Abstract: The effect of temporal discontinuity on visual search was assessed by presenting a display in which one item had an abrupt onset, while other items were introduced by gradually removing line segments that camouflaged them. We hypothesized that an abrupt onset in a visual display would capture visual attention, giving this item a processing advantage over items lacking an abrupt leading edge. This prediction was confirmed in Experiment 1. We designed a second experiment to ensure that this finding was due to attentional factors rather than to sensory or perceptual ones. Experiment 3 replicated Experiment 1 and demonstrated that the procedure used to avoid abrupt onset--camouflage removal--did not require a gradual waveform. Implications of these findings for theories of attention are discussed.

Abstract: Infants' abilities to detect auditory-visual correspondences for speech were tested in two experiments. Infants were shown two visual images side-by-side of a talker articulating, in synchrony, two different vowel sounds, while a sound matching one of the two vowels was auditorially presented. Infants' visual fixations to the two faces were video-recorded and scored by an independent observer who could neither see the faces nor hear the sounds. The results of Experiment 1 showed that the auditory stimulus systematically influenced infants' visual fixations. In- fants looked longer at the face that matched the sound. In Experiment 2, the same visual stimuli were presented, but the auditory stimuli were altered so as to remove the spectral information contained in the vowels while preserving their temporal characteristics. Performance fell to chance. Taken together, the experiments suggest that infants recognize the correspondences between speech information presented auditorially and visually, and moreover, that this correspondence is based on the spectral information contained in the speech sounds. This suggests that infants represent speech information intermodally.

Abstract: The results of a cognitive experimental analysis of the reading functions of four developmentally dyslexic subjects are presented. Data are considered on an individual basis in an attempt to specify the primary source of disturbance in each case, and the manner in which the normal course of reading development has been distorted. Subject RO showed an effect on the analytic functioning of the visual processor, which affected speed of non-word reading, but appeared not to have prevented the construction of a normal visual word recognition system. In subject LT a phonological impairment was implicated, and this was associated with a pattern of performance similar to that of adult phonological dyslexics. Subjects GS and SE gave evidence of serial letter-by-letter reading (impaired wholistic function of the visual processor), which produced a pattern not unlike that of adult surface dyslexics (effects of spelling regularity, regularisation errors). The manner in which these impairments might disrupt t...

Abstract: Department of Neuroscience Albert Einstein College of Medicine Bronx, New York 10461 Department of Psychiatry Veterans Administration Hospital Palo Alto, California 94305 ‘Institute for Perception Soesterberg, the Netherlands dDepartment of Psychology University of North Carolina Greensboro, North Carolina 2741 2 Department of Neurosciences University of California San Diego, California 92093 /Department of Psychology University of Helsinki 00170 Helsinki 17. Finland gDepartment of Neurology University of California Irvine, California 92668 Hospital de la Salpetriere F-75634 Paris, Cedex 13, France ‘ Nebraska Psychiatric Institute Omaha, Nebraska 68106 RISTO NAATANEN! JOHN POLICH: BERNARD

Abstract: Preschool children's evaluation and integration of visual and auditory information in speech perception was compared with that of adults. Subjects identified speech events, which consisted of synthetic speech syllables ranging from /ba/ to /da/ combined with a videotaped /ba/, /da/, or no articulation. Both variables influenced the identification judgments for both groups of subjects. The results were used to test current views of the development of perceptual categorization and speech perception. Tests of quantitative models indicated that both preschool children and adults had available continuous and independent sources of information. The results were well described by a fuzzy logical model of perception, which assumes that the perceiver integrates continuous and independent sources of information and determines the relative goodness of match to prototype definitions in memory. The only developmental difference was less of an influence of the visual source of information for children relative to adults. 1 explanation is that the children simply attended less to the visual source. A second experiment eliminated the attentional explanation by showing identical results when the children were also required to indicate whether or not the speaker's mouth was moving.

