Showing papers on "Visual perception published in 1975"

Visual Following and Pattern Discrimination of Face-like Stimuli by Newborn Infants

Abstract: Forty newborn infants, median age 9 minutes, turned their eyes and heads to follow a series of moving stimuli. Responsiveness was significantly greater to a proper face pattern than to either of two scrambled versions of the same stimulus or to a blank. The demonstration of such consistent response differences suggests that visual discriminations are being made at this early age. These results imply that organized visual perception is an unlearned capacity of the human organism. The preference for the proper face stimulus by infants who had not seen a real face prior to testing suggests that an unlearned or "evolved" responsiveness to faces may be present in human neonates.

Visual motion perception.

Abstract: In this article the author uses projective relations as the theoretical foundation of his investigations of visual space and motion. Several laboratory experiments involving perceptual vector analysis and its geometric basis are described. In most of the experiments the visual stimuli consisted of computer-controlled patterns displayed on a televisionlike screen and projected into the eyes of subjects by means of a collimating device that removed parallax as well as the possibility of seeing the screen. A common characteristics of the experiments was that the observer was evidently not free to choose between a Euclidean interpretation of the changing geometry of the figure in the display and a projective interpretation. For example, the observer could not persuade himself that what he was seeing was simply a square growing larger and smaller in the same visual plane; his visual system insisted on telling him that he was seeing a square of constant size approaching and receding. Hence he perceived rigid motion in depth, rotation in a specific slant, bending in depth and so on, paired with the highest possible degree of object constancy. Further experiments were conducted to determine if the principles of perceptual analysis hold true for the more complex paterns of motions encountered in everyday life. These experiments led to the conclusion that during locomotion the components of the human visual environment are interpreted as rigid structures in relative motion.

Innate and environmental factors in the development of the kitten's visual cortex.

Abstract: 1. This is a study of the receptive fields of 771 cells recorded in the visual cortex of twenty-five kittens reared normally or subjected to various kinds of visual deprivation or environmental manipulation. 2. Kittens deprived of patterned visual experience, by dark rearing or diffuse occlusion of the eyes, have a majority of cirtical neurones with little or no specificity for the orientation or axis of movement of visual stimuli. However, in such deprived animals, especially those younger than 3 weeks, there are a number of genuinely orientation selective cells. They are broadly "turned" (by adult standards), they are almost always of the simple type, are heavily dominated by one eye, and are found mainly in the deeper layers of the cortex, especially layer IV. 3...

Contrast constancy: deblurring in human vision by spatial frequency channels.

Abstract: The perception of contrast was measured in humans by a technique of subjective contrast-matching, and was compared with contrast sensitivity as defined by threshold measures. 2. Contrast-matching between different spatial frequencies was performed correctly (especially at frequencies above 5 c/deg) despite the attenuation by optical and neural factors which cause large differences in contrast thresholds. 3. Contrast-matching between single lines of different widths was also veridical, and was not limited by the spatial integration (Ricco's Law) present at threshold. Adaptation to gratings altered the appearance of lines, and this could be best understood in Fourier terms. 4. The generality of these results was shown by matching the contrast of pictures which had been filtered so that each contained a one octave band of spatial frequencies. 5. Within the limits imposed by threshold and resolution, contrast-matching was largely independent of luminance and position on the retina. 6. Six out of eleven astigmatic observers showed considerable suprathreshold compensation for their orientation-specific neural deficit in contrast sensitivity. 7. These results define a new property of vision: contrast constancy. It is argued that spatial frequency channels in the visual cortex are organized to compensate for earlier attenuation. This achieves a dramatic 'deblurring' of the image, and optimizes the clarity of vision.

Perception of linear horizontal self-motion induced by peripheral vision (linearvection) basic characteristics and visual-vestibular interactions.

