Role of Visual Information in Ball Catching

The present study is concerned with the perceptual information about the body and space underlying the act of catching a ball. In a series of four experiments, subjects were asked to catch a luminous ball under various visual conditions. In general, catching in a normally illuminated room was contrasted with catching the luminous ball in an otherwise completely dark room. In the third and fourth experiments, intermediate conditions of visual information were included. The results suggest that it is possible to catch a ball with one hand when only the ball is visible, but performance is better when the subject has the benefit of a rich visual environment and two hands. The second experiment indicated that subject performance does improve with practice in the dark, but time spent in the darkened room itself doesn't result in a significant decrement in performance. Results of the third study suggest that vision of one's hand does not aid in the performance of this task whereas the presence of a minimal visual frame appears to aid performance. The final study examined the relation between catching performance and body sway under similar visual conditions. Results of this experiment imply that persons who exhibit relatively little postural sway in full-room lighting performed better at this catching task.     

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.     

Planning and on-line control of catching as a function of perceptual-motor constraints

Two experiments were conducted in order to investigate the adaptability and associated strategies of the human perceptuo-motor system to deal with changing constraints. In a catching task, perceptual-motor constraints were internally controlled by coupling movement onset of the catch and the illumination circuit in the lab: upon the first movement of the catcher, all lights went out within 3 ms. The authors studied (a) how much movement time catchers prefer if no visual information is available after movement onset, and (b) how movement execution changes under such temporal constraints. It was hypothesised that, in order to accomplish successful catching behaviour, (1) movement initiation would be postponed in order to allow sufficient information uptake before the lights went out, and (2) an alternative control strategy would have to be mobilised, since on-line control becomes inappropriate when catching in the dark. In the first experiment, the adaptation process to the light-dark paradigm was investigated. In the second experiment, the conclusions from experiment 1 were challenged under varying ball speeds. In order to maintain catching performance, subjects initiated the catch approximately 280 ms before ball-hand contact. Next to changes in temporal structure of the catch and subtle kinematic adaptations, evidence for a change in the control mode emerged: while an on-line control strategy was adopted under normal illumination, catching movements seemed to be executed as planned in advance when catching in the dark. Additionally, perceptual constraints seem to determine the time of movement initiation, rather than motor constraints. These results emphasize the capability of the human perceptuo-motor system to adjust promptly to new task constraints.     

Spatial and temporal adaptations that accompany increasing catching performance during learning

The authors studied changes in performance and kinematics during the acquisition of a 1-handed catch. Participants were 8 women who took an intensive 2-week training program during which they evolved from poor catchers to subexpert catchers. An increased temporal consistency, shift in spatial location of ball-hand contact away from the body, and higher peak velocity of the transport of the hand toward the ball accompanied their improvement in catching performance. Moreover, novice catchers first adjusted spatial characteristics of the catch to the task constraints and fine-tuned temporal features only later during learning. A principal components analysis on a large set of kinematic variables indicated that a successful catch depends on (a) forward displacement of the hand and (b) the dynamics of the hand closure, thereby providing a kinematic underpinning for the traditional transport-manipulation dissociation in the grasping and catching literature.     

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.     

Did you see that? Dissociating advanced visual information and ball flight constrains perception and action processes during one-handed catching

The integration of separate, yet complimentary, cortical pathways appears to play a role in visual perception and action when intercepting objects. The ventral system is responsible for object recognition and identification, while the dorsal system facilitates continuous regulation of action. This dual-system model implies that empirically manipulating different visual information sources during performance of an interceptive action might lead to the emergence of distinct gaze and movement pattern profiles. To test this idea, we recorded hand kinematics and eye movements of participants as they attempted to catch balls projected from a novel apparatus that synchronised or de-synchronised accompanying video images of a throwing action and ball trajectory. Results revealed that ball catching performance was less successful when patterns of hand movements and gaze behaviours were constrained by the absence of advanced perceptual information from the thrower's actions. Under these task constraints, participants began tracking the ball later, followed less of its trajectory, and adapted their actions by initiating movements later and moving the hand faster. There were no performance differences when the throwing action image and ball speed were synchronised or de-synchronised since hand movements were closely linked to information from ball trajectory. Results are interpreted relative to the two-visual system hypothesis, demonstrating that accurate interception requires integration of advanced visual information from kinematics of the throwing action and from ball flight trajectory.     

