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.     

The role of attention in one-handed catching

The present study investigated the contribution of attention to one-handed catching success. A group of skilled (n = 8) and less skilled (n = 9) male subjects were compared in their ability to process secondary task information while executing a primary one-handed catching task. On 40% of the trials, a secondary visual stimulus (SVS) was presented in the peripheral visual field at predetermined times during the flight of the ball. On these trials, the subject was required to complete the one-handed catch and immediately throw the ball at a stationary target. Less skilled subjects made significantly more catching errors under both normal viewing and dual-task processing conditions. The differences were due to errors of positioning rather than grasping. Positioning of the hand appears to require visual attention regardless of skill level, as both skill groups experienced increased difficulty processing secondary task information as the ball approached the catching hand.     

Specificity of practice in a ball interception task.

Learning of an aiming task has been shown to be specific to the sources of afferent information available during practice. However, this has not been the case when a one-hand ball-catching task has been used. The goal of the present study was to determine the cause of these conflicting results. Participants practiced an interception task in either a normal vision condition or a ball-only condition. They were all then transferred to the ball-only condition, using either the same ball trajectories as in acquisition or different ones. Being transferred from a normal vision condition to a ball-only condition resulted in a significant increase in spatial interception errors, thus supporting the specificity of practice hypothesis. Using new ball trajectories in transfer caused a significant increase in error for all participants. The pattern of errors observed when new ball trajectories were used suggests that participants had difficulty correlating information about the location of their arm via proprioception and a combination of retinal and extra-retinal information about the ball trajectory.     

Texture size specificity in the slant aftereffect

Transfer of the median plane slant aftereffect was assessed across changes in stimulus texture size (sine-wave grating frequency). Under binocular viewing, reliable decrements in aftereffect magnitude were observed when texture size was changed, compared with no-change control conditions. Under monocular viewing conditions, no significant aftereffects were found. The results indicate a spatial-frequency-specific component of binocular slant aftereffects.     

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.     

Cues to viewing distance for stereoscopic depth constancy.

A veridical estimate of viewing distance is required in order to determine the metric structure of objects from binocular stereopsis. One example of a judgment of metric structure, which we used in our experiment, is the apparently circular cylinder task (E B Johnston, 1991 Vision Research 31 1351-1360). Most studies report underconstancy in this task when the stimulus is defined purely by binocular disparities. We examined the effect of two factors on performance: (i) the richness of the cues to viewing distance (using either a naturalistic setting with many cues to viewing distance or a condition in which the room and the monitors were obscured from view), and (ii) the range of stimulus disparities (cylinder depths) presented during an experimental run. We tested both experienced subjects (who had performed the task many times before under full-cue conditions) and na?ve subjects. Depth constancy was reduced for the na?ve subjects (from 62% to 46%) when the position of the monitors was obscured. Under similar conditions, the experienced subjects showed no reduction in constancy. In a second experiment, using a forced-choice method of constant stimuli, we found that depth constancy was reduced from 64% to 23% in na?ve subjects and from 77% to 55% in experienced subjects when the same set of images was presented at all viewing distances rather than using a set of stimulus disparities proportional to the correct setting. One possible explanation of these results is that, under reduced-cue conditions, the range of disparities presented is used by the visual system as a cue to viewing distance.     

Misinterpretation of instructions in an aftereffect task

Some subjects in studies of kinesthetic aftereffect erroneously believe the task is to show the width of the aftereffect inducing rather than the standard stimulus. Although such subjects may be encountered rarely, the errors they make are very large. Precautionary steps are indicated.     

Multiple information sources in interceptive timing

This study was designed to explore the limitations of tau (τ) as an explanatory construct for the timing of interceptive action. This was achieved by examining the effects of environmental structure and binocular vision on the timing of the grasp in a simple one-handed catch. In two experiments, subjects were required to catch luminous balls of different diameters (4, 6, 8 and 10 cm) in a completely darkened room. In the first experiment the influence of the presence vs. absence of an environmental background structure (both under monocular viewing) was tested, and in the second experiment the influence of monocular vs. binocular vision was examined. It was found that irrespective of the presence of environmental structure, an effect of ball size occurred in the monocular viewing conditions. That is, in monocular viewing conditions the grasp was initiated and completed earlier for the larger balls as compared to the smaller ones, while in the binocular viewing condition subjects behaved in accordance with a constant time to contact strategy: no effects of ball size were found. It is concluded that under binocular viewing a binocular information source is used, while in the monocular viewing condition a lower order information source like image size or image velocity is probably involved.     