Abstract: The basic characteristics of the sensation of linear horizontal motion have been studied. Objective linear motion was induced by means of a moving cart. Visually induced linear motion perception (linearvection) was obtained by projection of moving images at the periphery of the visual field. Image velocity and luminance thresholds for the appearance of linearvection have been measured and are in the range of those for image motion detection (without sensation of self motion) by the visual system. Latencies of onset are around 1 sec and short term adaptation has been shown. The dynamic range of the visual analyser as judged by frequency analysis is lower than for the vestibular analyser. Conflicting situations in which visual cues contradict vestibular and other proprioceptive cues show, in the case of linearvection a dominance of vision which supports the idea of an essential although not independent role of vision in self motion perception.

Differential hemispheric mediation of nonverbal visual stimuli

Abstract: Studies employing schematic faces of three features explored the role of the left hemisphere as an analytic processor in difficult discriminations and the role of the right hemisphere in easy gestalt matches. In a discrimination task, the successively presented members of a stimulus pair differed in all three features. When both stimuli went to the same visual field there was a Visual Field X Judgments interaction; judgments same were processed faster in the left visual field. When a test stimulus differing on all three features from a previously memorized target face was matched to the latter, both judgments same and different were made faster for stimuli in the left visual field. However, when the test stimulus and the memory items differed on only one feature the right field proved superior for both judgments same and different. Language: en

Auditory-visual perception of speech.

Abstract: Hearing-impaired persons usually perceive speech by watching the face of the talker while listening through a hearing aid. Normal-hearing persons also tend to rely on visual cues, especially when they communicate in noisy or reverberant environments. Numerous clinical and laboratory studies on the auditory-visual performance of normal-hearing and hearing-impaired children and adults demonstrate that combined auditory-visual perception is superior to perception through either audition or vision alone. This paper reviews these studies and provides a rationale for routine evaluation of auditory-visual speech perception in audiology clinics.

Visual experience and cortical development.

Abstract: The past twelve years have been exciting for those interested in the classical question, “How much do our visual capacities depend on innate developmental factors, how much on the moulding effects of visual experience?” Recent papers1–4 have settled some issues, but may start new waves of controversy, and this is the occasion for writing this review.

A comparison and elaboration of two models of metacontrast.

Abstract: Metacontrast has been the subject of two neural network simulations by Weisstein and Bridgeman. We compare and elaborate on the two models, correct flaws not inherent in the models' conceptualizations, and discuss the remaining shortcomings. The idea behind how U-shaped metacontrast functions are generated is similar in both models, but the assumptions about how the visual system is organized are quite different. In one of the models temporal ringing, combined with a complex and implausible linking hypothesis, is necessary in order for masking to be obtained; this model assumes a single spatial and temporal channel. In the other model, masking does not depend on temporal ringing; this model assumes multiple spatial and temporal channels and a simple linking hypothesis. We show that of the two models only the second adequately predicts empirical metacontrast functions, and we relate this model to recent evidence that the visual system contains multiple channels. Sometimes treated as a puzzling and somewhat singular phenomenon, isolated from the \"mainstream\" of visual data and theory, metacontrast may, on the contrary, turn out to be one of the more interesting manifestations of a multiple-channel visual system.

Visual attention to size and number of pattern details by term and preterm infants during the first six months.

Abstract: 2 dimensions inversely varied in previous complexity studies using checker-boards were varied independently. Patterns with more elements, angles, and information as well as patterns with larger elements received longer fixation at all ages, but initially prepotent size preferences decreased with age while number preferences became stronger. Further analysis showed the inadequency of contour length as the stimulus determinant for, or of increasing "optimal complexity" with age as the interpretation of, these previous findings. Term-preterm comparisons at 5-week intervals proved changes were a function of prenatal plus postnatal development rather than age from birth alone.

Eye movements and visual perception: A “two visual system” model*

Abstract: Eye movement is one of the few externally measurable activities of visual perception, and provides a checkpoint for models of perceptual processes. Here the model of Arbib & Didday (1971) is compared with that of Noton & Stark (1970, 1971 a , b ), and is found to predict the same behavior but without requiring explicit storage of eye movement commands.