Vision and proprioception in simple catching

Articular proprioception is normally considered to provide accurate information about limb position, particularly in ball skills in which the eyes are be occupied with tracking the ball. If this is so, then preventing sight of the catching hand without interfering with visual tracking of the ball should affect the accuracy of catching. The experiment reported here indicates that is not the case. Catching is much less accurate if the hand cannot be seen. The errors made are in positioning of the catching hand, which frequently does not contact the ball. In addition, subjects showed larger changes in the felt length arms after catching without sight of the hand than did those who could hand while catching. Visual information about the position of the hand for catching, and this may be because the proprioceptive system is by vision.     

How infants use perceptual information to guide action

When infants catch a rolling ball by intercepting its trajectory, the action is prospectively controlled to take account of the object's speed, direction and path. We complicated this task in two ways: by occluding a portion of the ball's path with a screen, and by sometimes placing a barrier that blocked the ball's path behind the screen. In two experiments we manipulated visual information about the barrier and the ball's trajectory to see how this would aid 9‐month‐olds’ performance. Anticipatory reaching was possible but difficult with a partially occluded trajectory; actually catching the ball was aided by full view of the trajectory although timing of reach onset was not affected. Full sight of the barrier and trajectory through a transparent screen prevented inappropriate reaching, whereas sight of the barrier alone through a ‘window’ in an opaque screen did not. We interpreted these results as evidence for decreased performance as cognitive load increased with the loss of visual information. In contrast to anticipatory reaching behavior, search for the ball after it disappeared behind the screen was facilitated by the opaque window condition, confirming previous studies that found superior search with opaque versus transparent screens.     

Dynamic Visual Acuity

Forty subjects took part in a one-handed catching task in which the period for which the mechanically projected tennis ball was illuminated in flight was varied systematically. Additionally, they were tested for (a) static visual acuity and (b) dynamic visual acuity, in which angular velocity was varied. As expected, both viewing period in the catching task and angular velocity in the acuity task were significant variables in performance. Correlation and principal-components analyses confirmed the findings of a previous experiment in that the correlated static visual acuity tasks were unrelated to both dynamic visual acuity (even when angular velocity was only 75°/sec) and catching performance. Further, dynamic acuity and catching were related under the majority of the combinations, and most frequently at the highest angular velocity, a fact which suggested that the dynamic element in both tasks is the common factor.     

Dynamic visual acuity: a possible factor in catching performance

Forty subjects took part in a one-handed catching ask in which the period for which the mechanically projected tennis ball was illuminated in flight was varied systematically. Additionally, they were tested for (a) static visual acuity and (b) dynamic visual acuity, in which angular velocity was varied. As expected, both viewing period in the catching task and angular velocity in the acuity task were significant variables in performance. Correlation and principal-components analyses confirmed the findings of a previous experiment in that the correlated static visual acuity tasks were unrelated to both dynamic visual acuity (even when angular velocity was only 75 degrees /sec) and catching performance. Further, dynamic acuity and catching were related under the majority of the combinations, and most frequently at the highest angular velocity, a fact which suggested that the dynamic element in both tasks is the common factor.     

Task demand effects on postural control in older adults

The literature shows conflicting results regarding older adults' (OA) postural control performance. Differing task demands amongst scientific studies may contribute to such ambiguous results. Therefore, the purpose of this study was to examine the performance of postural control in older adults and the relationship between visual information and body sway as a function of task demands. Old and young adults (YA) maintained an upright stance on different bases of support (normal, tandem and reduced), both with and without vision, and both with and without room movement. In the more demanding tasks, the older adults displayed greater body sway than the younger adults and older adults were more influenced by the manipulation of the visual information due to the room movement. However, in the normal support condition, the influence of the moving room was similar for the two groups. These results suggest that task demand is an important aspect to consider when examining postural control in older adults.     

Comparison of implicit and explicit learning processes in a probabilistic task

This experiment compared the performance with explicit (rule-application and rule-discovery) and implicit (nonrule-instructed) learning approaches on the performance of a probabilistic video game task requiring fine motor control. The task required visual tracking of a small ball of light and "catching" it by means of joystick manipulation. A general pattern of improvement with practice occurred for all conditions. All conditions showed use of predictive relations among stimulus events. However, task performance of the rule-application and rule-discovery conditions were inferior to the nonrule-instructed implicit condition, particularly during the early phases of rule acquisition and application. This pattern strongly suggests substantial performance costs associated with attempting to discover or apply probabilistic rules. Decrements are likely due to increased cognitive demands associated with attempting to remember and strategically apply provided probability rules or attempting to discover and apply potentially important and useful probability information from a complex visual display.     

