Role of convergence and binocular disparity in size constancy

Summary The effect of convergence on the perceived size of a light disk presented against a dark background was investigated by means of a projector stereoscope with polarizing filters. The results obtained with four subjects indicate that the logarithm of matched size decreases linearly as the convergence angle increases. The effect of binocular disparity was also examined by presenting a vertical bar beside the disk, but this did not add to the convergence effect. The results of a previous study on binocular disparity were reinterpreted as an effect of convergence difference between two objects. Implications of the present findings to the phenomenon of size constancy were discussed.

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Zusammenfassung Der Effekt der Konvergenz auf die wahrgenommene Größe einer gegen einen dunklen Hintergrund dargebotenen Lichtscheibe ist durch ein Projektorstereoskop anhand Polarisationsfiltern untersucht worden. Die Ergebnisse, die mit vier Versuchspersonen erworben wurden, zeigen, daß der Logarithmus der subjektiv gleichgestellten Größe sich linear mit zunehmendem Konvergenzwinkel verkleinert. Außerdem wurde der Effekt der Querdisparation durch das Darbieten eines vertikalen Lichtbalkens neben der Lichtscheibe untersucht; aber dieser war ohne Effekt. Die Ergebnisse einer vorhergehenden Untersuchung über die Querdisparation wurde neu interpretiert als ein Effekt der Konvergenzdifferenz zwischen zwei Objekten. Die Bedeutung des Versuches für das Phänomen der Größenkonstanz wurde erläutert.

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This study was performed at Chiba University in 1967 during the sabbatical year of the second author.     

Medication status of participants in psychopathology research: selective review of current reporting practices.

The majority of Ss included in studies of psychopathology are typically receiving psychoactive medication. In view of concerns regarding the confounding effects of psychoactive medication, it appears that researchers should provide information regarding at least the drug status of the Ss studied. A review of the articles on adult psychopathology that appeared in the Journal of Abnormal Psychology during a 5-year period, however, revealed that nearly 50% of reports on Ss presumably receiving psychoactive medications failed to specify the medication status of those Ss. Few studies (15%) provided adequate information regarding the types and dosages of psychoactive drugs received by the Ss. It is argued that researchers should provide a full report of the psychoactive drugs received by research participants and, when participants are unmedicated, to indicate the reasons for drug-free status.     

The locus of perceived equidistance in binocular vision

Empirical studies of the locus of perceived equidistance in binocular vision have revealed a characteristic change of its form, depending on absolute distance. This result is commonly taken to indicate influence of vergence-related binocular information, a conclusion that is by no means exclusively dictated by the data. Heller (1997) has suggested an alternative theoretical account that is based on the idea of independently combining the outcome of monocular input transformations without any form of binocular interaction. This article provides an experimental test of the structural assumption lying at the core of the axiomatic foundation of Heller's theory. I test the so-called Reidemeister condition under reduced cue conditions in two settings for each of 7 subjects. The results provide strong evidence for the validity of the Reidemeister condition and thus challenge the view that the locus of perceived equidistance depends on vergence-related binocular information. The discussion of the factors contributing to the monocular input transformations emphasizes the role of the optical properties of the eyes.     

Selective adaptation of monocular and binocular neurons in human vision

Psychophysical techniques were used to examine how subpopulations of visual neurons varying in their ocular dominance interacted in determining performance on a visual task. Using an asymmetric alternating adaptation of the left and right eyes, we manipulated the sensitivity of monocularly driven neurons while keeping the sensitivity of binocularly driven neurons constant. Relative threshold elevations were measured in the left eye, right eye, and both eyes of five observers following different ratios of alternating adaptation. It was found that whereas monocularly measured aftereffects varied monotonically as a function of the adaptation duration of the measured eye, the magnitude of the binocularly measured aftereffect remained constant regardless of how the adaptation was divided between the two eyes. This suggests that neurons differing in their ocular dominance pool their activity in determining sensitivity to a test target.     

Monocular and binocular vision in the control of goal-directed movement

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimensional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.     

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.     

Measurement of visual aftereffects and inferences about binocular mechanisms in human vision

There is conflicting evidence concerning the characteristics of binocular channels in the human visual system with respect to the existence of a 'pure' binocular channel that responds only to simultaneous stimulation of both eyes. Four experiments were conducted to resolve these discrepancies and to evaluate the evidence for the existence of such an exclusive binocular channel. In the first three studies, tilt aftereffects were measured after monocular adaptation. The relative sizes of the direct, interocularly transferred, and binocular aftereffects were not influenced by the configuration of the adapting pattern (experiment 1), or by the eye used for adaptation (experiment 2). There were also consistent interobserver differences in the relative sizes of the aftereffect seen after monocular adaptation (experiment 3). Taken together, these data raise questions about the appropriateness of a monocular adaptation paradigm for evaluating the presence of a pure binocular channel in observers with normal binocular vision. In experiment 4, in which the paradigm of alternating monocular adaptation was used, data were obtained that are consistent with the presence of a pure binocular channel.     

Voluntary attention in peripheral vision and its effects on acuity and differential thresholds

The three experiments described in this paper were intended to show whether voluntary attention to a particular part of the peripheral visual field had any effect on the accuracy of the subject's perception. Test objects near to threshold value (for acuity or for changes in luminance) were used. The experiments were also designed to study the possible distracting effect of other stimuli presented simultaneously in different parts of the field.

