The effect of widening longitudinal road markings on driving speed perception

Road markings may influence driver behavior, and therefore road safety. An increase in the width of road markings might lead drivers to perceive lanes to be narrower than they really are, creating the illusion of traveling faster. The objective of this paper is to analyze whether wider longitudinal road markings can affect the perception of lane width and thus induce drivers to slow down. To this end, three curves with reduced visibility were selected for a field experiment. The road markings were painted wider than normal, and video recordings were made with narrow and wide markings by a camera installed in a vehicle. A total of 14 videos were shown to each of the 185 participants; then a survey was carried out to analyze in which video the participants perceived higher speed. The results showed that if the participants perceived differences in speed, the higher speed was perceived with the wide markings. This perception of higher speed increased if the participant was female, or if the participant had ever had an accident. In view of the obtained results, it can be said that the use of wider road markings could help reduce vehicle speed, thus contributing to improved road safety.     

Visual perception of collinearity

In a metrical space, there exists an intimate relation between collinearity and parallelity. In particular, in a Riemannian space collinearity is just a special case of parallelity. Is this true for visual space as well? We investigated the visual perception of collinearity by having subjects align two bars in the horizontal plane at eye height. The distances of the bars from the subject and the angles at which they were placed were varied. We found deviations of up to 22 degrees. The deviations of the left and right bars could be split into two independent components: namely, the sum and the difference of the deviations of the left and right bars. We found that the former depended only on the ratio between the distances of each bar from the subject, whereas the latter was largely independent of the positions of the bars. The difference in deviations corresponded to the deviation from parallelity. Compared with the results in the parallelity task (Cuijpers, Kappers, & Koenderink, 2000b), the deviations from parallel were much smaller. As a consequence, the results of the two experiments cannot be described by the same Riemannian geometry. This indicates that the intrinsic geometry of visual space differs across tasks. This is conceivable if the intrinsic geometry of visual space is operationally defined.     

Visual perception of surface wrinkles

To study the relationship between visual perception of magnitude of wrinkles and geometrical parameters of surfaces, four potentially relevant parameters of the surface profile were considered: the variance (sigma2), the cutting frequency (Fc), the effective disparity curvature (Dce) of the wrinkled surface over the eyeball distance of the observer, and the frequency component of the disparity curvature (Dcf). Analysis of garment seams with varying amount of pucker showed that, while the logarithm for each of these four parameters has a strong linear relationship with the visually perceived magnitude of wrinkles, following the Fechner Law, the effective disparity curvature (Dce) and the frequency component of the disparity curvature (Dcf) with visual perception appeared stronger. This modeling may be an objective method for measuring magnitude of surface wrinkles.     

Visual perception in 'low vision'

'Low vision' has an international classification as an impairment of vision that is defined by loss of visual acuity and the size of the visual field. Functional classification that would depict capability to use vision in different activities has not yet been agreed upon. Abnormal visual information leads to changes in visual perception, and brain-damage-related visual impairment may alter or prevent one or several cognitive visual functions. Abnormal visual perception opens a window into brain mechanisms that the psychophysicists otherwise do not have. Together with clinicians, psychophysicists can help visually impaired persons to understand the nature of their disability by thoroughly studying the nature of the altered image and the profile of cognitive visual functions.     

Visual perception and aging.

A series of studies performed in our laboratory on aging and its effect on perceptual processing and working memory capacity for visual stimuli are reviewed. Specifically, studies on luminance, colour, motion, texture, and symmetry processing are reported. Furthermore, experiments on the capacity to retain size and spatial frequency information are also discussed. The general conclusion is that there are a number of perceptual abilities that diminish with age. However, the extent of these deficits will depend on the complexity of the neural circuitry involved for processing a given task. This is also true for visual working memory where no evidence of loss due to aging is demonstrated for processing low-level visual information, when individual differences in sensory input are compensated for. It is concluded that perceptual processing deficits due to aging (like working memory) will become evident when the computational load reaches a certain level of complexity (larger or more complex network) even if the tasks remain cognitively simple.     

Visual factors in word perception

An experiment is reported confirming the existence of the “word-letter phenomenon” (WLP): At tachistoscopic exposure durations, each letter of a four-letter word is perceived more accurately than a single letter. Data obtained rule out several artifactual interpretations, including the possibility that perception of letters in a word is facilitated merely by the presence of adjacent contours. The WLP is shown to depend critically on what type of display is used as a preand postexposure field. While a masking field of high-contrast random contours produced a large and reliable WLP, a plain white field eliminated the phenomenon entirely. This pattern of results suggests several ways in which perception at the word level may differ from perception at the letter level.     

Visual perception and corollary discharge

Perception depends not only on sensory input but also on the state of the brain receiving that input. A classic example is perception of a stable visual world in spite of the saccadic eye movements that shift the images on the retina. A long-standing hypothesis is that the brain compensates for the disruption of visual input by using advance knowledge of the impending saccade, an internally generated corollary discharge. One possible neuronal mechanism for this compensation has been previously identified in parietal and frontal cortex of monkeys, but the origin of the necessary corollary discharge remained unknown. Here, we consider recent experiments that identified a pathway for a corollary discharge for saccades that extends from the superior colliculus in the midbrain to the frontal eye fields in the cerebral cortex with a relay in the medial dorsal nucleus of the thalamus. We first review the nature of the evidence used to identify a corollary discharge signal in the complexity of the primate brain and show its use for guiding a rapid sequence of eye movements. We then consider two experiments that show this same corollary signal may provide the input to the frontal cortex neurons that alters their activity with saccades in ways that could compensate for the displacements in the visual input produced by saccadic eye movements. The first experiment shows that the corollary discharge signal is spatially and temporally appropriate to produce the alterations in the frontal-cortex neurons. The second shows that this signal is necessary for this alteration because inactivation of the corollary reduces the compensation by frontal-cortex neurons. The identification of this relatively simple circuit specifies the organization of a corollary discharge in the primate brain for the first time and provides a specific example upon which consideration of the roles of corollary activity in other systems and for other functions can be evaluated.     

