Visual movement perception: A comparison of absolute and relative movement discrimination

It is proposed that there are two types of visual movement perception, absolute and relative. The former occurs when an object is seen to move in an otherwise homogeneous (or at least locally homogeneous) visual field. Relative judgments occur when one object is seen to move with respect to another, i.e., the separation between them is seen to change. Quantitative models for both processes are developed, and an experiment reported for which the models seem appropriate. The results appear relevant to a theory of size of length perception as well as to the general perceptual issue of absolute and relative judgments.     

Visual movement perception in deaf and hearing individuals

A number of studies have investigated changes in the perception of visual motion as a result of altered sensory experiences. An animal study has shown that auditory-deprived cats exhibit enhanced performance in a visual movement detection task compared to hearing cats (Lomber, Meredith, & Kral, 2010). In humans, the behavioural evidence regarding the perception of motion is less clear. The present study investigated deaf and hearing adult participants using a movement localization task and a direction of motion task employing coherently-moving and static visual dot patterns. Overall, deaf and hearing participants did not differ in their movement localization performance, although within the deaf group, a left visual field advantage was found. When discriminating the direction of motion, however, deaf participants responded faster and tended to be more accurate when detecting small differences in direction compared with the hearing controls. These results conform to the view that visual abilities are enhanced after auditory deprivation and extend previous findings regarding visual motion processing in deaf individuals.     

Visual movement perception: A comparison of sensitivity to vertical and horizontal movement

A psychophysical model that provides separate measures of judgmental standards and sensitivity is utilized to compare an O’s visual sensitivity for vertical and horizontal movement. The analysis indicates no consistent difference in sensitivity; those asymmetries that do exist simply appear to be due to idiosyncratic judgmental standards.     

Visual prosody and speech intelligibility: head movement improves auditory speech perception

People naturally move their heads when they speak, and our study shows that this rhythmic head motion conveys linguistic information. Three-dimensional head and face motion and the acoustics of a talker producing Japanese sentences were recorded and analyzed. The head movement correlated strongly with the pitch (fundamental frequency) and amplitude of the talker's voice. In a perception study, Japanese subjects viewed realistic talking-head animations based on these movement recordings in a speech-in-noise task. The animations allowed the head motion to be manipulated without changing other characteristics of the visual or acoustic speech. Subjects correctly identified more syllables when natural head motion was present in the animation than when it was eliminated or distorted. These results suggest that nonverbal gestures such as head movements play a more direct role in the perception of speech than previously known.     

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 markings

Markings, such as designs, writings, diagrams, and depictions, are expressive and communicative human artifacts. The conventional assumption that findings from the study of the visual perception of markings—in particular, of pictures—can be generalized to real-world perception is examined and found to be false. The processes involved in the visual perception of the world and in the visual perception of markings differ in significant ways, and generalizations from one to the other must be undertaken with caution. The visual perception of markings is an identifiable and separate area of study. Implications for a general theory of the perception of markings are examined, and the perception of markings is contrasted with real-world perception.     

Visual movement discrimination

Data are presented which support a mathematical model for visual movement perception. An observer’s ability to judge the relative position of two successively presented points of light in an otherwise dark room is shown to diminish as the inter-stimulus interval is increased. However, a measure of visual position memory appears to remain invariant a5 this interval is varied. Neither the degree of head stabilization nor whether viewing is monocular or binocular appreciably alters this measure.     

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 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 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 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.