Abstract: From the Publisher: Computer scientists designing machine vision systems, psychologists working in visual perception, visual neurophysiologists, and theoretical biologists will derive a deeper understanding of visual function - in particular the computations that the human visual system uses to analyze motion-from the important research reported in this book. The organization of movement in the changing image that reaches the eye provides our visual system with a valuable source of information for analyzing the structure of our surroundings. This book examines the measurement of this movement and the use of relative movement to locate the boundaries of physical objects in the environment. It investigates the nature of the computations that are necessary to perform this analysis by any vision system, biological or artificial. The author first defines the goals of these visual tasks, reveals the properties of the physical world that a vision system can rely upon to achieve such goals, and suggests general methods that can be used to carry out the tasks. From the general methods, she designs algorithms specifying a particular sequence of computations that a vision system can execute to perform these visual tasks. These algorithms are implemented on a computer system under a variety of circumstances. Combined with the traditional approaches of psychology and neurophysiology, this computational approach provides an exciting analysis of visual function, raising many new questions about the human vision system for further investigation. Ellen Catherine Hildreth received her doctorate from MIT. She is a Research Scientist in the MIT Artificial Intelligence Laboratory and associate director of theCenter for Biological Information Processing at the Whitaker College of Health Sciences, Technology, and Management. The Measurement of Visual Motion is an ACM Distinguished Dissertation.

Abstract: This study addresses the question of how simple networks can account for a variety of phenomena associated with the shift of a specialized processing focus across the visual scene. We address in particular aspects of the dichotomy between the preattentive-parallel and the attentive-serial modes of visual perception and their hypothetical neuronal implementations. Specifically, we propose the following: (1) A number of elementary features, such as color, orientation, direction of movement, disparity etc. are represented in parallel in different topographical maps, called the early representation. (2) There exists a selective mapping from this early representation into a more central representation, such that at any instant the central representation contains the properties of only a single location in the visual scene, the {\it selected} location. (3) We discuss some selection rules that determine which location will be mapped into the central representation. The major rule, using the saliency or conspicuity of locations in the early representation, is implemented using a so-called Winner-Take-All network. A hierarchical pyramid--like architecture is proposed for this network. We suggest possible implementations in neuronal hardware, including a possible role for the extensive back-projection form the cortex to the LGN.

Abstract: Four experiments are described in which the newborn's ability to habituate to a visual stimulus and subsequently to display novelty/familiarity preferences was explored. The same two types of stimuli, simple geometric shapes and complex colored patterns, were used throughout. The results suggest that newborns will reliably give novelty preferences when an infant-controlled habituation procedure is used. However, no reliable preferences emerged following either a brief exposure to a stimulus, or when novel and familiar stimuli were presented paired together over several trials. In experiment 4 different, novel stimuli were presented on successive infant-controlled trials and the decline in trial length observed during habituation trials was not found. Although this is further evidence that habituation to a repeated visual stimulus does occur in the newborn, half of the subjects in experiment 4 would have met the infant-controlled criterion of habituation: these results are discussed in terms of artifacts that can affect habituation. While there is considerable intra-and intersubject variability in trial duration, and in other dependent measures, the results give support to the model of habituation which assumes it to be an exponentially decreasing process.

Abstract: Visual evoked potentials (VEPs) can be used in a multitude of ways to assess the various levels of visual processing. The human visual system consists of multiple, parallel channels which process different information, and each channel constitutes a set of sequential processes. An algorithm of sequential steps that can be used to assess visual function is reviewed. The pathophysiology of retinal, anterior visual pathways and retrochiasmal pathways can be objectively evaluated by VEPs.

Abstract: Cross-modal influences on perceptual organization were demonstrated using a display that combined a stimulus for auditory stream segregation with its visual apparent movement analogue. Both phenomena give rise to the perception of either one or two objects, depending on the rate of presentation of the stimuli. At slower rates, one object is perceived, while two are perceived at faster rates. Subjects indicated the stimulus onset asynchrony (SOA) between successive stimuli at which the perceptual shift occurred in each modality. Then visual and auditory stimuli were presented concurrently and subjects responded to the “target” modality sequence. Two intergroup separations for the nontarget stimuli were used. Distances were chosen, based on the subject’s calibration data, which represented one and two objects, respectively, at the stream segregation point for the target sequence. Segregation occurred at larger SOAs when the nontarget stimulation indicated two objects than when it represented one. This was true for both visual and auditory target sequences.

Abstract: The present study examined whether younger observers (kindergartners, second graders, and fourth graders) could extract relative weight information from collisions and also lifting events, and if they could judge whether collisions were natural (i.e., momentum conserving) or anomalous (non-momentum conserving). 20 children at each age and 20 adults viewed videotapes of 8 collisions (4 natural, 4 anomalous) and 6 sequences of lifting events. Observers also viewed sequences of static images taken from these events. Observers at all grade levels were able to reliably judge relative weight in both collisions and lifting events, and could differentiate between natural and anomalous collisions. Performance was much poorer when static sequences of the events were viewed, especially for the young children. A consistent age trend was noted across tasks: adults performed better than second and fourth graders who, in turn, performed better than kindergartners. In addition, there was evidence that younger children were differentially aided when the kinematics of the event made the kinetics more pronounced.