Dynamic Visual Acuity and Performance in a Catching Task

Each of 30 Ss was given tests of dynamic and static visual acuity and then participated in a ball-catching task. Performance in the latter task was an inverted U-shaped function of duration of the occluded period, the time between the termination of the 80-msec. viewing period and the estimated onset of the “latency period” (the point in time at which the ball could no longer serve to cue Ss response). Dynamic and static visual acuity scores were not significantly correlated but, with static visual acuity partialled out, dynamic visual acuity and catching performance were significantly correlated.     

Checkerboard-specific color aftereffects: A failure to find effects of perceptual organization

Two experiments investigated the effects of differing perceptual organizations of reversible figures on McCollough aftereffects. Experiment 1 used colored checkerboard inducing stimuli and achromatic grating test stimuli. While some subjects tended to organize the checkerboards into rows and/or columns and others to organize them into obliques, these variations did not result in differences in aftereffect direction or magnitude. Experiment 2 induced an aftereffect with colored gratings and tested with checkerboards, gratings, and a reversible concentric octagon pattern. Perceptual organization had no effect on results for checkerboards, but was related to aftereffect strength for the octagon pattern. Indirect evidence suggests that, in the latter case, differences in aftereffect strength may have influenced the perceived organization, rather than vice versa. Finally, regardless of the specific organization perceived, spontaneous viewing of all test stimuli produced stronger aftereffects than were found when subjects reorganized the pattern. This may have resulted from a viewing strategy associated with reorganization, since similarly small aftereffects were found when subjects concentrated their attention on a single pattern element.     

Sensorimotor performance as a function of eye dominance and handedness.

Performance on a speeded target striking task was significantly associated with eye dominance and handedness for a sample of 30 subjects. They showed the expected higher performance with the dominant hand but also showed an effect of eye of input. Highest performance was obtained with binocular viewing, next best used the dominant eye, and poorest performance the nondominant eye. Effects were additive with no interaction between hand and eye dominance.     

I Spy With My Dominant Eye

The authors investigated how visual information from the nondominant and dominant eyes are utilized to control ongoing dominant hand movements. Across 2 experiments, participants performed upper-limb pointing movements to a stationary target or an imperceptibly shifted target under monocular-dominant, monocular-nondominant, and binocular viewing conditions. Under monocular-dominant viewing conditions, participants exhibited better endpoint precision and accuracy. On target jump trials, participants spent more time after peak limb velocity and significantly altered their trajectories toward the new target location only when visual information from the dominant eye was available. Overall, the results suggest that the online visuomotor control processes that typically take place under binocular viewing conditions are significantly influenced by input from the dominant eye.     

The effects of environmental changes on one-handed catching

Ball catching involves predicting the time and place of arrival of a mobile object. Visual cues of various kinds may help a ball catcher to perform this task successfully. The aims of the present study were (a) to assess the role of the environment in the spatiotemporal planning of ball-catching movements and (b) to determine what specific cues are actually used for this purpose. In the first experiment described here, subjects' catching performances were compared under four different environmental conditions, namely, normal lighting, ultraviolet light with no background, ultraviolet light with a densely structured background, and ultraviolet light with a sparsely structured background. Our results showed that the sight of the mobile object alone does not provide enough information for a subject to achieve his maximum performance level. Accurately assessing the point of arrival of the ball requires the use of relative visual cues. The environment is also a source of visual cues used to assess the time of arrival of the ball. A second experiment was carried out with a view to determining the exact nature of the visual cues used. Here, the orientation (frontal vs. oblique plane) and the apparent visual angle (6 degrees vs. 42 degrees ) of the background were made to vary. The results of this experiment showed that the orientation of the background affected the percentage of spatial errors produced by the subjects, whereas the apparent visual angle affected the percentage of temporal errors. The relative velocity cue generated by the masking of successive structures in the environment by the oncoming ball seems to have been taking into account in estimating the time of arrival of the ball. This cue seems to be of crucial importance during the 200 ms prior to the time of contact between the ball and the subject's hand. This finding supports the idea that the method used to assess the time to contact may involve velocity information.     

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.     

Phasing and the Pickup of Optical Information in Cascade Juggling

Four experiments were conducted to examine the relationship between the phasing of hand movements and the pickup of optical information in cascade juggling. Three jugglers of intermediate skill juggled three balls while wearing liquid crystal (LC) glasses that opened and closed at preset intervals. The first experiment, in which the duration of the viewing window was gradually reduced to zero, revealed a preference for seeing the segment of the ball flight following the zenith in one subject; such a preference was hinted at in the other two subjects. The second experiment, in which the tachistoscopic rhythm of the glasses was perturbed, showed that, in the case of a stable phase lock, the phasing of the hand movements was adjusted to restore the visibility of the segment following the zenith when it was lost. The third experiment, however, revealed that, after practice, the jugglers did not become better attuned to the optical information contained in this segment. The fourth experiment, in which two jugglers per- formed a cascade together while viewing the ball flights intermittently, suggested that haptic information about the trajectories of the balls to be caught is not necessary for subsequent catching: Optical information picked up during brief intervals of viewing was sufficient to perform the task equally well as when they juggled alone (i.e., when haptic information about the throws was available). Although, admittedly, the results raised only a tip of the veil covering the perceptual basis of juggling, they testify to the potential power of the new technique that was used to let subjects themselves reveal what optical information is relevant for performance.     

