Differential resistance to distortion as a functional property of two structural parameters of two dimensional line drawings

Two structural parameters of two dimensional drawings, sidedness and regularity, are systematically varied and their relationship to the breakdown of binocular fusion (doubling of image) as a function of increasing lateral separation of dichoptically presented images is explored. Sidedness is not found to be systematically significant parameter, while regularity is seen to operate across figures (independently of sidedness). A predictive analysis, in terms of the Gestalt variables of “good form” is examined, and the results discussed in terms of these variables, a personality dimension and uncertainty.     

Visual stimuli for strabismic suppression

The effects of orientation and spatial frequency of grating stimuli upon suppression were examined with a binocular rivalry paradigm in a group of ten strabismic patients and in a control normal group. Duration, frequency, and period of rivalry were examined as functions of differences in orientation and spatial frequency of dichoptic achromatic sinusoidal gratings. Records were made of responses by the sighting and by the nonsighting eye as well as responses during periods of combined binocular vision. Strabismic subjects reported normal binocular rivalry when presented with gratings of dissimilar orientation. Suppression of the deviating eye in strabismic subjects occurred with stimuli of similar orientation and was unaffected by spatial-frequency differences between dichoptic stimuli. Suppression was most intense under conditions that normally stimulate stereopsis and sensory fusion.     

Inability to wink an eye and eye dominance.

Data from 56 subjects in Grades 4 to 12 only able to wink one eye indicated that the non-winking eye was used as the dominant one in tests on monocular and binocular sighting.     

The relationship between sighting dominance and the fading of a stabilized retinal image

The fading of a stabilized retinal image in the sighting and the nonsighting dominant eye was studied using the Haidinger’s brush target. Reaction time to the complete disappearance of the stabilized image was significantly longer when the target was input to the sighting eye. The greater persistence of stabilized targets in the sighting eye suggests possible differences in the neural channels from the two eyes or processing differences in the two monocular channels that are related behaviorally to eye dominance.     

The assessment of motor control in sighting dominance using an illusion decrement procedure

Walls (1951) proposed that perceptual asymmetries between the sighting dominant and the nonsighting dominant eyes were based upon differences in the monitoring of eye movements. The present research explored this hypothesis in the context of an illusion decrement paradigm. Since illusion decrement seems to occur only under conditions of free eye-movement inspection, it was reasoned that any motoric asymmetries would manifest themselves through differences in the rate and extent of decrement. These predictions were partially confirmed. The sighting eye manifested greater illusion decrement, but the effect remained specific to conditions where both eyes were stimulated. In addition, asymmetries in the interocular transfer of illusion decrement were found to favor the sighting dominant eye.     

Hemiretinal differences in face recognition: accuracy versus reaction time

A face-recognition task involving monocular presentation of laterally displaced stimuli yielded a nasal hemiretinal advantage for reaction time for correct identifications, but a temporal hemiretinal advantage for accuracy (d'). These hemiretinal effects, in conjunction with eye dominance, could in principle distort or obscure interpretations of hemispheric processing differences obtained with binocular stimulation.     

Intersubject variability in perceived oscillation as a function of threshold for binocular disparity.

Four groups of 15 female subjects each were classified along a quantitative dimension for proportion of perceived oscillation and threshold for binocular disparity. Analyses of variance showed that significant differences in proportion of perceived oscillation were accompanied by significant differences in threshold for binocular disparity for perceivers of "high" and "low" oscillation (p less than .05). For perceivers of "intermediate" oscillation significant differences in proportion of perceived oscillation but not threshold for binocular disparity were found. It was suggested that: (1) intersubject variability in perceived oscillation may be governed by the threshold for binocular disparity, (2) "low" perceivers may be especially sensitive to the magnitude of the cue, (3) "intermediate" perceivers' subjective reports may be primarily dependent on response criteria and the multiplicity of subjective factors which constitute it, (4) "high" perceivers apparently have least response sensitivity and they cannot maintain a consistent response criterion.     

The Localization of Pitch Perception on the Basilar Membrane

Durations of four categories of perceptions in the binocular rivalry of 3.9° bright contours were considered. Distributions of durations of perceptions of each of the rivalry categories and of all rivalry reports together were tested against five standard distributions. The empirical distributions showed no tendency to fit any of the standard theoretical distributions well. The results suggest that speculations concerning the underlying mechanisms of binocular rivalry based on observations of the durations of rivalry reports may not be useful until the distributions of durations are satisfactorily described.     

