Abstract: Recent research is reviewed and its implications discussed. "On-the-Spot" accident investigations have confirmed that errors of perception by the driver are a major contributory factor to accidents. However, the available evidence suggests that few of these are attributable to reduced or defective vision, since at best only a weak relationship has been found between a driver's level of vision (or visual performance) and his accident rate. A number of reasons for this general finding are considered, including driver compensation. For all drivers, the rapid fall in visual acuity with angular distance from the centre of vision presents particular problems, giving special significance to eye-movement patterns and the problems of visual search. Numerous physical and psychophysical restrictions on visibility could lead to the "looked, but failed to see" type of accident, but their relative importance requires evaluation. There is now much evidence that the driver is quite often operating beyond his visual or perceptual capabilities in a number of key driving situations, including overtaking, joining or crossing a high-speed road, and a number of nighttime situations. It is concluded that "expectancy", based on experience in both the long and the short term, has a profound influence on driver perception and assessment of risk. For all drivers, serious errors of judgment from time to time would seem inevitable. In general, these do not lead to accidents because of, among other things, the safety margins added by the driver and adjustments made by other road users. Thus, despite his limitations and fallibilities, the average driver is involved in surprisingly few serious incidents, particularly in view of the rapid rate of decisionmaking that is required. However, the present accident rate should not be accepted as inevitable and various countermeasures are discussed.

Abstract: It has been proposed that young infants are attentive to quantitative variations in stimulation to the exclusion of qualitative ones. To the extent that this is so, young infants should ignore differences between lights and sounds and should instead respond to auditory and visual stimuli as more or less similar depending on their intensity. To examine this hypothesis, a cardia c habituation/dishabituation method with a test for stimulus generalization was employed . Three-weekold infants were repeatedly presented with white-light followed by white-noise stimuli of different intensities. A U-shaped relationship between magnitude of cardiac response and loudness was found. In view of previous findings that without prior visual stimulation a monotonic increase in cardiac response to the same range of auditory stimuli results, this finding of a significant quadratic relationship with loudness suggests that the infants were responding to the auditory stimuli in terms of their similarity to the previously presented visual stimulus. A separate group of infants presented with a more intense visual stimulus exhibited a shift in the intensity at which a minimal cardiac response occurred. Results of a study with adults did not show any systematic relationship between cardiac response and loudness, indicating that unlike infants, adults do not spontaneously make cross-modal matches of intensity. Our perception of the world is based to a

Abstract: Three experiments are reported which aim to distinguish between mechanisms that might serve joint visual attention between human infants and adults. Between 6 and 18 months of age, the infant will adjust his (or her) line of gaze contingent on a change in the adult's focus of attention but behaves as if the adult is referring to loci within the infants' visual space. Thus, if the adult looks behind the infant, the infant scans the space in front of him. Various explanations of this phenomenon and of the capacity for joint visual attention are discussed.

Abstract: A nonlinear function is derived to describe the contrast transduction process for human visual mechanisms. This function is sigmoid in form, having an accelerating nonlinearity at low contrasts and a compressive nonlinearity at high contrasts. The resulting formulation is consistent with both signal detection theory and with Quick's (1974) equation for probability summation. Similarities between the present description of human vision and properties of complex cells in cat visual cortex are noted.

Abstract: A visual analog of auditory selective attention paradigms is described. Using that analog, we examined the amount of processing required to monitor unattended information. With the materials used, there was no evidence that any processing capacity was required to monitor the unattended information. Memory for the unattended information and the recognition of one’s name were examined to provide additional evidence concerning the fate of the unattended information.

