Development of the functional visual field

Andries Sanders' dissertation examined selective mechanisms in the functional visual field, and much of his work since has been concerned with the stages that underlie visual information processing particularly while making saccades. We argue that the study of orienting in the functional visual field is timely because it deals with the relation of covert attention shifts, eye movements and head movements to their underlying neurology. In our paper we develop a method to study learning of sequences at all ages from infants to adults. Our studies focus on how learning influences anticipatory eye movements. We examined the learning of unambiguous and context dependent sequences by 4-, 10-, and 18-month-old infants and undergraduates. We found clear learning of unambiguous sequences at 4 months, but learning of context dependent associations was found only in 18-month-olds and in adults. We hypothesize that the learning of unambiguous sequences by 4-month-olds reflects maturation of a basal ganglia-parietal circuit related to adult implicit learning, while the learning of context dependent sequences requires development of frontal structures underlying more general attentional abilities.     

The effect of sleep-loss on processing information in the functional visual field

Two experiments are reported on the effects of sleepstate on performance in a same/different matching task, where two visual signals are presented under visual angles of either 10°, 45°, or 100°. The first study showed a stronger effect of sleep-loss at a more wide display. The effect consists of two parts: one is interpreted as due to the initiation and execution of the shift of gaze from the one to the other signal, and the other to the requirement of integrating successively perceived signals. These interpretations were tested in the second study. It was found that a more pronounced effect of sleep loss occurred when two signals are successively presented, but not when the signals are simultaneously viewed, while preceded by a shift of gaze. The implications of the data are discussed.     

Individual differences in adult foveal visual asymmetries.

The existence and nature of asymmetries in the recognition of elements of a visually presented array have been topics of dispute. In the present study, 32 adults responded to a single vertical or horizontal bar embedded in one circle of a 5 times 7 array of circles by touching a plate corresponding to the orientation of the bar. Two thirds of the subjects were left superior, while one third were right superior. Performance was in general top superior and decreased with increasing distance from the center. Possible explanations for these asymmetries are examined in terms of sequential processing, acuity dominance, hemispheric specialization, and selective attention.     

The effects of perceptual load in central and peripheral regions of the visual field

The perceptual load model claims that attentional selectively depends on perceptual load. Selectivity is high with high load, but low with low load. Previous studies only manipulated load levels at task-relevant regions. In this study, perceptual load was orthogonally manipulated in both relevant (central) and nonrelevant (peripheral) regions, by varying the similarity between the target and nontarget letters and the nontarget letters' heterogeneity. The participants had to identify a target-letter appearing in a central circle of letters. A distractor-letter, appearing in a peripheral circle, was compatible, neutral, or incompatible with the target. As expected, increasing peripheral load deteriorated performance, but only with low levels of central load. The pattern of distractor interference did not follow the model's predictions because distractor interference under high load levels was occasionally found. The expected pattern of results emerged only when the spatial uncertainty regarding the distractor position was low, implying that spatial uncertainty plays an important role in attentional selectivity.     

Processing differences between memory search and foveal visual search

The ability to detect small differences in the positions of two lines (vernier acuity) showed some improvement with practice in all eight subjects, even for subjects given no error feedback. The average decline in threshold with training (2,000–2,500 responses) was about 40%. We used three target orientations: vertical, horizontal, and right oblique. Orientational differences remained stable in only one subject. In five subjects, orientational differences present at the beginning of training diminished or disappeared with increased experience; in two, they increased.     

Effects of memory load on visual search

It remains unclear how memory load affects attentional processes in visual search (VS). No effects, as well as beneficial and detrimental effects of memory load, have been found in this type of task. The main goal of the present research was to explore whether memory load has a modulating effect on VS by means of a different attentional set induced by the order of trials (mixed vs. blocked) and by the time presentation of visual display (long vs. short). In Experiment 1, we randomized the order of type of trial (5, 10 and 15 items presented in the display) while it remained constant (10 items) in Experiments 2A and 2B. In the later experiments, we also changed time presentation of visual display (3000 vs. 1300 ms, respectively). Results showed no differential effects of memory load in Experiments 1 and 2A, but they showed up in Experiment 2B: RTs were longer in the attentional task for trials under high memory load conditions. Although our hypothesis of the attentional set is supported by the results, other theoretical implications are also worth discussing in order to better understand how memory load may modulate attentional processes in VS.     