The Relationship of Selected Visual- Perceptual Abilities to School Learning

Abstract: DONALD D. HAMMILL, Ed.D. Austin, Texas The relationship between certain visualperceptual abilities and school learning has long been a source of interest to educators, many of whom have speculated that deficits in visual perception may cause or, at least, contribute to academic failure. Historically, this assumption has been based upon the clinical experience of various members of the educational community as well as upon some basic research (Barrett, 1965; Bryan, 1964; Frostig & Maslow, 1969; Goins, 1958; Kephart, 1971; Pitcher-Baker, 1973; Rosen, 1966; Wepman, 1964). While visual perception and, in particular, its relationship to school learning have received much attention in professional journals, the educational usefulness of this important theoretical construct has never been fully substantiated. In fact, recent opinion and research have seriously questioned its relevance as a practical correlate of learning failure (Cohen, 1969; Hammill, 1972; Mann, 1970). It is important to note, however, that many school systems throughout the country are still committing large numbers of man hours

Visual spatial summation in two classes of geniculate cells

Abstract: VISUAL perception can be viewed as a transformation and a distortion of the spatial patterns which exist in the outside world. The transformation of external objects into neural images is accomplished by the summation of excitatory and inhibitory influences over the visual field of each neurone. Distortion occurs when the neural response is not simply proportional to the sum of excitation and inhibition because of nonlinear mechanisms in spatial summation. If the responses of all visual cells were distorted by such nonlinear summation, fine visual discriminations like those necessary for reading Nature would be impossible. Nonlinear mechanisms do however, seem to be important in one class of visual neurone, perhaps for signalling change or motion in the external world. We have attempted to understand the importance of the different kinds of spatial summation by studying single cells in the cat visual system.

The Aubert-Fleischl phenomenon: a temporal frequency effect on perceived velocity in afferent motion perception.

Abstract: Apparent velocities of moving visual stimuli are known to be different depending on whether the subject pursues the stimulus (efferently controlled motion perception) or whether the eye is stationary and the image moves across the retina (afferent motion perception). Afferent motion perception of a periodic pattern or a moving single object causes overestimation of velocity (magnitude estimations) as compared to smooth pursuit. This socalled Aubert-Fleischl phenomenon is shown to depend on local temporal frequency stimulation on the retina caused by the repetitive passage of contrast borders of the moving periodic pattern. This is evidenced by the fact that for a given stimulus speed the amount of overestimation is a function of the spatial frequency of the pattern (or the angular subtend of a single moving object) and that the Aubert-Fleischl phenomenon is not observed if a single edge moves. Background characteristics seem not to influence the apparent velocity during smooth pursuit.

Newborn Infant Attention to Form of Contour.

Abstract: Human neonates selectively fixated patterns with curved rather than straight contours when the outermost contours differed in this form variable and when quantitative variables were controlled. The presence from birth of a discrimination ability basic to later form perception was evidenced.

Spatial perception in the blind.

Abstract: It is often that the spatial senses (vision, hearing and the tactual senses) operate as distinct and independent modalities and, moreover, that vision is crucial to the development of spatial abilities. However, well controlled studies of blind persons with adequate experience show that they can function usefully in space. In other words, vision is not a necessary condition for spatial awareness. On the other hand, thought the blind may be equal or even superior to the sighted when performing spatial tasks within the body space, they may be deficient, either developmentally or absolutely, in tasks which involve events at a distance from the body, principally in auditory localization. One possible explanation of the differences between blind and sighted (McKinney, 1964; Attneave & Benson, 1969, Warren, 1970) is that vision is the primary spatial reference, and inputs from other modalities are fitted to a visual map. Several criticisms of this theory are adduced and an alternative theory derived from Sherrington (1947), in which all sensory inputs map on to efferent patterns, is sketched.