Abstract: Visual evoked potentials (VEPs) to lateralized light flashes were recorded from the parietal midline, and from homologous occipital and central sites, in a GO/ NOGO reaction time task. The N160 component of the VEP was found to be larger over the hemisphere contralateral to the visual field of stimulus exposure at all pairs of lateral electrodes. At the occipital sites only, N160 latency was also shorter from the contralateral hemisphere, by an average of approximately 14 msec. This was not so centrally, where a non-significant value of approximately 4 msec was obtained. These data are considered to be consistent with Milner and Lines' hypothesis that callosal transmission occurs at different rates in different functional regions of the corpus callosum.

Abstract: It has been proposed that the human visual system prefers perceptions of objects that are rigid or undergo minimum form change. A counterexample is presented in which a rigid two-dimensional figure rotating in the frontal plane is perceived as a distorting three-dimensional shape. It is argued that this perception results from the stimulation of automatic processes for perceiving size change, and that these processes are not subject to a general rigidity assumption.

Abstract: A patient who suffered traumatic hematomas of both occipitotemporal regions, but who had normal visual acuity, language, and cognitive functions, could not recognize faces of family members, celebrities , or recent acquaintances (prosopagnosia). He could distinguish same from different faces when they were presented simultaneously, but could not recognize faces that had been presented to him 90 seconds earlier. He could read and name objects correctly, but could not recognize any previously viewed object if it was reexamined later with other objects of the same semantic class. He had no difficulty copying complex figures, but synthesized incomplete visual information poorly and pursued an abnormal visual search strategy. We suggest that prosopagnosia is part of a more general inability to distinguish among objects within a visual semantic class. It results from impaired visual memory and perception caused by visual association cortex damage and interruption of the inferior longitudinal fasciculus connecting visual association cortex and temporal lobe.

Abstract: Visual training continues to be used as a remediation technique for reading disabilities despite consistent evidence that it does not provide effective treatment. A review of the ophthalmologic, optometric, and psychological literature relating to the assumption that a relationship exists between reading failure and perceptual ability has found no evidence to support this assumption.

Abstract: : We argue that one of the early goals of color vision is to distinguish one kind of material from another. Accordingly, we show that when a pair of image regions is such that one region has greater intensity at one wavelength than at another wavelength, and the second region has the opposite property, then the two regions are likely to have arisen from distinct materials in the scene. We call this material change circumstance the 'opposite slope sign condition.' With this criterion as a foundation, we construct a representation of spectral information that facilitates the recognition of material changes. Our theory has implications for both psychology and neurophysiology. In particular, Hering's notion of opponent colors and psychologically unique primaries, and Land's results in two-color projection can be interpreted as different aspects of the visual system's goal of categorizing materials. Also, the theory provides two basic interpretations of the function of double-opponent color cells described by neurophysiologists. Keywords include: Image understanding; Vision; Color vision; Color theory.

