Grasping tau.

In the present study a direct manipulation of the optical expansion pattern was carried out. What happens to the timing of the grasp movements involved in catching a ball when optical expansion information is not veridically provided? By using 2 luminescent balls of constant size and a luminescent ball that could change its diameter during flight, it was possible to manipulate the rate of optical expansion directly. The results of 2 experiments (binocular vision in Experiment 1 and monocular vision in Experiment 2) showed that the time of the maximal closing velocity of the hand--which conforms to the prediction if Ss use retinal expansion information--was later for the deflating ball than for the balls of constant size. Adjustments to the aperture of the hand in response to the different ball sizes, especially the adjustment of the hand to the deflating ball (even though Ss were not aware that the ball was deflating during its approach), point to a finely attuned perception-action coupling.     

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.     

Three- to eight-month-old infants' catching under monocular and binocular vision

We report a cross-sectional and a longitudinal experiment that examined developmental changes in the relative contribution of monocular and binocular variables in the guidance of interceptive arm movements. Three- to eight-month-old infants were observed while presented with differently sized balls that approached frontally with a constant velocity under both monocular and binocular viewing conditions. Movement onset indicated that with age infants increasingly came to rely on binocular variables in controlling the timing of the interceptive arm movements. That is, from 7 to 8 months of age movement onset was independent from object size under binocular but not under monocular viewing. In contrast, binocular viewing enhanced the spatial accuracy of the interceptive arm movements at all ages. We concluded that attunement to binocular information is a key process in infants' gaining adaptive control of goal-directed arm movements. However, interceptive arm movements entail the formation of multiple on-line couplings between optic and movement variables, each of which appears to develop at its own pace.     

The role of binocular information in ball catching

The role of binocular vision in a ball-catching task involving spatial uncertainty was examined in three experiments. In all three experiments, subjects' catching performance was evaluated during monocular and binocular viewing, in normal room lighting and in complete darkness with a luminescent ball. Subjects' performance was found to be significantly better with binocular than with monocular vision, especially under normal lighting conditions. In the second and third experiments, catching performance was evaluated in the presence of minimal visual frames, consisting of a series of light-emitting diodes (LEDs). In Experiment 2, the visual frame consisted of a single plane of LEDs, whereas in Experiment 3, the visual frame consisted of two planes of LEDs. Catching performance was found to be significantly better with the visual frame than in complete darkness, but this was true only for binocular viewing. This result supports the hypothesis that binocular convergence is used to scale perceived space and that this information enables subjects to contact the ball successfully. It was further found that postural sway varied between lighting conditions and that less sway was accompanied by higher performance. There was no effect of binocular viewing in this respect. In general, the results suggest two additive effects of viewing conditions: a direct effect of binocular vision on ball catching and an indirect effect of lighting on postural stability, which, in turn, affects catching performance.     

Has apparent size been tested as a factor in figural after-effects?

This experiment was designed to demonstrate that the effect of apparent size on the FAE has not been adequately tested. The subjects were run under binocular and under monocular viewing conditions. Binocular vision gave essentially the same results that had been obtained in previous binocular investigations. Monocular vision gave different results. It was concluded that the effect of apparent size on the FAE has not been demonstrated.     

Shedding some light on catching in the dark: perceptual mechanisms for catching fly balls

To catch a lofted ball, a catcher must pick up information that guides locomotion to where the ball will land. The acceleration of tangent of the elevation angle of the ball (AT) has received empirical support as a possible source of this information. Little, however, has been said about how the information is detected. Do catchers fixate on a stationary point, or do they track the ball with their gaze? Experiment 1 revealed that catchers use eye and head movements to track the ball. This means that if AT is picked up retinally, it must be done by means of background motion. Alternatively, AT could be picked up by extraretinal mechanisms, such as the vestibular and proprioceptive systems. In Experiment 2, catchers reliably ran to intercept luminous fly balls in the dark, that is, in absence of a visual background, under both binocular and monocular viewing conditions. This indicates that the optical information is not detected by a retinal mechanism alone.     