Attention affects the stereoscopic depth aftereffect

'Preattentive' vision is typically considered to include several low-level processes, including the perception of depth from binocular disparity and motion parallax. However, doubt was cast on this model when it was shown that a secondary attentional task can modulate the motion aftereffect (Chaudhuri, 1990 Nature 344 60-62). Here we investigate whether attention can also affect the depth aftereffect (Blakemore and Julesz, 1971 Science 171 286-288). Subjects adapted to stationary or moving random-dot patterns segmented into depth planes while attention was manipulated with a secondary task (character processing at parametrically varied rates). We found that the duration of the depth aftereffect can be affected by attentional manipulations, and both its duration and that of the motion aftereffect varied with the difficulty of the secondary task. The results are discussed in the context of dynamic feedback models of vision, and support the penetrability of low-level sensory processes by attentional mechanisms.     

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.     

Interaction between perceived and imagined rotation

In Experiment 1, subjects performed a mental-rotation task in which they were timed as they decided whether rotated letters were normal or backwards. Between presentations of the letters, they watched a rotating textured disk that induced an aftereffect of rotary movement on the letters. The function relating reaction times to orientation was influenced asymmetrically by the aftereffect, suggesting that perceived movement interacts with imagined movement. Experiment 2 showed that the aftereffect produced a negligible influence on perceived orientation, suggesting that the influence of the aftereffect on mental rotation was not caused by changes in the perceived orientations of the letters. Detailed analysis of the mental-rotation functions suggested that the aftereffect may sometimes have induced subjects to rotate letters through the larger rather than the smaller angle back to the upright where the aftereffect was in the appropriate direction.     

Perception of acceleration with short presentation times: can acceleration be used in interception?

To investigate whether visual judgments of acceleration could be used for intercepting moving targets, we determined how well subjects can detect acceleration when the presentation time is short. In a differential judgment task, two dots were presented successively. One dot accelerated and the other decelerated. Subjects had to indicate which of the two accelerated. In an absolute judgment task, subjects had to adjust the motion of a dot so that it appeared to move at a constant velocity. The results for the two tasks were similar. For most subjects, we could determine a detection threshold even when the presentation time was only 300 msec. However, an analysis of these thresholds suggests that subjects did not detect the acceleration itself but that they detected that a target had accelerated on the basis of the change in velocity between the beginning and the end of the presentation. A change of about 25% was needed to detect acceleration with reasonable confidence. Perhaps the simplest use of acceleration for interception consists of distinguishing between acceleration and deceleration of the optic projection of an approaching ball to determine whether one has to run backward or forward to catch it. We examined the results of a real ball-catching task (Oudejans, Michaels, & Bakker, 1997) and found that subjects reacted before acceleration could have been detected. We conclude that acceleration is not used in this simple manner to intercept moving targets.     

Journal of experimental psychology: human perception and performance

We examined the nonveridicality of visual direction produced by monocular viewing. In Experiment 1, 19 subjects pointed to a small light and moved a small light to their subjective median plane. The extent of constant error under monocular and binocular viewing conditions differed in both tasks (p less than .001). The monocular-binocular difference was larger when the viewing distance was 25 cm than when it was 50 cm (p less than .01). Also, correlations between phoria and monocular-binocular differences ranged from .58 to .77, depending on viewing distances and tasks. The effects of phoria within the context of Hering's .001). The monocular-binocular difference was larger when the viewing distance was 25 cm than when it was 50 cm (p less than .01). Also, correlations between phoria and monocular-binocular differences ranged from .58 to .77, depending on viewing distances and tasks. The effects of phoria within the context of Hering's .001). The monocular-binocular difference was larger when the viewing distance was 25 cm than when it was 50 cm (p less than .01). Also, correlations between phoria and monocular-binocular differences ranged from .58 to .77, depending on viewing distances and tasks. The effects of phoria within the context of Hering's principle of visual direction can account for these results. In Experiment 2, the same subjects adapted to phoria-induced error by placing a finger over a monocularly viewed target. The difference in their pointing responses before and after the task were reliable (p less than .005), and the correlations between phoria and the pre- to posttest differences were .45 and .77, depending on the number of adaptation trials. We argue that all monocular experiments dealing with visual direction should control for these effects.