The acquisition of catching under monocular and binocular conditions

The effects of binocular and monocular viewing on spatial and temporal errors in one-handed catching were investigated in two experiments. The first experiment-using expert catchers-recorded more spatial errors under the monocular than under the binocular condition. No significant differences in the number of temporal errors were apparent. In a second experiment, which paradigm, relatively poor catchers were trained under both vision conditions. Its objective was to investigate whether the superior results obtained under the binocular condition in the first experiment, for the number of catches and number of spatial errors, could be attributed simply to the fact that subjects had more experience with binocular than monocular viewing. The following results occurred after a period of training (a) a significant reduction in the number of spatial errors under the monocular condition, reaching a level similar to that under the binocular condition; (b) no significant reduction in the number of spatial errors when subjects transferred from monocular to binocular viewing, and significantly more spatial errors when subjects transferred from binocular to monocular viewing; and (c) a training-sequence effect. The latter effect indicates that subjects had more benefit from training in the sequence monocular-binocular than vice versa. These findings are discussed in the context of the strategies of specificity of learning and use of multisources.     

Stereo-motion cooperation and the use ofmotion disparity in the visual perception of 3-D structure

When an observer views a moving scene binocularly, both motion parallax and binocular disparity provide depth information. In Experiments lA-1C, we measured sensitivity to surface curvature when these depth cues were available either individually or simultaneously. When the depth cues yielded comparable sensitivity to surface curvature, we found that curvature detection was easier with the cues present simultaneously, rather than individually. For 2 of the 6 subjects, this effect was stronger when the component of frontal translation of the surface was vertical, rather than horizontal. No such anisotropy was found for the 4 other subjects. If a moving object is observed binocularly, the patterns of optic flow are different on the left and right retinae. We have suggested elsewhere (Cornilleau-Pérès & Droulez, in press) that this motion disparity might be used as avisual cue for the perception of a 3-D structure. Our model consisted in deriving binocular disparity from the left and right distributions of vertical velocities, rather than from luminous intensities, as has been done in classical studies on stereoscopic vision. The model led to some predictions concerning the detection of surface curvature from motion disparity in the presence or absence of intensity-based disparity (classically termedbinocular disparity). In a second set of experiments, we attempted to test these predictions, and we failed to validate our theoretical scheme from a physiological point of view.     

Fragmentation of monocular afterimages in individuals with and without normal binocular vision

Monocular afterimages of a vertical line were generated in each eye of binocularly normal individuals and of those lacking binocular single vision or stereopsis as a consequence of childhood strabismus. Fragmentations and disappearances of the afterimages occurred less frequently in the strabismic than in the normal subjects; they were also less frequent in the dominant (nonamblyopic) eyes of the strabismics than in their amblyopic eyes. The afterimages remained visible for longer when presented to the dominant eyes of the strabismic subjects, and a similar effect was found between the sighting dominant and nondominant eyes of normal subjects.     

Aging and the perception of 3-D shape from dynamic patterns of binocular disparity

In two experiments, we investigated the ability of younger and older observers to perceive and discriminate 3-D shape from static and dynamic patterns of binocular disparity. In both experiments, the younger observers' discrimination accuracies were 20% higher than those of the older observers. Despite this quantitative difference, in all other respects the older observers performed similarly to the younger observers. Both age groups were similarly affected by changes in the magnitude of binocular disparity, by reductions in binocular correspondence, and by increases in the speed of stereoscopic motion. In addition, observers in both age groups exhibited an advantage in performance for dynamic stereograms when the patterns of binocular disparity contained significant amounts of correspondence "noise." The process of aging does affect stereopsis, but the effects are quantitative rather than qualitative.     

Adaptation to uniocular image magnification: Is the underlying shift proprioceptive?

Ss wore a 4% overall size lens (OSL) before one eye while they engaged in 20 min of binocular exploration of a typical indoor environment. Tests before and after the exposure period were conducted to determine whether or not OSL exposure leads to shifts in depth judgments based on binocular disparity. No significant shifts were observed. These results were applied to an evaluation of two contrasting hypotheses that have been proposed to explain adaptation to meridional size lens (MSL).     

A statistical model of binocular disparity

Binocular disparity provides important information about the three-dimensional structure of the environment. The current study sought to complement our geometrical understanding of binocular vision by considering the distributions of horizontal and vertical disparities that might be expected in images of the natural environment, using a simple environmental model. It was observed that the distribution of disparities depends critically on fixation, and varies greatly from one image location to another. The results were considered in relation to computational models of binocular stereopsis, and compared to two known properties of the visual system—the small disparity preference in disparity matching, and the influence of eccentricity on Panum's fusional limit. Overall, the study characterizes the binocular disparities that are likely to be encountered in the real world scenes, and discusses the implications of these for our understanding of binocular visual systems.     

Latency differences in monoptic and dichoptic shape and color decision making

Past research based on the McCollough effect and efficacy of chromatic cues in stereopsis suggests that color information is difficult to process binocularly as compared to form information. This study evaluates this proposition using a reaction time paradigm. Subjects decided whether two simultaneous visual stimuli were the same in shape or color. With presentation to the same eye, color reaction times led shape latencies. Presenting one target to one eye and one to the other slowed color times. Delaying one target by 500 msec yielded dichoptic and monoptic color decisions faster than shape. The results are related to the relationships of color and contrast pathways and possible differences in binocular rivalry.     