Adaptation to telestereoscopic viewing measured by one-handed ball-catching performance

A one-handed ball-catching task was used to study the disturbance of depth judgement induced by telestereoscopic viewing (ie viewing with increased effective interocular separation), the recovery of performance with experience in the telestereoscope, and the errors that subsequently arose when the telestereoscope was removed. The ball's trajectory was variable so that subjects had to control both the position and the timing of the grasp in order to catch the ball. On first wearing the telestereoscope, subjects closed the hand when the ball was approximately twice as far away from the eyes as the hand was. After fewer than twenty trials in the telestereoscope subjects were closing the hand at approximately the correct time and place, although rather more trials were needed for ball-catching performance to recover to normal. When the telestereoscope was removed there was an aftereffect, with subjects making the opposite errors to when they began the task. The existence of an aftereffect shows that the process of adaptation involves reevaluation rather than neglect of the misleading binocular information. Helmholtz's theory that telestereoscopes cause the world to be perceived as a scale model is considered. Initial misreaching is roughly consistent with this theory, but there are insufficient data to test it rigorously. Data from the aftereffect phase are clearly inconsistent with the theory. The results confirm the importance of binocular information in dynamic motor tasks, such as ball catching.     

Ecological relevance of stereopsis in one-handed ball-catching

The aim of this study was to compare one-handed catching performance between catchers with high (n = 10) and low (n = 10) binocular depth vision or stereopsis. In two sessions of 90 trials, tennis balls were projected at three different velocities towards the subject's shoulder region. Participants with good stereopsis were more successful, although the difference in number of correct catches fell short of significance. More specifically, catchers with low stereopsis made more temporal errors, but no differences in spatial errors. As the velocity of the ball increased, the initiation of the catch was delayed and catching performance decreased. The finding that stereopsis affected timing of the catch challenges the 'monocular tau hypothesis' in the control of interceptive timing, while the velocity effect shows that the act of catching a ball is not initiated at a constant time-to-contact.     

A Kinematic Analysis of Goal-directed Prehension Movements Executed under Binocular,Monocular, and Memory-guided Viewing Conditions

Vision is critical for the efficient execution of prehension movements, providing information about: The location of a target object with respect to the viewer; its spatial relationship to other objects; as well as intrinsic properties of the object such as its size and orientation. This paper reports three experiments which examined the role played by binocular vision in the execution of prehension movements. Specifically, transport and grasp kinematics were examined for prehension movements executed under binocular, monocular, and no vision (memory-guided and open-loop) viewing conditions. The results demonstrated an overall advantage for reaches executed under binocular vision; movement duration and the length of the deceleration phase were longer, and movement velocity reduced, when movements were executed with monocular vision. Furthermore, the results indicated that binocular vision is particularly important during “selective” reaching, that is reaching for target objects which are accompanied by flanker objects. These results are related to recent neuro psychological investigations suggesting that stereopsis may be critical for the visual control of prehension.     

The Optics and Actions of Catching Fly Balls: Zeroing Out Optical Acceleration

Advancing or retreating so as to maintain a projectile's constant vertical optical velocity was suggested by Chapman (1968) as a possible basis for locomotion in ball catching. Three experiments examined this thesis. In Experiments I and 2, the positions of balls and catchers were videotaped to see if the movements of the catchers canceled optical acceleration. Such canceling was indeed observed until just prior to the catch for hand-thrown balls (Experiment 1). The monocular availability of the information predicts success with monocular viewing, confirmed in Experiment 2 with machine-thrown balls. In Experiment 3, observers judged whether a ball (represented as a moving dot on a computer screen) would land at, in front of, or behind them. Performance was above chance, but only some observers used acceleration. Together, the experiments provide broad, though not unequivocal, support for the utilization of optical acceleration to guide locomotion in catching.     

Contribution of binocular vision to the performance of complex manipulation tasks in 5–13 years old visually-normal children

Individual studies have shown that visuomotor coordination and aspects of binocular vision, such as stereoacuity and dynamic vergence control, continue to improve in normally developing children between birth and early teenage years. However, no study has systematically addressed the relationship between the development of binocular vision and fine manipulation skills. Thus, the aim of this cross-sectional study was to characterize performance of complex manipulation tasks during binocular and monocular viewing. Fifty-two children, between 5 and 13 years old, performed 2 manipulation tasks: peg-board and bead-threading under randomized viewing conditions. Results showed that binocular viewing was associated with a significantly greater improvement in performance on the bead-threading task in comparison to the peg-board task and the youngest children showed the greatest decrement in task performance under the monocular viewing condition when performing the bead-threading task. Thus, the role of binocular vision in performance of fine manipulation skills is both task- and age-dependent. These findings have implications for assessment of visuomotor skills in children with abnormal binocular vision, which occurs in 2–3% of otherwise typically developing children.     

Critical flicker frequency under monocular and binocular conditions.