In Experiment 1 the subject could be given foreknowledge of the position in which an acuity test object would appear. In Experiment 2 the signal of where to attend was given simultaneously with the exposure of an acuity test object. In Experiment 3 differential thresholds for luminance were investigated by methods similar to those used in Experiment 2.

It was found in all these cases that the instructions to attend to a particular part of the peripheral field had no significant effect on perception unless there were simultaneously exposed “competing” stimuli in other parts of the field. The results support the view that, in peripheral vision, attention acts selectively on the immediate memory trace only when there is a complex pattern of stimulation.     

Effects of voluntary eye movement and convergence on the binocular appreciation of depth

Scaling techniques were employed to establish the relation between perceived distance ratio and physical distance ratio. Measurements were made both with and without free eye movement and under two states of convergence. The results were confirmed using a matching technique. With free eye movement, the perceived ratio is a monotonic increasing function of the physical ratio. Without eye movement, the perceived ratio generally increases, then decreases, as the physical ratio increases. For a given physical ratio, perceived distance ratio is less in the absence of voluntary eye movements. Convergence produces depth micropsia when eye movements are permitted, but not in their absence.     

Alexithymia as a potential source of symptom over‐reporting: An exploratory study in forensic patients and non‐forensic participants

The traditional interpretation of symptom over‐reporting is that it indicates malingering. We explored a different perspective, namely that over‐reporting of eccentric symptoms is related to deficits in articulating internal experiences (i.e., alexithymia). Given that alexithymia has been linked to sleep problems and that fatigue may fuel inattentive responding to symptom lists, we administered measures of alexithymia (TAS ‐20) and symptom over‐reporting (SIMS ), but also sleep quality (SLEEP ‐50) to forensic psychiatric outpatients (n = 40) and non‐forensic participants (n = 40). Forensic patients scored significantly higher on all three indices than non‐forensic participants. In the total sample as well as in subsamples, over‐reporting correlated positively and significantly with alexithymia, with r s being in the 0.50–0.65 range. Sleep problems were also related to over‐reporting, but in the full sample and in the forensic subsample, alexithymia predicted variance in over‐reporting over and above sleep problems. Although our study is cross‐sectional in nature, its results indicate that alexithymia as a potential source of over‐reporting merits systematic research.     

视觉正常的自闭症儿童双眼注视点间距的特点及其意义

视网膜上物象对应的外在注视点之间的距离, 即双眼注视点间距(distance of binoculars point of regard, DBPR)在自闭症谱系障碍(autism spectrum disorders, ASD)个体上存在异常的表现, 而ASD个体伴随较高的斜视发病率, 可能会对其双眼注视点间距产生影响。研究采用正弦曲线平滑追踪任务范式, 探索视觉正常的ASD儿童在动态刺激加工过程中DBPR的鉴别意义。结果发现, ASD儿童DBPR过大且具有跨任务类型的稳定性, 且与斜视无关。DBPR在大振幅、快速度的条件下具有优良的鉴别力, 并与自闭症行为量表总分以及感知觉维度显著正相关。结果表明, 双眼注视点间距具有良好的鉴别价值。     

Dark vergence in human infants: implications for the development of binocular vision

The resting position of binocular alignment in 1- to 4-month-olds, 6- to 18-month-olds, and adults was estimated by obtaining photographic measures of interpupillary distance in total darkness. The mean dark vergence position in the adult group corresponded to a distance of approximately 100 cm, similar to a previous estimate of 120 cm (Owens and Leibowitz 1976). The mean dark vergence position in the group of 1- to 4-month-olds was approximately 25 cm and in the group of 6- to 18-month-olds was approximately 50 cm. These near dark vergence positions in infants provide strong evidence that inaccuracies in binocular fixation during early infancy are not the result of a divergence bias. The developmental implications of dark vergence, accommodative vergence, and fusional vergence for the control of binocular alignment and distance perception during infancy are discussed.     

Haploscopic colour mixtures with and without contours in subjects with normal and disturbed binocular vision

Binocular mixtures of equiluminous components of different wavelengths were matched with additive monoptic mixtures of the same components. After a satisfactory match had been achieved, the luminance of each colour in the monoptic mixture was measured photometrically. After presentation of an orthogonal grating superimposed on the colour shown to one eye, the colour matching was repeated. The grating induced a strong dominance of the colour with which it was combined. Yet the uncontoured colour was not entirely suppressed, but contributed to the binocular colour to various degrees. In three subjects with anisometropic amblyopia in one eye the colour presented to the amblyopic eye contributed little or nothing to the haploscopic colour mixture, depending on the degree of amblyopia. This diminished contribution could not be enhanced by a grid. In three cases with strabismic amblyopia and in one case with strabismus alternans no haploscopic colour mixture effects could be demonstrated. The observations are discussed in the context of neurophysiological findings in the visual system of primates, and it is suggested that colour and contour are not transmitted through independent channels from the retina to the cortex.     

Evaluating and reporting data quality in eye movement research

In order to judge the degree of confidence one should have in the results of an experiment using eye movement records as data, it is necessary to have information about the quality of the eye movement data themselves. Suggestions are made for ways of assessing and reporting this information. The paper deals with three areas: characteristics of the eye movement signal, algorithms used in reducing the data, and accuracy of the eye position data. It is suggested that all studies involving eye movement data should report such information. Appendices include linear interpolation algorithms for mapping from the eye movement signal to stimulus space and a way of obtaining an index of accuracy for each data point.