Effect of static visual acuity on dynamic visual acuity: a pilot study

The aim of this pilot study was to evaluate whether dynamic visual acuity changes with or without refractive correction. 42 healthy enrolled subjects with normal vision were divided into two age-matched groups. In Group A, dynamic visual acuity was measured first with the refractive error fully corrected and then without. In Group B, dynamic visual acuity measurements were taken in the reverse order of that performed by Group A. The measurements were binocularly performed five times using free-head viewing after dynamic visual acuity values were stable. Significant changes in dynamic visual acuity (static visual acuity 20/20 vs 12/20) were observed in both Group A (171.6 +/- 36.0 deg./sec. vs 151.8 +/- 39.6 deg./sec., Wilcoxon test, p < .001) and Group B (169.8 +/- 30.0 deg./sec. vs 151.2 +/- 36.0 deg./sec., Wilcoxon test, p < .001). The interaction was significant (F1.20 = 8.12, p = .009). These results indicated that refractive correction affected dynamic visual acuity.     

Dynamic visual capture: apparent auditory motion induced by a moving visual target

Apparent motion of a sound source can be induced by a moving visual target. The direction of the perceived motion of the sound source is the same as that of the visual target, but the subjective velocity of the sound source is 25-50% of that of the visual target measured under the same conditions. Eye tracking of the light target tends to enhance the apparent motion of the sound, but is not a prerequisite for its occurrence. The findings are discussed in connection with the 'visual capture' or 'ventriloquism' effect.     

How visual system configuration can play a role in individual recognition: a visual modeling study

Animal Cognition - Many species rely on individual recognition (i.e., the use of individual signals to identify and remember a conspecific) to tune their social interactions. However, little is...     

Prioritization in visual search: visual marking is not dependent on a mnemonic search

Visual marking (VM) refers to our ability to completely exclude old items from search when new stimuli are presented in our visual field. We examined whether this ability reflects an attentional scan of the old items, possibly allowing observers to apply inhibition of return or maintain a memory representation of already seen locations. In four experiments, we compared performance in two search conditions. In the double-search (DS) condition, we required participants to pay attention to a first set of items by having them search for a target within the set. Subsequently, they had to search a second set while the old items remained in the field. In the VM condition, the participants expected the target only to be in the second (new) set. Selection of new items in the DS condition was relatively poor and was always worse than would be expected if only the new stimuli had been searched. In contrast, selection of the new items in the VM condition was good and was equal to what would be expected if there had been an exclusive search of the new stimuli. These results were not altered when differences in Set 1 difficulty, task switching, and response generation were controlled for. We conclude that the mechanism of VM is distinct from mnemonic and/or serial inhibition-of-return processes as involved in search, although we also discuss possible links to more global and flexible inhibition-of-return processes not necessarily related to search.     

RAP: a new framework for visual categorization

Cognitive science might almost be defined as several disciplines communicating their different perspectives on the mind, the common object of study. However, domain-specific concepts and techniques can prevent, rather than foster, a communication of viewpoints. In this article, we develop a new framework for visual categorization in which the interaction between Represented (R) information and Available (A) information determine the Potent (P) information (symbolically, R ? A approximately P). We argue and illustrate that this framework helps to establish a common language to articulate issues common to low-, mid-, and high-level vision. More importantly, we present new techniques with which to visualize the so-far elusive constructs of representation and potent information.     

Prosopagnosia: a defect in visual configural processing

A patient with severe, lasting prosopagnosia could not get an immediate overview of a face sufficiently specific for successful identification. He also failed completely in tasks of visual closure despite adequate performances on numerous other tests of visual perception and memory. We conclude that prosopagnosia represents a loss of visual "configural processing"--a learned skill enabling immediate identification of individual members of a class without conscious visuospatial analysis or remembering. Prosopagnosia and agnosic alexia represent two distinct defects of configural processing: Alexics cannot identify items with distinctive features that are themselves identifiable. Prosopagnosics cannot identify objects whose critical distinguishing features have no independent identities.     

Development of visual attention: a stereoscopic view

Five-year-olds, 8-year-olds, and adults (20 each) tachistoscopically viewed random-dot stereograms containing either uniform depth or an elevated disk whose perimeter fell 1.5 degrees, 2.5 degrees, or 4 degrees beyond fixation. When subjects were forewarned as to the size of the disk to look for (precued trials), signal detection improved (d' increased) for all three groups, and 5-year-olds improved the most. Without forewarning (self-cued trials), the 5-year-olds performed more poorly than the other two groups, which performed alike. Although young children are able to allocate their visual attention selectively, they do not appear to deploy it as quickly or as effectively as their elders when the focus of attention is theirs to choose.     

The vista paradox: a natural visual illusion

Suppose an observer views a distant object through a window in the far wall of a room or corridor--a visual scene constituting a vista. If the observer moves toward the window, then the distant object will shrink in apparent size and appear farther away. These effects are paradoxical, because the distant object appears smaller as its visual angle increases. The vista paradox occurs under many other real-world conditions, such as viewing a distant object while moving out of the mouth of a valley, or driving across a topographic crest. In the present study, framing effects and the equidistance tendency are considered as possible factors. However, an explanation based on the dynamic relationship between the visual angle of the framing portion of a vista and the visual angle of a distant object appears more promising.     

