visual recognition.     

TAM: Explaining off-object fixations and central fixation tendencies as effects of population averaging during search

Understanding how patterns are selected for both recognition and action, in the form of an eye movement, is essential to understanding the mechanisms of visual search. It is argued that selecting a pattern for fixation is time consuming-requiring the pruning of a population of possible saccade vectors to isolate the specific movement to the potential target. To support this position, two experiments are reported showing evidence for off-object fixations, where fixations land between objects rather than directly on objects, and central fixations, where initial saccades land near the center of scenes. Both behaviors were modeled successfully using TAM (Target Acquisition Model; Zelinsky, 2008). TAM interprets these behaviors as expressions of population averaging occurring at different times during saccade target selection. A large population early during search results in the averaging of the entire scene and a central fixation; a smaller population later during search results in averaging between groups of objects and off-object fixations.     

Spontaneous blinks as a criterion of visual fatigue during prolonged work on visual display terminals

Visual fatigue caused by prolonged work viewing a Visual Display Terminals (VDT) and of work reading a hard-copy were assessed by electromyogram (EMG) waveform and electrooculogram (EOG) waveform in spontaneous blinks as objective criteria, and by questionnaire of subjective feeling, and by task performance. The duration and the amplitude of the EMG of the orbicularis ocular muscle on the right side and the EOG of the vertical direction to the eyelid were measured for 10 subjects who participated in a figure task consisting of the addition of single-digit numbers on a VDT work or a work with a hard-copy. The mean values of the duration and the amplitude of the EMG and the EOG were evaluated by the averaging of 10 waveforms of the spontaneous blinks for all subjects. The time lag from the EMG to the EOG in the process of the generation of spontaneous blinks was also analyzed. These five parameters were evaluated during the work time. The mean values for the duration of the EMG increased gradually during the work time, but the amplitude did not show significant difference between the prework and a work time. There was no significant change of the duration of the EOG, but the mean amplitude of the EOG decreased as the work time progressed, and the time lag significantly extended. The blinks frequency increased relatively when using a VDT. The rate of fluctuation for these parameters was higher during use of a VDT than use of a hard-copy. The time lag at five hours of VDT work was extended by 90% based on the value at the pre-work. The symptoms of general fatigue and fatigue of the eyes increased linearly during the VDT work for six hours. The results indicated a significant correlation between the objective parameters for the activity of the spontaneous blinks, i.e., duration and amplitude of EMG and EOG, and the time lag between EMG and EOG, and the subjective feeling was recognized in the time course of the task. These experimental results suggested that the parameters regarding the EMG and the EOG for the spontaneous blinks were effective indices for assessing visual fatigue during prolonged VDT work.     

Characterising the visual buffer: real-world evidence for overwriting early in each fixation

What happens to the pictorial content of fixations when we move our eyes? Previous studies demonstrate that observers are very poor at detecting changes in natural scenes that occur across saccades, blinks, and artificial interruptions ('change blindness'). They suggest that the visual 'snapshots' of what is on the retina during a fixation are not retained and fused over successive fixations. I find similar results when volunteers are performing the complex real-life task of making a cup of tea. Volunteers can access the snapshot of the current fixation but not those of previous fixations. I suggest that volunteers are reporting the content of a low-level visual store that holds a veridical snapshot of the current fixation, rather than the retina itself. The snapshots are not 'wiped' by the saccade and remain in the buffer until they are overwritten by a new snapshot. The overwrite occurs in an all-or-none manner and can be at any time within the first 400 ms of each new fixation, with 50% of overwrites being within the first 100 ms.