Raised visual detection thresholds depend on the level of complexity of cognitive foveal loading.

The objective of the study was to measure the interactions between visual thresholds for a simple light (the secondary task) presented peripherally and a simultaneously performed cognitive task (the primary task) presented foveally The primary task was highly visible but varied according to its cognitive complexity. Interactions between the tasks were determined by measuring detection thresholds for the peripheral task and accuracy of performance of the foveal task. Effects were measured for 5, 10, 20, and 30 deg eccentricity of the peripherally presented light and for three levels of cognitive complexity. Mesopic conditions (0.5 lx) were used. As expected, the concurrent presentation of the foveal cognitive task reduced peripheral sensitivity. Moreover, performance of the foveal task was adversely affected when conducting the peripheral task. Performance on both tasks was reduced as the level of complexity of the cognitive task increased. There were qualitative differences in task interactions between the central 10 deg and at greater eccentricities. Within 10 deg there was a disproportionate effect of eccentricity, previously interpreted as the 'tunnel-vision' model of visual field narrowing. Interactions outside 10 deg were less affected by eccentricity. These results are discussed in terms of the known neurophysiological characteristics of the primary visual pathway.     

Influence of differences of visual acuity in various visual field conditions on spectral characteristics of the center of pressure sway

This study examined the influence of visual acuity and visual field on the spectral characteristics of the center of pressure during standing. 17 men and 20 women participated in High and Low visual acuity groups. Both groups underwent center of pressure measurements under three visual field conditions: No vision: subjects were given no visual information, Central vision: they were given only central visual field information, and Full vision: they were given full visual information. To assess the spectral characteristics of center of pressure, mean power frequency and frequency of maximal power were calculated from medial-lateral and anterior-posterior center of pressure directions. The Friedman test and Scheffé pairwise comparison tests showed that frequency of maximal power was higher in the No vision than in the Central and Full vision conditions in the High visual acuity group. In conclusion, people with high visual acuity are more susceptible to visual field conditions than those with low visual acuity. It is suggested that postural control characteristics differ with visual acuity or resolution in the central visual field.     

Expansion of the functional visual field and context skipping in a continuous search task

Summary A new experimental paradigm for the investigation of visual search processes is presented. In a continuous visual search task, the target occurs several times in each search list, and a response is required to each occurrence of the target. The analysis of the data is based on the regression of the interresponse intervals on the distance between successive target occurrences. With a view to measure the size of the functional visual field and the efficiency of skipping strategies, the size of letter groups and the minimal distance between successive target occurrences were varied. The rate parameter of the regression functions was used to infer the extent of the functional visual field; the efficiency of skipping was assessed on the basis of the intercept. A U-shaped relationship between the size of letter groups and the rate parameter of the regression functions was predicted and found; during practice, the minimum of the U-function shifted from small to large group sizes. This was taken as an indication that the functional visual field expands during practice in a continuous search task. Evidence for efficient skipping strategies was found at all stages of practice, subject to the constraint that there was a natural relationship between the size of letter groups and the minimal distance between target occurrences.Extended version of a paper given at the 19th Tagung experimentell arbeitender Psychologen, Konstanz 1977. This paper is based on experimental work reported in the Diplom-Arbeiten by Layla Hanning, Ursula Schmidt and Wolfgang Wojde (Psychologisches Institut, Ruhr-Universität Bochum 1977)     

Measurement of the visual field

There is increasing evidence that concurrent visual and nonvisual tasks not only reduce the size but also result in systematic deformation of the visual field. Given such complex changes in the visual field, appropriate representation and measurement of its shape is all important. Shape measures utilized by researchers and reported in the literature should also be sufficiently standardized to allow comparison of results across experiments.     

Sex differences in functional brain activation during a lexical visual field task

Functional MRI was used to investigate sex differences in brain activation during a paradigm similar to a lexical-decision task. Six males and 6 females performed two runs of the lexical visual field task (i.e., deciding which visual field a word compared with a pseudoword was presented to). A sex difference was noted behaviorally: The reaction time data showed males had a marginal right visual field advantage and women a left visual field advantage. Imaging results showed that men had a strongly left-lateralized pattern of activation, e.g., inferior frontal and fusiform gyrus, while women showed a more symmetrical pattern in language related areas with greater right-frontal and right-middle-temporal activation. The data show evidence of task-specific sex differences in the cerebral organization of language processing.     