Critical flicker frequency of 40 undergraduate students, 20 men and 20 women whose mean age was 19.3 yr., was measured under monocular and binocular viewing conditions, using the Lafayette Visual Perception Control with Display Unit. Half of the subjects received monocular treatment first and binocular treatment second, and the other half received the treatments in the reversed order. A 2-min. rest was allowed between these treatments. Analysis shows that mean CFF under the monocular condition was significantly lower than that under binocular conditions. The findings were discussed in terms of visual constraint and eye strain and fatigue under the monocular viewing condition.     

Binocular vision and spatial perception in 4- and 5-month-old infants

Four experiments investigated the relation between the development of binocular vision and infant spatial perception. Experiments 1 and 2 compared monocular and binocular depth perception in 4- and 5-month-old infants. Infants in both age groups reached more consistently for the nearer of two objects under binocular viewing conditions than under monocular viewing conditions. Experiments 3 and 4 investigated whether the superiority of binocular depth perception in 4-month-olds is related to the development of sensitivity to binocular disparity. Under binocular viewing conditions in Experiment 3, infants identified as disparity-sensitive reached more consistently for the nearer object than did infants identified as disparity-insensitive. The two groups' performances did not differ under monocular viewing conditions. These results suggest that, binocularly, the disparity-sensitive infants perceived the objects' distances more accurately than did the disparity-insensitive infants. In Experiment 4, infants were habituated to an object, then presented with the same object and a novel object that differed only in size. Disparity-sensitive infants showed size constancy by recovering from habituation when viewing the novel object. Disparity-insensitive infants did not show clear evidence of size constancy. These findings suggest that the development of sensitivity to binocular disparity is accompanied by a substantial increase in the accuracy of infant spatial perception.     

Infants’ ability to respond to depth from the retinal size of human faces: Comparing monocular and binocular preferential-looking

To examine sensitivity to pictorial depth cues in young infants (4 and 5 months-of-age), we compared monocular and binocular preferential looking to a display on which two faces were equidistantly presented and one was larger than the other, depicting depth from the size of human faces. Because human faces vary little in size, the correlation between retinal size and distance can provide depth information. As a result, adults perceive a larger face as closer than a smaller one. Although binocular information for depth provided information that the faces in our display were equidistant, under monocular viewing, no such information was provided. Rather, the size of the faces indicated that one was closer than the other. Infants are known to look longer at apparently closer objects. Therefore, we hypothesized that infants would look longer at a larger face in the monocular than in the binocular condition if they perceived depth from the size of human faces. Because the displays were identical in the two conditions, any difference in looking-behavior between monocular and binocular viewing indicated sensitivity to depth information. Results showed that 5-month-old infants preferred the larger, apparently closer, face in the monocular condition compared to the binocular condition when static displays were presented. In addition, when presented with a dynamic display, 4-month-old infants showed a stronger ‘closer’ preference in the monocular condition compared to the binocular condition. This was not the case when the faces were inverted. These results suggest that even 4-month-old infants respond to depth information from a depth cue that may require learning, the size of faces.     

Introduction: A Cognitive Science Slam in Honor of Guy Van Orden

Illusory depth perception experienced in driving simulators is afforded by monocular depth information contained in visual displays. Presumably binocular convergence and binocular disparity, though useful for depth perception in real environments, may poorly contribute to illusory depth in a driving simulator. Instead, they may generate conflicting information by revealing the distance of the display screen and its flatness. Nevertheless, illusory depth induced by monocular information contained in visual displays usually produces enough immersion and realism to create the illusion of driving in a real environment.

Many authors have noted improved depth perception in paintings, photographs, and even in drawings when viewed monocularly. However, this effect, known as monocular advantage, has never been explored in driving simulation. The purpose of this experiment was to assess whether the effect might exist in driving simulation. It was expected that drivers would perceive distances in depth better and more accurately with a monocular than with a binocular viewing of the display. Distance estimates were evaluated for two types of driving maneuvers referred to as alignment and bisection. Results showed that when significant performance differences between monocular and binocular viewing conditions occurred, target cars were perceived farther in depth and more accurately using monocular vision.

Alternative viewing conditions using both eyes are discussed at the end of the article.     

Effect of ecological viewing conditions on the Ames' distorted room illusion

Ecological theory asserts that the Ames' distorted room illusion (DRI) occurs as a result of the artificial restriction of information pickup. According to Gibson (1966, 1979), the illusion is eliminated when binocular vision and/or head movement are allowed. In Experiment 1, to measure the DRI, we used a size-matching technique employing discs placed within an Ames' distorted room. One hundred forty-four subjects viewed the distorted room or a control apparatus under four different viewing conditions (i.e., restricted or unrestricted head movement), using monocular and binocular vision. In Experiment 2, subjects viewed binocularly and were instructed to move freely while making judgments. Overall, the main findings of this study were that the DRI decreased with increases in viewing access and that the DRI persisted under all viewing conditions. The persistence of the illusion was felt to contradict Gibson's position.     