Abstract: Counts of callosal neurons retrogradely labeled by horseradish peroxidase (visualized using multiple substrates) were obtained in areas 17 and 18 of five kittens reared with their eyelids bilaterally sutured and of three kittens which had undergone bilateral enucleation on postnatal days 1–4. These counts were compared with those obtained in normal adult cats. The normal adult distribution of the callosal neurons results from the gradual postnatal reduction of a more widespread juvenile population. Binocular visual deprivation by lid suturing dramatically decreases the final number of callosal neurons and narrows their region of distribution (callosal zone) in areas 17 and 18. A less severe reduction in the final number of callosal neurons is caused by bilateral enucleation, which also increases the width of the callosal zone compared to that of normal cats. Thus, visual experience is necessary for the normal stabilization of juvenile callosal connections. However, since some callosal neurons form connections in the absence of vision, other influences capable of stabilizing juvenile callosal neurons also exist. These influences are probably antagonized by destabilizing influences or inhibited, when the eyes are intact.

Abstract: Three experiments are reported in which the salience of visual stimuli is assessed by finding which of two competing peripheral stimuli elicit a saccade when both are presented simultaneously with the use of paradigm due to Love-Schoen The first experiment shows how salience is affected by position in the visual field A strong effect of retinal eccentricity is found which is compared with the cortical magnification factor Additionally directional biases occur The second experiment shows that temporal change appears to be significant in eliciting a saccade rather than any specific properties related to movement The third experiment shows that contour at high spatial frequencies does not affect salience An area of 4 cycles deg-1 high-contrast square-wave grating possesses the same salience as an equivalent area with identical, constant, space average luminance Taken together, the results suggest that salience might be accountable for in terms of the activation of transient channels in the visual system

Abstract: Human observers detected the global three-dimensional organization of visual patterns consisting of only two successive frames of randomly positioned dots, corresponding to projections of a rotating sphere. A perfectly coherent sphere yielded a stable perceptual organization that was detected more accurately than other slightly less organized patterns.

Abstract: In a visuo-motor pointing task, the accuracy of response was measured in situations which differ in the visual information available and the speed of execution of movement. Results confirm the role of visual cues received from self-produced movement in the control of the trajectory of a limb. Furthermore, it can be shown that a structured visual background is important in the treatment of sensory data concerned with the movement and in target localization. This effect is absent in rapidly executed pointing response.

Abstract: : The visual analysis of surface shape from texture and surface contour is treated within a computational framework. The aim of this study is to determine valid constraints that are sufficient to allow surface orientation and distance (up to a multiplicative constant) to be computed from the image of surface texture and of surface contours. The report is in three parts. Part I consists of a review of major theories of surface perception, a discussion of vision as computation and of the nature in which three-dimensional information is manifest in the image, and a study of the representation of local surface orientation. Part II reconisiders the familiar 'texture gradient'. Part III examines our preception of surface contours. It is shown that surface contours are strong sources of information about local surface shape.

Abstract: A large region of posterior neocortex in a number of species of mammals has been found to be responsive to visual stimuli. In some of these mammals more detailed studies have subdivided the responsive region into separate systematic maps or representations of visual space, and there are several reasons for thinking that these maps are important as functionally distinct subdivisions of the visual system. For instance, it appears that each systematic map is associated with a cortical region having a unique architectonic character and a distinctive pattern of connections with other visual structures. In addition, there is evidence that neurons in separate visual representations differ in the way they respond to visual stimuli. Finally, lesions of different visual maps have produced distinctively different behavior changes.

Abstract: Human observers continue to experience a visual stimulus for some time after the offset that stimulus. The neural activity evoked by a visual stimulus continues for some time after its offset. The information extracted from a visual stimulus continues to be registered in a visual form of memory ('iconic memory') for some time after its offset. We may thus distinguish three distinct senses in which a visual stimulus may be said to persist after its physical offset: there is phenomenological persistence, neural persistence and informational persistence. Various assumptions have been made about the relation between these forms of visual persistence. The most frequent assumption is that they correspond simply to three different methods for studying a single entity. Detailed consideration of what is known about the properties of these three forms of persistence suggests, however, that this assumption is not correct. It can reasonably be proposed that visible persistence is the phenomenological correlate of neural persistence occurring at various stages of the visual system: photoreceptors, ganglion cells and the stereopsis system. Iconic memory on the other hand, does not correspond to visible persistence, nor to neural persistence in any stage of the visual system. Recent work, in fact, suggests that iconic memory is a property of some relatively late stage in the visual information-processing system, rather than being a peripheral sensory buffer store. This suggestion raises some fundamental theoretical issues concerning the psychology of visual perception, issues with which cognitive psychology has yet to come to grips.