Visual symmetry perception in early onset monocular blindness

Symmetry detection is impaired by abnormal binocular vision development such as in amblyopia. However, the detection of symmetry has never been investigated in cases where input from one eye is profoundly compromised. Testing monocularly blind (MB) individuals represents a unique opportunity to investigate whether symmetry salience relies on a normally developed binocular visual system. In a visual symmetry detection task using dot patterns, congenitally MB showed comparable accuracy to normally sighted individuals viewing monocularly. This included better detection of vertically than horizontally symmetric patterns. However, the MB were slower than controls in detecting a symmetrical pattern. In a control target-detection task, no significant differences in performance were observed between these groups. Overall, normal developing binocular vision does not appear necessary for the visual system to detect the presence of visual symmetry. However, optimal detection mechanisms may be dependent on binocular summation or other processes dependent on input from both eyes.     

Varieties of Binocular Interaction in Human Vision

Binocular processing was investigated using a quantitative, process-oriented metatheory of response times. The analyses are not confined to particular distributional assumptions or specific models. Upper and lower performance boundaries for probability summation in parallel processing are defined and compared with observed distributions of reaction times using a variety of dichoptic stimuli. Performance that exceeds the upper bound strongly suggests faciliatory convergence between the two eyes (binocular channel summation). Performance below the lower bound suggests that inputs to the two eyes are processed serially. The results indicate that binocular channel summation in subjects with normal stereo vision requires targets of the same luminance polarity (paired increments or decrements) in corresponding retinal locations. When corresponding retinal locations are stimulated with opposing luminance polarities (increment to one eye, decrement to the other), performance is consistent with probability summation, indicating that parallel ON and OFF pathways remain segregated at least to the level of binocular fusion. Further analyses of data from a stereo-blind observer suggests serial processing of binocular inputs.     

Delinquency, sidedness, and sex

One hundred and thirty male and 213 female college students responded to a self-report delinquency and crime measure and to a scale of sidedness preferences. Consistent with most of the literature on official delinquency and crime, left handedness was positively associated with involvement in several forms of delinquency (including some degree of criminality) among males. Other measures of sidedness among males largely failed to correlate with delinquency, however. Among females, sidedness was much less systematically related to delinquency than among males.     

The effects of fear arousal,fear position,fear exposure,and sidedness on compliance with dietary instructions

Investigated the effects of fear arousal and sidedness variables on compliance with a dietary regimen. Experiments involved 202 women volunteers who were 10 per cent or more overweight, and aged 20-60 years. Experiment 1 involved a 3 (low, medium, high fear) × 2 (single, multiple exposure to fear message) × 2 (one-, two-sided communication) design. The fear levels involved discussing the health hazards of obesity. Experiment 2 manipulated the fear-message position relative to the recommendations (fear-recommendations, recommendations-fear, fear-delay-recommendations). Persuasive impact was measured via follow-up weight checks at 2, 4, 8, and 16 weeks. Results indicate nonsignificant effects from sidedness and pre-standardised fear levels. Using subjects' fear arousal ratings medium fear is significantly better (p < .025), supporting Janis's curvilinear hypothesis. A single exposure to the fear message is superior (p < .025) to multiple exposures, the interaction with time being highly significant (p < .001). Experiment 2 results indicate the optimum position for the fear message as immediately prior to recommendations (p < .025). Results support both cognitive and fear-reduction hypotheses, but the latter is favoured.     

Binocular unmasking with unequal interocular contrast: the case for multiple Cyclopean eyes.

Under certain conditions, the detection threshold for a sinusoidal grating embedded in a noisy background may be an order of magnitude lower when binocular cues are available than when monocular cues only are present. Such binocular unmasking occurs only when the degree of interocular disparity for the target differs from that of the background. Two classes of models have been advanced to account for such unmasking. The first assumes that orientation-specific, spatial frequency channels in each eye encode the amplitude and phase of the spatial frequency component of the pattern the channel is tuned to detect. Thus, a difference in interocular disparity between target and background could result in interocular amplitude and/or phase differences in left- and right-eye spatial frequency channels. When, however, there are no disparity differences between target and background, there will be no interocular differences in amplitude and phase in the left- and right-eye channels. In this model, then, binocular unmasking reflects the binocular system's ability to respond to interocular amplitude and/or phase differences in the patterns presented to the two eyes. In the second class of models, it is assumed that the left- and right-eye patterns are first summed to form a "Cyclopean" eye. In these models, detection depends on the effect this summation process has on the power spectrum of the summated patterns. To decide between these two classes of models, we observed the occurrence of binocular unmasking when (1) the contrast of masker and signal was varied identically in both eyes and (2) the contrast of masker and signal was varied in one eye only. Consistent with our previous research, we found that the results can be accounted for in terms of a linear summation model of binocular unmasking; the alternative interocular phase detection model was disproved. The implications of these findings for binocular contrast summation in the absence of visual noise are discussed.