Abstract: One of the most confused and confusing concepts wi th in the optometric and educational fields is the difference between visual perception and visual funct ion. Unfor tunate ly , many professionals use these terms interchangeably. As a result, perception and function are considered to be semantically dif ferent, yet conceptually the same. This situation does not exist solely in miscommunication between optometrists and educators. It can be exacerbated by optometrists themselves, who have failed to arrive at some consensus wi th in their own f ie ld regarding this issue. Optometrists w h o value the function model , are commit ted to such attributes o f vision as binocularity, or the teaming and coordination o f the two eyes, accommodat ion, or the abil ity to change and sustain focus, and accurate tracking, or precise saccadic and pursuit eye movements without motor overflow. M a n y o f these optometrists also assess perception, and this is where the confusion begins. T h e assumption is that visual function as described above, is automatically l inked to visual perception, which is most often measured by some form of paper and pencil task. A l s o , w i th the exception o f a block design type task, visual perception testing is always two-d imensional . Visual perception, as a hypothetical construct, is best known through the f ie ld o f learning disabilities. A simplistic explanation expressed through education is that visual perception occurs wi th in the brain, and i M h e process of attributing meaning to visual st imul i . I t is most often described in various professional literature as having to do wi th recognit ion, discrimination, par t -who le relationships, f igure-ground, form constancy, and spatial relationships. Visual perception is also often tied to motor performance in the form of eye-hand coordination tasks. Given this perspective, it is easy to understand how function and perception can become so closely aligned and even interchangeable. I t would appear that the nature o f eye function would have direct impact on the nature of how the brain perceives. Yet this is not necessarily the case. Cl in ica l optometric experience and evaluation, and formal perceptual test data ( V i s u a l M o t o r In tegrat ion Test , M o t o r F r e e Visual Perception Test, Ra ven's, Southern Cal i fornia Figure Ground Test, Detroit Visual Attent ion for Letters and Disarranged Pictures, M o n e y Road M a p Test ) , lead to the conclusion that there are four groups o f chi ldren. The first group has function problems and perceptual problems. This is the group that most serves to confuse the issue. W h e n optometric training is accomplished, perceptual qualities improve and the relationship seems f i rmly established. Group two has function problems without any visual perceptual diff icult ies. Group three has perceptual disorders without vision function problems, which can be explained away by the suggestion that visual function is only one factor in the development o f perceptual processing. Final ly , group four has function and perception problems, but successful optometric treatment for function does not result in a definit ive change in percept ion. This can also be explained by the mult i factor v iewpoint . Group two and group four certainly mitigate against any dogmatic position concerning the direct, inexorable relationship between function problems and perceptual deficits. This analysis might also serve to demonstrate the need for a definite distinction to be made between function and perception. Furthermore, optometrists w h o test for both, use entirely different tests in each area. Optometrists do not test perception in order to diagnose functional disorders. They may use this approach to look for potential candidates for subgroup one. O f course, they can only know this, ex post facto. Vis ion training is successful and perception improves. T h e missing l ink , i f there is such a th ing, may be attention and efficiency and f reedom f r o m fatigue. A l though it is not easily measured, the chi ld 's abil ity to direct and sustain visual attention seems to be improved through successful vision t r a i n i n g for f u n c t i o n a l d e f i c i e n c i e s . Teachers, parents, and the children themselves are the usual contributors o f this information. T h e abil i ty to visually attend for longer periods o f t ime would certainly indicate a decreased influence of fatigue. A l s o , there is an implication that the ef f ic iency o f the visual system during attention to task has been enhanced and disruptive symptoms (blurred vision, double vision) have been e l imi nated.

Abstract: Anhedonia, an inability to experience pleasure, is a personality characteristic often noted in psychiatric patients, particularly depressives and schizophrenics. Furthermore, it has been proposed as a central and enduring trait of schizotypic individuals, who are believed to be at risk for becoming schizophrenic (Meehl, 1962). Following the development of a self-report questionnaire assessing anhedonia (Chapman et al., 1976), Chapman and colleagues have reported a number of interview, psychometric, and behavioral studies of psychotic-like characteristics in anhedonics selected from a variety of populations. The present paper summarizes a series of studies that demonstrate P300 and negative slow wave deficits in anhedonic subjects consistent with similar deficits reported in schizophrenics (reviewed by Roth, 1977).

Abstract: : A difficult problem in vision research is specifying how meaningful objects are recognized using the visual feature information extracted from an image The fundamental issue involves the interaction of different levels of representation of visual information The technical and theoretical problems that must be addressed in specifying this interaction arise in any attempt to model visual object perception We attempt to deal with some difficult aspects of this process within the context of Feldman's Four Frames model of visual perception The model consists of four continually interacting representational frames, expressed in terms of a massively parallel, connectionist formalism Within the Four Frames model, the problem of accessing object representations using visual feature information can be defined in specific computational terms This paper presents the detailed design of a connectionist model as a possible solution to some of the major problems in the visual recognition of objects The model proposes that an object is represented as a hierarchical structure of geometric subparts Recognition proceeds by determining in parallel that all subparts of an object are present in the image, and then sequentially verifying that each subpart is in the proper spatial relation to the others Implementation results demonstrate that the model can recognize any of a set of simple objects given fairly general feature input Although the model is developed in the context of a drastically simplified visual domain, the principles it embodies are argued to adhere to many of the behavioral and biological constraints of real-world vision

Abstract: Two aspects of the information processing involved in word recognition—encoding and memory search—were investigated in learning-disabled children. A short-term memory recognition paradigm was employed which allowed for the separation of reaction time into separate processing stages. Subjects were 16 learning-disabled children with particular deficiencies in word recognition and 16 control children equated for age, grade and intelligence. Input modalities of both stimulus array words to be encoded and stored in short-term memory, and target words for recognition were manipulated, resulting in three experimental conditions: (1) Visual/Visual, (2) Auditory/Auditory and (3) Auditory/Visual. Three hypotheses were tested each involving inferences about internal operations based en reaction time. While LD subjects did not differ from control subjects at the encoding stage of word recognition, LD subjects required significantly more processing time for memory search.