Abstract: Many visual phenomena, in particular, visual discrimination performance as a function of light intensity, have been attributed to a, nonlinearity in the retinal stages of the visual system. A comprehensive analytical quantified derivation of the nonlinearity based upon an optimum processor approach to visual perception is presented. The account follows optimum decision rules described by likelihood ratio tests applied to Poisson processes. The processor is constrained in ways inferred from empirical phenomena, particularly visual discrimination performance. A nonlinearity of the type y(x) = [log (x)]2, x 1, is mathematically derived applying rigorous engineering principles from statistical communications and signal detection theory. It is shown that this nonlinearity is in full conformity with known visual performance and the ideal detection hypothesis. The results are then confronted with actual physiological data to fimd a visual-system mechanistic correlate.

Abstract: In the normal cat, most cells in area 17 can be binocularly driven. Sectioning the corpus callosum results in a significant reduction in binocularly driven cells. Normal binocular vision is thus dependent on the corpus callosum.

Abstract: Children of ages 3, 3Vi, and Wi years were tested for a previously unstudied form of knowledge about visual perception, namely, that an observer stationed closer to a small object will be able to see it better than an observer stationed farther away on roughly the same line of sight, whereas they will be able to see it equally well if stationed side by side at the same distance from it. The data suggest that this knowledge undergoes considerable development during the preschool period, with many 4Vi-year-olds seemingly possessing it in the form of a general rule.

Abstract: Although geometric information is altered when a picture’s viewing point is changed, such changes often do not affect perception. Two experiments assessed pictorial perception relative to the distortions introduced by viewing point dislocation. Results provide a psychophysical demonstration of pictorial compensation and suggest that it is based on the discrepancy between the actual and an assumed-correct viewing position. An explanation of pictorial compensation is offered that could be applied to direct picture perception and to picture-in-a-picture perception.

Abstract: Visual discrimination was studied in each visual field of a patient with surgical section of the posterior corpus callosum. Light-detection thresholds were increased nearly equally in right and left visual fields, suggesting that normal thresholds require the cooperative activity of both posterior cerebral hemispheres, mediated by the corpus callosum. In contrast, there was superiority in the right visual field in naming, coping, and matching letter, number, and colors, but not unfamiliar shapes. The results are attributed to a differential effect of experience on perception in each visual field. The right-visual-field superiority in learning to perceive arrays on letters, numbers, and colors may result directly from the superiority of the left hemisphere in speech.

Abstract: Two experiments were conducted to test theories of the stimulus-response (S-R) compatibility effect. Stimuli presented above and below a fixation point in the left and right visual field signaled choice responses in the midsagittal plane. Even though the duration of stimulus presentation in Experiment 1 was sufficiently brief, such that the possibility of eye movements was precluded, a visual half-field S-R compatibility effect was still obtained. That such an effect is found when it can be adequately specified to which hemisphere stimulus information is presented suggests that an explanation in terms of cerebral laterality factors be considered. The second experiment employed arbitrary symbols to represent the spatial property of stimuli used in prior experiments, and a similar pattern of results was obtained. These results are discussed in terms of a functional view of cerebral organization.

Abstract: : In many everyday situations relative motion exists between human beings and the visual information which they must acquire and resolve in order to perform their tasks successfully. In particular, tasks, such as flying aircraft, driving automobiles and other vehicles, and resolving moving information presented via visual displays, impose a requirement on the human operator to process moving information. Since Dynamic Visual Acuity (DVA) is a critical visual skill involved in performing such visual tasks, the present review was undertaken in order to better understand the visual skill and to provide a basis for continuing research in this area. (Author)