Showing papers on "Visual perception published in 1983"

The Logic of Perception

Abstract: The theory of visual perception that Irvin Rock develops and supports in this book with numerous original experiments, views perception as the outcome of a process of unconscious inference, problem solving, and the building of structural descriptions of the external world. It is a radical departure from his earlier work and contrasts with traditional perceptual theories like those of James J. Gibson or the Gestalt view.Rock experiments with a series of phenomena, like motion perception, illusory contours, and size and brightness constancy, and shows that they can be understood in terms of the knowledge applied by the visual system to the interpretation of the retinal image. His work largely complements that being done in artificial intelligence, demonstrating that the visual system is far more subtle and intelligent in many tasks which have not yet been modelled on the computer.Irvin Rock, a noted investigator of perceptual phenomena for nearly three decades, is Professor of Psychology at Rutgers University.

Perception of numerical invariance in neonates.

Abstract: 40 healthy, normal newborn infants were evaluated with reference to their ability to discriminate among visual stimulus arrays consisting of 2 versus 3 or 4 versus 6 black dots. Infants made this discrimination within a habituation/dishabituation paradigm for the small number sets (2 to 3 and 3 to 2) but not for the larger sets (4 to 6 and 6 to 4). We argue that this suggests the ability to abstract numerical invariance from small-set visual arrays and may be evidence for complex information processing during the first week of life.

Incidence of Visual Field Loss in 20,000 Eyes and Its Relationship to Driving Performance

Abstract: Automated visual field screening of 10,000 volunteers (20,000 eyes) showed the incidence of visual field loss was 30% to 35% for persons aged 16 to 60 years but was approximately 130% for those older than 65 years Approximately half of the persons with abnormal visual fields were previously unaware of any problem with peripheral vision Follow-up results suggested that the most common causes of visual field loss were glaucoma, retinal disorders, and cataracts Drivers with binocular visual field loss had accident and conviction rates twice as high as those with normal visual fields Drivers with monocular visual field loss had accident and conviction rates equivalent to those of a control group Our results have important implications for mass visual field screening to detect eye diseases and for vision-related factors in traffic safety

Is continuous visual monitoring necessary in visually guided locomotion

Abstract: Subjects were asked to walk to targets that were up to 21 m away, either with vision excluded during walking or under normal visual control. Over the entire range, subjects were accurate whether or not vision was available as long as no more than approximately 8 sec elapsed between closing the eyes and reaching the target. If more than 8 sec elapsed, (a) this had no influence on distances up to 5 m, but (b) distances between 6-21 m were severely impaired. The results are interpreted to mean that two mechanisms are involved in guidance. Up to 5 m, motor programs of relatively long duration can be formulated and used to control activity. Over greater distances, subjects internalized information about the environment in a more general form, independently of any particular set of motor instructions, and used this to control activity and formulate new motor programs. Experiments in support of this interpretation are presented.

On the Role of Structure in Vision

Abstract: People are able to perceive structure in images, apart from the perception of tri-dimensionality, and apart from the recognition of familiar objects. We impose organization on data (noticing flow fields, regularity, repetition, etc.) even when we have no idea what it is we are organizing. What is remarkable is the degree to which such naively perceived structure survives more or less intact once a semantic context is established: the naive observer often sees essentially the same things an expert does, the difference between naive and informed perception often amounting to little more than labeling the perceptual primitives. It is almost as if the visual system has some basis for guessing what is important without knowing why. Our objective in this paper is to understand the role of primitive structure in visual perception. What does this level of organization mean? What, if anything, is it good for? If it is useful, how do we get it and, once gotten, use it? We will argue that perceptual organization is a primitive level of inference, the basis for which lies in the relation between structural and causal unity: the appearance of spatiotemporal coherence or regularity is so unlikely to arise by the chance interaction of independent entities that such regular structure, when observed, almost certainly denotes some underlying unified cause or process. This view will be shown to have broad implications for computational theories of vision, providing a unifying framework for many current techniques of early and intermediate vision, and enabling a style of interpretation more in keeping with the qualitative and holistic character of human vision.

The impending demise of the icon: A critique of the concept of iconic storage in visual information processing

Abstract: Without disputing the experimental evidence that subjects have available most of the content of brief displays for a fraction of a second, or that visual stimuli Persist after their physical termination for a similar time, I argue that this evidence is irrelevant to perception. Specifically, the notion of an icon as a brief storage of information persisting after stimulus termination cannot possibly be useful in any typical visual information-processing task except reading in a lightning storm. Since the visual world that provides the stimuli for perception is continuous and not chopped up by tachistoscopes, and since our eyes and heads are rarely motionless, no realistic circumstances exist in which having a frozen iconic storage of information could be helpful. Rather, the presence of such an icon interferes with perception. This paper examines instances of normal perception, and then reviews experimental evidence on temporal integration, saccadic suppression, masking, and the photoreceptor basis of visual persistence, to further demonstrate that a storage of excitation cannot be a useful device for storing information. Finally, I note that little would have to be changed in our theories of visual perception or information processing if we simply forgot all about the icon and iconic memory as an early stage of processing.