Comparative visual search: a difference that makes a difference

In this article we present a new experimental paradigm: comparative visual search. Each half of a display contains simple geometrical objects of three different colors and forms. The two display halves are identical except for one object mismatched in either color or form. The subject's task is to find this mismatch. We illustrate the potential of this paradigm for investigating the underlying complex processes of perception and cognition by means of an eye-tracking study. Three possible search strategies are outlined, discussed, and reexamined on the basis of experimental results. Each strategy is characterized by the way it partitions the field of objects into "chunks." These strategies are: (i) Stimulus-wise scanning with minimization of total scan path length (a "traveling salesman" strategy), (ii) scanning of the objects in fixed-size areas (a "searchlight" strategy), and (iii) scanning of object sets based on variably sized clusters defined by object density and heterogeneity (a "clustering" strategy). To elucidate the processes underlying comparative visual search, we introduce besides object density a new entropy-based measure for object heterogeneity. The effects of local density and entropy on several basic and derived eye-movement variables clearly rule out the traveling salesman strategy, but are most compatible with the clustering strategy.     

Temporal constraints on visual learning: a computational model

Given a constant stream of perceptual stimuli, how can the underlying invariances associated with a given input be learned? One approach consists of using generic truths about the spatiotemporal structure of the physical world as constraints on the types of quantities learned. The learning methodology employed here embodies one such truth: that perceptually salient properties (such as stereo disparity) tend to vary smoothly over time. Unfortunately, the units of an artificial neural network tend to encode superficial image properties, such as individual grey-level pixel values, which vary rapidly over time. However, if the states of units are constrained to vary slowly, then the network is forced to learn a smoothly varying function of the training data. We implemented this temporal-smoothness constraint in a backpropagation network which learned stereo disparity from random-dot stereograms. Temporal smoothness was formalized with the use of regularization theory by modifying the standard cost function minimised during training of a network. Temporal smoothness was found to be similar to other techniques for improving generalisation, such as early stopping and weight decay. However, in contrast to these, the theoretical underpinnings of temporal smoothing are intimately related to fundamental characteristics of the physical world. Results are discussed in terms of regularization theory and the physically realistic assumptions upon which temporal smoothing is based.     

View combination: a generalization mechanism for visual recognition

We examined whether view combination mechanisms shown to underlie object and scene recognition can integrate visual information across views that have little or no three-dimensional information at either the object or scene level. In three experiments, people learned four “views” of a two dimensional visual array derived from a three-dimensional scene. In Experiments 1 and 2, the stimuli were arrays of colored rectangles that preserved the relative sizes, distances, and angles among objects in the original scene, as well as the original occlusion relations. Participants recognized a novel central view more efficiently than any of the Trained views, which in turn were recognized more efficiently than equidistant novel views. Experiment 2 eliminated presentation frequency as an explanation for this effect. Experiment 3 used colored dots that preserved only identity and relative location information, which resulted in a weaker effect, though still one that was inconsistent with both part-based and normalization accounts of recognition. We argue that, for recognition processes to function so effectively with such minimalist stimuli, view combination must be a very general and fundamental mechanism, potentially enabling both visual recognition and categorization.     

Psychometric intelligence and visual evoked potentials: a replication

Previously we have reported significant correlations between EEG visual evoked potential (EP) parameters and scores on the Raven's Advanced Progressive Matrices (RAPM) test. This study is an attempt to replicate those findings in a new sample of 27 S s. The results provide further evidence that EP amplitude is related to intelligence-test performance. There is also confirmation that stimulus luminance levels influence the magnitude of EP amplitude/intelligence correlations. In addition, the results indicate that age may be a confounding variable.     

Age-related change in visual information processing: Toward a unified theory of aging and visual memory

Memory for semantic information is relatively preserved through the normal aging process. Visuospatial memory remains less intact. In the present article a theory is proposed that links this processing difference to normal age-related generalized cognitive slowing, and to the appearance of specific age-related differences in memory performance. Evidence for these suggestions is presented from work in four areas: mental rotation, spatial memory, paired-associates learning, and free recall. Cognitive performance in young and older respondents is shown to vary predictably with systematic variation of visuospatial and semantic stimulus factors consistent with these hypotheses. A further test of these ideas derives from the development of a clinically useful mnemonic system for older adults that is based on these principles. Taken together, this research indicates that much of the deficit observed in the memory performance of older adults may derive not from memory problems per se, but rather from the action of generalized cognitive slowing, which contributes to diminished abilities to represent and process visual images. This series of findings may provide a framework for understanding a wide variety of the processes involved in aging and visual memory, and for the creation of applications to aid the memory of older adults.     

The effect of a visual indicator on rate of visual search: Evidence for processing control

Search rates were estirnated from response latencies in a visual search task of the type used by Atkinson, Holmgren, and Juola (1969), in which a S searches a small set of letters to determine the presence or absence of a predesignated target. Half of the visual displays contained a marker above one of the letters. The marked letter was the only one that had to be checked to determine whether or not the display contained the target. The presence of a marker in a display significantly increased the estimated rate of search, but the data clearly indicated that Ss did not restrict processing to the marked item. Letters in the vicinity of the marker were also processed. These results were interpreted as showing that Ss are able to exercise some degree of control over the search process in this type of task.