Binocular fixation in the newborn baby.

Three experiments are reported in which the newborn baby's ability to fixate binocularly was investigated, using the corneal reflection technique for measuring eye fixation position. Two criteria for consistent binocular fixation were assessed. These are (1) the two eyes will be optically more divergent when fixating more distant targets, and (2) each eye will be scored as being on-target when corrections for the expected deviations of the pupil center from the fixated stimulus are introduced.In the first experiment vertical arrays of lights were separately shown at distances of 10 and 20 in. from the subjects' eyes (with the retinal image size and luminance of the stimuli held constant). The 12 newborns who gave results at both viewing distances reliably converged to both stimuli, the optical divergence of the pupil centers of the eyes increasing with presentation of the more distant stimulus. In Expt 2 similar stimuli at 5 and 10 in. from the eyes were shown. It was again the case that the subjects reliably converged to the stimulus at 10 in. This was no so for the stimulus at 5 in., and many subjects fixated this stimulus with monocular vision. The failure to converge is probably due to an inability to accommodate to this near distance. In Expt 3 different stimuli (a vertical strip of light, an outline triangle and square, and an array of squares) were presented a constant distance (10 ± 1 in.) from the eyes. The majority of the 15 subjects binocularly fixated all three stimuli: for those subjects who failed to converge consistently to these stimuli the observed alternatives to binocular fixation were monocular fixation, divergent strabismus, and a third category of response that is most probably an indication of inattention to the stimulus. It can be concluded that the newborn baby possesses the ability to fixate binocularly an appropriately presented stimulus, and has the basic requirements for binocular vision.     

Recognizing novel views of three-dimensional objects.

The purpose of the experiments reported was to examine how novel, three-dimensional shapes are represented in long-term memory and how this might be differentially affected by monocular and binocular viewing. Three experiments were conducted. The first experiment established that slide projections of the novel objects could be recognized readily if seen in the same orientation as seen during learning. The second and third experiments examined generalization to novel depth rotations of the objects. The second experiment used slide projections of the objects. The results indicated that the representation of the objects seen during training was quite viewpoint-specific as recognition of objects in novel orientations was relatively poor. In the third experiment subjects were shown the real objects under monocular or binocular viewing. Overall, the results are consistent with a growing body of recent research showing that, at least under certain conditions, the visual system stores viewpoint-specific representations of objects.     

Information and action in punching a falling ball

Lee, Young, Reddish, Lough, and Clayton (1983) reported that the timing control of jumping and vertically punching a dropping ball exploits the inverse of the rate of change of optical expansion, τ(r). We raise a number of methodological and logical criticisms against their experiment and conclusions and attempt to rectify them by examining elbow joint angles only,in seated punchers, under both monocular and binocular conditions, with two ball sizes, dropped from two heights. Differences between the binocular and monocular cases suggest the exploitation of different information. We present several techniques to help determine the operative variable(s) controlling the action. The optical variable used to initiate and guide flexion appeared to be expansion velocity (looming), rather than τ(r); extension appeared to be under the control of different variables in the monocular and binocular cases. Simulations using single variables and single perceptuo-motor intervals were of mixed success.     

Three-dimensional interpretation of quadrilaterals.

The three-dimensional interpretation of two-dimensional images was studied by using quadrilateral patterns, and some relationships between their structure, depth, and shape interpretations were analyzed under various viewing conditions. We defined rectangular and nonrectangular viewing conditions as follows: the viewing condition in which the quadrilateral, including parallel sides, could be a projection from a rectangle and the viewing condition in which it could not be so. For 9 subjects, 10 measurements were made in each experiment. Analysis showed that a pair of parallel sides of a quadrilateral were viewed as parallel to the viewer's forehead when the sides were horizontal in the image plane and were seen as slanting in depth if they were slanted in the image plane. The quadrilateral composed of parallel and nonparallel sides was perceived as rectangular when viewed with foveal vision even though under the nonrectangular viewing condition, if that viewing condition was not so different from the rectangular viewing condition. The quadrilateral did not appear to be rectangular when viewed in peripheral vision even though the rectangular viewing condition was used.