What does the eye see best

Abstract: Our eyes see so much in such varied conditions that one might consider the question posed in the title to be meaningless, but we show here that, within the range that we have been able to test, there is a particular spatiotemporal pattern of light that is detected better than any other. At least two plausible theories of visual detection predict that a stimulus will be seen best (will have greatest quantum efficiency) when it matches the weighting function of the most efficient detector. We have measured quantum efficiency for detecting a wide variety of spatiotemporal patterns using foveal vision in bright light. The best stimulus found so far is a small, briefly exposed circular patch of sinusoidal grating having a spatial frequency of approximately 7 c deg-1, drifting at approximately 4 Hz. We propose that this is the weighting function of the most efficient human contrast detector. We believe this answer to the question is unexpected and may have fundamental implications with regard to the mechanisms of visual perception.

The role of vision in "visual imagery" experiments: Evidence from the congenitally blind.

Abstract: SUMMARY Responses of congenitally blind subjects were compared with those of sighted subjects to test whether performance on three "visual imagery" tasks is dependent on specifically visual processing. In Experiment 1, subjects memorized the locations of several figures on a board and then were asked to form an image of the board and mentally to "scan" from one figure to another. There was a strong relationship between distance and scanning time both for blind and for sighted subjects, although the response times were significantly longer for blind than for sighted subjects. Thus the images of congenitally blind subjects, like those of sighted subjects, preserve metric spatial information. Experiment 2 varied the subjective size of imaged objects by requiring subjects to form images of a "target" object, such as a radio, alongside a "context" object that was either very large (a car) or very small (a paper clip). Subjects then were asked to verify whether a named physical attribute such as "drawer" or "dial" was a part of the imaged target object (radio). For both blind and sighted subjects, the time taken to verify whether a physical feature of a target object was included in the image was greater when the context item was large so that the target object was subjectively small. Thus for blind as well as for sighted subjects the features of a subjectively large image are noticed or accessed faster than those of a subjectively small image. Experiment 3 tested the mnemonic consequences of forming images of objects with differing spatial relationships to each other. Subjects heard descriptions and were instructed to form images of scenes in which a target object was described in one of three relationships to the rest of the scene: spatially separated, contiguous but visually hidden or concealed, or contiguous and clearly visible. The pattern of results on an incidental cued-recall test was similar for blind and sighted subjects, with objects imaged as spatially contiguous recalled better than those that were spatially separated. Visual "picturability" did not affect recall. Overall recall scores did not differ for blind and sighted subjects, but sighted subjects reported forming the images significantly faster than did the blind. Thus the images formed by blind subjects were as mnemonically effective as those created by sighted subjects and the memorability of imaged scenes was equivalently affected by the spatial relationships of their components. Taken together, the three experiments demonstrate that congenitally blind adults are capable of preserving and processing spatial images in a manner very similar to that used by sighted subjects, although such processing may require slightly less time with visually mediated than with nonvisually mediated imagery. The research raises questions about definitions of imagery that are tied specifically to the visual processing system and suggests that spatial imagery processing ability need not depend on visual perceptual experience or, in fact, on any specific sensory processing modality.

Role of corollary discharge in space constancy.

Abstract: Visual fixation can be maintained in spite of finger pressure on the monocularly viewing eye. We measured the amount of extraocular muscle effort required to counter the eyepress as the secondary deviation of the occluded fellow eye. Using this method, without drugs or neurological lesions, we have shown that corollary discharge (CD) governs perception of position of a luminous point in darkness, that is, an unstructured visual field. CD also controls visuomotor coordination measured with open-loop pointing and the matching of visual and auditory direction in light and in darkness. The incorrectly biased CD is superseded byvisual position perception in normal structured environments, a phenomenon we call visual capture of Matin. When the structured visual field is extinguished, leaving only a luminous point, gradual release from visual capture and return to the biased CD direction follows after a delay of about 5 sec.