Perceptual load alters visual excitability

Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load should affect simultaneous, but not sequential, stimulus presentations, the visual excitability account makes the novel prediction that load should affect detection sensitivity for both simultaneous and sequential presentations. Participants fixated a stimulus stream, responding to targets defined by either a color (low load) or color and orientation conjunctions (high load). Additionally, detection sensitivity was measured for a peripheral critical stimulus (CS) presented occasionally. Increasing load at fixation reduced sensitivity to the peripheral CSs; this effect was similar regardless of whether CSs were presented simultaneously with central stimuli or during the (otherwise empty) interval between them. Controls ruled out explanations of the results in terms of strategic task prioritization. These findings support a cortical excitability account for perceptual load, challenging stimulus competition accounts.     

Cognitive load effects on early visual perceptual processing

Contrast-based early visual processing has largely been considered to involve autonomous processes that do not need the support of cognitive resources. However, as spatial attention is known to modulate early visual perceptual processing, we explored whether cognitive load could similarly impact contrast-based perception. We used a dual-task paradigm to assess the impact of a concurrent working memory task on the performance of three different early visual tasks. The results from Experiment 1 suggest that cognitive load can modulate early visual processing. No effects of cognitive load were seen in Experiments 2 or 3. Together, the findings provide evidence that under some circumstances cognitive load effects can penetrate the early stages of visual processing and that higher cognitive function and early perceptual processing may not be as independent as was once thought.     

Musical expertise modulates the effects of visual perceptual load

Several studies have demonstrated that faces are processed differently from other types of objects, implicating a special role that faces have within the human visual system. However, other studies have suggested that faces may be special only in that they constitute a highly familiar category of visual objects with which most humans have expertise. In this study, we tested a group of expert musicians with a musical instrument classification task during which irrelevant images of musical instruments were presented as visual distractors under varying conditions of perceptual load. Unlike nonmusicians (who had been tested in Lavie, Ro, & Russell, 2003, using the same paradigm as in the present study), the musicians processed these irrelevant images of musical instruments even under conditions of high perceptual load. These results suggest that musical instruments are processed automatically and without capacity limits in subjects with musical expertise and implicate a specialized processing mechanism for objects of high familiarity.     

Brightness perception in the visual field

Summary Apparent brightness was measured at different positions in the visual field for scotopic, mesopic, and photopic adaptation levels by means of a magnitude estimation technique. Apparent brightness of targets with a given luminance remained rather constant throughout the visual field for the mesopic and photopic adaptation level; for the scotopic adaptation level targets in the foveal and perifoveal area had to be more intense in order to appear as bright as targets in the far periphery (beyond 20° eccentricity). For the photopic range, two brightness power functions with different exponents were obtained for the luminance range from 1 to 100 mL at each eccentricity. The exponent for the range from 1 to 10 mL is considerably greater than the exponent beyond 10 mL, and appears to increase with increasing eccentricity.The experiments described in this paper were partly supported by Deutsche Forschungsgemeinschaft and SFB 50-C 6.     

Figural preference and the visual field

Three experiments tested a hypothesis that the shape and relative dimensions of the binocular visual field determine a preference for rectangles possessing dimensions similar to those of the golden section. The results were that Ss horizontally oriented the rectangles they had drawn in correspondence with the shape of the binocular visual field but when Ss chose the most pleasing rectangles there was no significant preference for rectangles whose long side was horizontal. For all experiments there was little preference for rectangles whose ratio of short to long side approximated the golden section. There was some evidence that the placement of the rectangles with respect to the background affects preference.     

Effects of visual attentional load on low-level auditory scene analysis

The sharing of processing resources between the senses was investigated by examining the effects of visual task load on auditory event-related brain potentials (ERPs). In Experiment 1, participants completed both a zero-back and a one-back visual task while a tone pattern or a harmonic series was presented. N1 and P2 waves were modulated by visual task difficulty, but neither mismatch negativity (MMN) elicited by deviant stimuli from the tone pattern nor object-related negativity (ORN) elicited by mistuning from the harmonic series was affected. In Experiment 2, participants responded to identity (what) or location (where) in vision, while ignoring sounds alternating in either pitch (what) or location (where). Auditory ERP modulations were consistent with task difficulty, rather than with task specificity. In Experiment 3, we investigated auditory ERP generation under conditions of no visual task. The results are discussed with respect to a distinction between process-general (N1 and P2) and processspecific (MMN and ORN) auditory ERPs.