Visual working memory contaminates perception

Indirect evidence suggests that the contents of visual working memory may be maintained within sensory areas early in the visual hierarchy. We tested this possibility using a well-studied motion repulsion phenomenon in which perception of one direction of motion is distorted when another direction of motion is viewed simultaneously. We found that observers misperceived the actual direction of motion of a single motion stimulus if, while viewing that stimulus, they were holding a different motion direction in visual working memory. Control experiments showed that none of a variety of alternative explanations could account for this repulsion effect induced by working memory. Our findings provide compelling evidence that visual working memory representations directly interact with the same neural mechanisms as those involved in processing basic sensory events.     

Visual perception of complex shape-transforming processes

Morphogenesis—or the origin of complex natural form—has long fascinated researchers from practically every branch of science. However, we know practically nothing about how we perceive and understand such processes. Here, we measured how observers visually infer shape-transforming processes. Participants viewed pairs of objects (‘before’ and ‘after’ a transformation) and identified points that corresponded across the transformation. This allowed us to map out in spatial detail how perceived shape and space were affected by the transformations. Participants’ responses were strikingly accurate and mutually consistent for a wide range of non-rigid transformations including complex growth-like processes. A zero-free-parameter model based on matching and interpolating/extrapolating the positions of high-salience contour features predicts the data surprisingly well, suggesting observers infer spatial correspondences relative to key landmarks. Together, our findings reveal the operation of specific perceptual organization processes that make us remarkably adept at identifying correspondences across complex shape-transforming processes by using salient object features. We suggest that these abilities, which allow us to parse and interpret the causally significant features of shapes, are invaluable for many tasks that involve ‘making sense’ of shape.     

Visual perception of thick transparent materials

Under typical viewing conditions, human observers readily distinguish between materials such as silk, marmalade, or granite, an achievement of the visual system that is poorly understood. Recognizing transparent materials is especially challenging. Previous work on the perception of transparency has focused on objects composed of flat, infinitely thin filters. In the experiments reported here, we considered thick transparent objects, such as ice cubes, which are irregular in shape and can vary in refractive index. An important part of the visual evidence signaling the presence of such objects is distortions in the perceived shape of other objects in the scene. We propose a new class of visual cues derived from the distortion field induced by thick transparent objects, and we provide experimental evidence that cues arising from the distortion field predict both the successes and the failures of human perception in judging refractive indices.     

Visual texture perception and Fourier analysis

The relationship between the Fourier spectra of visual textures (represented by four hypothetical visual channels sensitive to spatial frequencies) and the perceptual appearance of the textures was investigated. Thirty textures were synthesized by combining various spatial frequencies of different amplitudes. Twenty subjects grouped the textures into 2, 3, 4, and 5 groups based on the similarity of their appearance. The groupings were analyzed by means of linear discriminant analysis using the activity of the four channels as predictor variables. The groupings were also examined by multidimensional scaling, and the resulting stimulus configuration was canonically correlated with the channel activity. The results of both analyses indicate a strong relationship between the perceptual appearance of the textures and their Fourier spectra. These findings suport a multiple-channel spatial-frequency model of perception.     

Visual half-field symmetry in orientation perception

The perception of orientation in the left and right visual half-fields has been investigated. No evidence for interfield differences was obtained for the discrimination of single lines by line matching or in magnitude of the systematic orientation distortion in orientation contrast and rod-and-frame experiments. Furthermore, increasing the time interval between test and comparison lines in successive matching provides no evidence for a differential operation of short-term spatial memory in the two hemispheres. It is concluded that hemispheric asymmetries do not arise at the level of sensory processing of spatial signals.     

Visual spatial perception and paternal deprivation

College men and women who were father deprived for at least 1 year from birth to 18 years of age or non-deprived were compared on the Spatial Relations Test of the Differential Aptitude Tests (DAT), the Identical Blocks Test (IBT) and the Water Level Test (WLT). There was a significant sex difference favoring men—as expected—on the IBT and WLT but not on the DAT. There was no significant effect of father deprivation on the mean performance on any test but there was a correlation between years of deprivation and WLT performance for men (r = 0.48,P < 0.001). No other correlation between deprivation and test performance was significant.     

Visual attention modulates audiovisual speech perception

Speech perception is audiovisual, as demonstrated by the McGurk effect in which discrepant visual speech alters the auditory speech percept. We studied the role of visual attention in audiovisual speech perception by measuring the McGurk effect in two conditions. In the baseline condition, attention was focused on the talking face. In the distracted attention condition, subjects ignored the face and attended to a visual distractor, which was a leaf moving across the face. The McGurk effect was weaker in the latter condition, indicating that visual attention modulated audiovisual speech perception. This modulation may occur at an early, unisensory processing stage, or it may be due to changes at the stage where auditory and visual information is integrated. We investigated this issue by conventional statistical testing, and by fitting the Fuzzy Logical Model of Perception (Massaro, 1998) to the results. The two methods suggested different interpretations, revealing a paradox in the current methods of analysis.