Evidence against visual integration across saccadic eye movements

Abstract: One of the classic problems in perception concerns how we perceive a stable, continuous visual world even though we view it via a temporally discontinuous series of eye movements. Previous investigators have suggested that our perception of a stable visual environment is due to anintegrative visual buffer, a special memory store capable of fusing the visual contents of successive fixations according to their environmental coordinates. In this paper, three experiments are reported that attempted to demonstrate the existence of an integrative visual buffer. The experimental procedure required subjects to mentally fuse two halves of a dot matrix presented in the same spatial region of a display, but separated by an eye movement so that each half was viewed only during one fixation. Thus, subjects had to integrate packets of visual information that had the same environmental coordinates, but different retinal coordinates. No evidence was found in any experiment for the fusion of visual information from successive fixations in memory, leaving the status of the integrative visual buffer in serious doubt.

The Lie transformation group model of visual perception.

Abstract: The Lie transformation group model of neuropsychology (LTG/NP) purports to represent and explain how the locally smooth processes observed in the visual field, and their integration into the global field of visual phenomena, are consequences of special properties of the underlying neuronal complex. These properties are modeled by a specific set of mathematical structures that account both for local (infinitesimal) operations and for their generation of the “integral curves” that are visual contours. The purpose of this tutorial paper is to expound, as nontechnically as possible, the mathematical basis for LTG/NP, and to evaluate that model against a reasonable set of criteria for a neuropsychological theory. It is shown that this approach to spatial vision is closer to the mainstream of current theoretical work than might be assumed; recent experimental support for LTG/NP is described.

Evaluation and integration of visual and auditory information in speech perception.

Abstract: Three experiments were carried out to investigate the evaluation and integration of visual and auditory information in speech perception. In the first two experiments, subjects identified /ba/ or /da/ speech events consisting of high-quality synthetic syllables ranging from /ba/ to /da/ combined with a videotaped /ba/ or /da/ or neutral articulation. Although subjects were specifically instructed to report what they heard, visual articulation made a large contribution to identification. The tests of quantitative models provide evidence for the integration of continuous and independent, as opposed to discrete or nonindependent, sources of information. The reaction times for identification were primarily correlated with the perceived ambiguity of the speech event. In a third experiment, the speech events were identified with an unconstrained set of response alternatives. In addition to /ba/ and /da/ responses, the /bda/ and /tha/ responses were well described by a combination of continuous and independent features. This body of results provides strong evidence for a fuzzy logical model of perceptual recognition.

Rapid discrimination of visual patterns

Abstract: Experiments involving the rapid discrimination of visual patterns are used to infer the spatial information available to an observer within the first few hundred ms of inspection. Eye movements are prevented by a very brief presentation of the stimulus, and the inspection interval is terminated by a presentation of a masking pattern. It is shown that detection of a single vertical target line segment, embedded in an array of differently oriented background segments, improves with the increase of mask delay. The reduction of the area in which the target may lie reduces the inspection time that is required to determine the target's presence or absence. The phenomena are invariant under changes of the spatial scale within the fovea and parafovea. These results are interpreted in the context of a model in which the diameter of the area which can be searched in parallel is proportional to the distance in a feature space between the target and background elements. The geometry of this feature space is similar to the functional architecture of the visual cortex. A theory of texture perception based on a qualitative all-or-none feature space of textons is described. A quantitative model that is shown to be essentially equivalent to the previous theory in the limiting case of very large feature differences is proposed.

Infants' perception of substance and temporal synchrony in multimodal events*

Abstract: Four-month-old infants can detect a relationship between the soundtracks and films of rigid and elastic objects in motion. When movies of these two kinds of objects were shown side by side along with the soundtrack to one of them, infants predominately watched the sound films. Three subsequent studies explored the basis of this intermodal perception. It was found that infants detected bimodal temporal structure specifying object rigidity and elasticity, and temporal synchrony between the sights and sounds of object impact. These results support the view that the development of intermodal perception is based on the detection of invariant relations in visual and acoustic stimulation.

Colour-generating interactions across the corpus callosum

Abstract: Human vision has the remarkable property that, over a wide range, changes in the wavelength composition of the source light illuminating a scene result in very little change in the colour of any of the objects. This colour constancy can be explained by the retinex theory, which predicts the colour of a point on any object from a computed relationship between the radiation from that point and the radiation from all the other points in the field of view (Fig. 1). Thus the computations for colour perception occur across large distances in the visual field. It has not been clear, however, whether these long-range interactions take place in the retina or the cortex. Reports that long-range colour interactions can be reproduced binocularly when one band of wavelengths enters one eye and a different band enters the other might seem to establish the cortex as the site of the computation. Many observers, however, see very unsatisfactory colour or no colour at all in this binocular situation, suggesting that the cortex may not be the only site at which the computation is carried out, or even the most important site. We have now tested the role of the cortex in a human subject in whom the nerve fibres connecting cortical areas subserving two separate parts of the visual field had been severed, and find that the cortex is necessary for long-range colour computations.