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.     

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.     

Developmental differences in the use of peripheral vision during catching performance

Recently, it has been argued that peripheral vision may control adequate orientation of catching limbs, although questions have been raised of whether this remains the case as skill develops. The aim of the present study was to remediate previous methodological deficiencies to verify whether developmental differences exist in the extent of the functional visual field. A further aim included examining the importance of peripheral vision as a control process for effector orientation during catching without recourse to an occlusion technique. Previous arguments that peripheral vision may be necessary in controlling one-handed catching performance were extended to a two-handed catching task. Male subjects (n = 80) were required to perform a two-handed catch and simultaneously process a peripheral visual signal presented either early in, in the middle of, or late in flight. Developmental differences were noted between the age groups (mean ages = 10, 12, 16, and 20 years) in the ability to divide visual attention between the ball in flight, location of hands, and the peripheral cue acting as a probe. Evidently, the ability to allocate control of effects to the articular proprioceptive system develops with age because there was an obvious improvement in peripheral visual processing performance during the late segment of flight. Specifically, it appears that between the ages of 12 and 15 years catchers develop the capacity to increase the functional control of the articular proprioceptive system, as indicated by a significant decrease in peripheral visual errors during the late segment made by the latter age group. Limited evidence is also presented suggesting that the successful allocation of greater control to the articular proprioceptive system changes as a function of practice and experience with the specific central task, thus overcoming initial reliance on sight of the catching hands.     

Implicit versus explicit learning processes in a probabilistic, continuous fine-motor catching task

We compared the influences of explicit instruction and uninstructed implicit learning of correlations among visual events, in a fine-motor task. The task required visual tracking of a small "ball" of light and "catching" it by means of joystick manipulation. A general pattern of improvement with practice for instructed and "noninstructed" conditions was found. Additionally, both instructed and noninstructed conditions evidenced use of the predictive relationships among stimulus events. The improvement in overall performance caused by explicit verbal instructions was less than the improvement seen with the implicit learning condition. Further, instructed and noninstructed conditions showed different patterns of joystick activity. These findings suggest a qualitatively different approach to visual information processing and task performance for the instructional conditions     

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.     

A common first-order time-to-contact based control of hand-closure initiation in catching and grasping

To catch or grasp an object, the initiation of hand closure has to be coordinated with the relative movement between hand and object. In search of a common control of the initiation of hand closure for both tasks (van de Kamp, Bongers, & Zaal, 2010), the authors studied two tasks, catching while keeping the hand stationary and prehension. They showed that the initiation of hand closure could well be based on first-order time-to-contact in the prehension task but not in the catching task studied. The current study tested if the fact that the hand-object gap was closed at a linear rate made that the initiation of hand closure could not be explained on the basis of that same first-order time-to-contact in the catching task. In Experiment 1, the participants had to catch targets that approached at nonlinear rates while keeping the hand stationary. In Experiment 2, the participants were free to move their hand in catching the approaching objects, allowing the closure of the hand-object gap to occur at a nonlinear rate as it would in natural movements. The results showed that the first-order time-to-contact based control of the initiation of hand closure did apply in Experiment 2, whereas it did not in Experiment 1. It was concluded that constraining the catching task such that it became unfamiliar led to a hampered timing, thus obstructing the finding of the common control in the previous study, and in Experiment 1 of the current study.     

I Lost It in the Lights: The Effects of Predictable and Variable Intermittent Vision on Unimanual Catching

In this study, 2 competing views of interceptive action were examined by assessing the influence of variability in the interval between visual samples in a unimanual ball-catching task. Subjects were required to catch tennis balls projected over a distance of 14 m, under conditions of intermittent vision in which the between-sample intervals were either predictable or unpredictable. Results indicated that, although performance was best with shorter between-sample intervals, the temporal predictability of samples did not reliably affect catching performance. This suggests that between-sample retinal expansion provides sufficient information for the timing of the interceptive act.