Failure to integrate information from successive fixations

Abstract: optic nerve crush [M. G. Yoon, J. Physiol. (London) 257, 621 (1976); R. L. Meyer, J. Comp. Neurol. 189, 175 (1980)]. Ultrastructural studies show that a few retinotectal synapses reappear 3 to 4 weeks after optic nerve crush [L. R. Marotte and R. E. Mark, Exp. Neurol. 49, 772 (1975); M. Murray, J. Comp. Neurol. 168, 175 (1976)]. The recovery of synaptic density to a normal level, however, appears to take several months [M. Murray and M. A. Edwards, ibid. 209, 363 (1982)]. 8. P. H. O'Farrell, J. Biol. Chem. 250, 4007 (1975). The modifications we used are described by P. Strocchi et al. [J. Neurochem. 37, 1295 (1981)]. The lysis buffer and the gels contained 6 percent Ampholine, pH ranges 3.5 to 5, 5 to 7, and 3.5 to 10 (LKB) in the ratio 2:2:1. 9. W. M. Bonner and R. A. Laskey, Eur. J. Biochem. 46, 83 (1974). 10. A rapidly transported 24K protein which is selectively enhanced in the frog regenerating optic nerve does not ordinarily migrate out of isoelectric focusing gels into SDS slab gels unless high concentrations of urea are present in the latter [J. H. P. Skene and M. Willard, J. Neurosci. 1, 419 (1981)]. In our two-dimensional gels, the absence of a 26K protein that is differentially regulated by the tectum may be accounted for by such solubilization properties. Alternatively, the isoelectric point of the 26K protein may be outside the range of our gel system. 11. In other experiments (M. G. Yoon, L. I. Benowitz, F. Baker, in preparation), we crushed both optic nerves and ablated only one tectum. The differences in rapidly transported proteins seen in the two nerves of these animals were found to be similar to the differences between R+T and R-T groups described in the present report. This result suggests that diffusible factors deriving from the one intact tectum are not causing the two retinas to express similar proteins, and implies that the differences between R+T and R-T nerves reported here are likely to be mediated by surface-contact events. 12. Supported by National Institute of Neurological and Communicative Disorders and Stroke grant ROINS16943 (to L.I.B.) and by grants MT 4994 from the Medical Research Council and A 9756 from the Natural Sciences and Engineering Research Council of Canada (to M.G.Y.). We thank F. Baker for technical assistance.

Children's Television Viewing: Attention and Comprehension of Auditory versus Visual Information.

Abstract: This study examines the relationship between children's attention and comprehension of auditory and visual information on television. 60 5-year-olds viewed a videotape of "Sesame Street" and were then asked comprehension questions. Equal numbers of children viewed the television with (a) toys available to play with (the visual attention manipulation); (b) a record playing in the room (the auditory attention manipulation); or (c) no toys or record available (the control condition). All children viewed the same television sequence, which consisted of (a) visual segments, (b) auditory segments, and (c) mixed modality segments. The major results were that the children effectively distributed their attention such that they could process auditory and visual information from television while performing other activities. Further, the children were sensitive to which segments required visual attention and which did not, and they were able to spontaneously adjust their pattern of visual attention appropriately. These results indicate that children utilize a fairly sophisticated cognitive processing strategy while watching television.

An outlying visual area in the cerebral cortex of the cat.

Abstract: Publisher Summary The visual cortex has been shown in both primates and non-primates to include a large number of extrastriate areas in addition to the classically defined visual areas 17, 18 and 19. Not all of these extrastriate areas contain full representations of the visual field, but, whether their maps are partial or complete, the areas abut one another, often with mirror reversals at their borders. As a consequence, the striate and extrastriate areas together form a zone of exclusive visual reponsiveness in the posterior neocortex that is continuous even though having separate areas within it. The arrangement of these visual areas into a continuum has obvious advantages in keeping transcortical association pathways short and also has suggested that the multiple maps might have evolved by a process akin to gene duplication. A visual area has been recently discovered, which appears anomalous in that it lies at a distance from the striate and extrastriate areas, in the anterior part of the cat's cerebral cortex, and yet, like the posterior visual areas, is a zone containing unimodal visually responsive neurons.

Delayed visual maturation in infancy.

Abstract: We describe the clinical and electrodiagnostic features of 8 infants who showed no visual responsiveness and were thought to be severely visually impaired on initial examination. Subsequently all children developed normal visual capabilities and the previously abnormal visually evoked potentials became normal. The clinical and electrodiagnostic features of these infants suggest that they suffered from a widespread cortical maturation delay.