Interception Task Research Articles

Continuous visual control of interception

People generally try to keep their eyes on a moving target that they intend to catch or hit. In the present study we first examined how important it is to do so. We did this by designing two interception tasks that promote different eye movements. In both tasks it was important to be accurate relative to both the moving target and the static environment. We found that performance was more variable in relation to the structure that was not fixated. This suggests that the resolution of visual information that is gathered during the movement is important for continuously improving predictions about critical aspects of the task, such as anticipating where the target will be at some time in the future. If so, variability in performance should increase if the target briefly disappears from view just before being hit, even if the target moves completely predictably. We demonstrate that it does, indicating that new visual information is used to improve precision throughout the movement.

Manipulating informational constraints shapes movement reorganization in interceptive actions

Movement organization of cricket batters' actions was analyzed under three distinct experimental task constraints: a representative condition of a practice context in which the batters batted against a "live" bowler, a ball projection machine, and a near life-size video simulation of a bowler. Results showed that each distinct set of task constraints led to significant variations in the patterns of movement control. Removal of advanced information sources from a bowler's actions when the batters faced the ball projection machine caused significant delays in movement initiation, resulting in reduced peak bat swing velocities and a reduction in the quality of bat-ball contact, when compared with batting against a "live" bowler. When responding to a two-dimensional video simulation, batters were able to use information from the bowlers' action, enabling fidelity of initial behavioral responses consistent with the task of batting against a "live" bowler. However, without interceptive task requirements or actual ball flight information, significant variations in downswing initiation timing and peak bat velocities were demonstrated. Findings stress the need for representative experimental and learning designs in fast ball sports for developing performers.

A new ball launching system with controlled flight parameters for catching experiments

Systematic investigations of sensorimotor control of interceptive actions in naturalistic conditions, such as catching or hitting a ball moving in three-dimensional space, requires precise control of the projectile flight parameters and of the associated visual stimuli. Such control is challenging when air drag cannot be neglected because the mapping of launch parameters into flight parameters cannot be computed analytically. We designed, calibrated, and experimentally validated an actuated launching apparatus that can control the average spatial position and flight duration of a ball at a given distance from a fixed launch location. The apparatus was constructed by mounting a ball launching machine with adjustable delivery speed on an actuated structure capable of changing the spatial orientation of the launch axis while projecting balls through a hole in a screen hiding the apparatus. The calibration procedure relied on tracking the balls with a motion capture system and on approximating the mapping of launch parameters into flight parameters by means of polynomials functions. Polynomials were also used to estimate the variability of the flight parameters. The coefficients of these polynomials were obtained using the launch and flight parameters of 660 launches with 65 different initial conditions. The relative accuracy and precision of the apparatus were larger than 98% for flight times and larger than 96% for ball heights at a distance of 6 m from the screen. Such novel apparatus, by reliably and automatically controlling desired ball flight characteristics without neglecting air drag, allows for a systematic investigation of naturalistic interceptive tasks.

Indirect interception actions by blind and sighted perceivers: The role of modality and tau

Acoustic and visual interceptive actions were tested in this research by comparing the performance of blind, blind-folded, and sighted individuals. An indirect interception method was employed in which the participant had to roll an intercepting ball towards a moving target on a perpendicular track. The interception task used conditions that varied the speed, rolling distance, and target size/intensity. While performance was highly consistent and accurate for visual participants in this research, the blind and blind-folded participants demonstrated much more performance variability in response to changes in speed and distance. Manipulation of target size and intensity did not affect judgments, however performance tended to be more accurate at shorter distances and with faster target speeds. Results from this research are discussed in terms of their implications for tau in acoustic interception, and the use of spatial and temporal cues for guiding interceptive actions.

Are Visual Cue Masking and Removal Techniques Equivalent for Studying Perceptual Skills in Sport?

The spatial-occlusion paradigm makes use of two techniques (masking and removing visual cues) to provide information about the anticipatory cues used by viewers. The visual scene resulting from the removal technique appears to be incongruous, but the assumed equivalence of these two techniques is spreading. The present study was designed to address this issue by combining eye-movement recording with the two types of occlusion (removal versus masking) in a tennis serve-return task. Response accuracy and decision onsets were analysed. The results indicated that subjects had longer reaction times under the removal condition, with an identical proportion of correct responses. Also, the removal technique caused the subjects to rely on atypical search patterns. Our findings suggest that, when the removal technique was used, viewers were unable to systematically count on stored memories to help them accomplish the interception task. The persistent failure to question some of the assumptions about the removal technique in applied visual research is highlighted, and suggestions for continued use of the masking technique are advanced.

The Neural Substrate of Predictive Motor Timing in Spinocerebellar Ataxia

The neural mechanisms involved in motor timing are subcortical, involving mainly cerebellum and basal ganglia. However, the role played by these structures in predictive motor timing is not well understood. Unlike motor timing, which is often tested using rhythm production tasks, predictive motor timing requires visuo-motor coordination in anticipation of a future event, and it is evident in behaviors such as catching a ball or shooting a moving target. We examined the role of the cerebellum and striatum in predictive motor timing in a target interception task in healthy (n = 12) individuals and in subjects (n = 9) with spinocerebellar ataxia types 6 and 8. The performance of the healthy subjects was better than that of the spinocerebellar ataxia. Successful performance in both groups was associated with increased activity in the cerebellum (right dentate nucleus, left uvula (lobule V), and lobule VI), thalamus, and in several cortical areas. The superior performance in the controls was related to activation in thalamus, putamen (lentiform nucleus) and cerebellum (right dentate nucleus and culmen-lobule IV), which were not activated either in the spinocerebellar subjects or within a subgroup of controls who performed poorly. Both the cerebellum and the basal ganglia are necessary for the predictive motor timing. The degeneration of the cerebellum associated with spinocerebellar types 6 and 8 appears to lead to quantitative rather than qualitative deficits in temporal processing. The lack of any areas with greater activity in the spinocerebellar group than in controls suggests that limited functional reorganization occurs in this condition.

Age-related decline in sensory processing for locomotion and interception

The ability to control locomotion through the environment and to intercept, or avoid objects is fundamental to the survival of all locomotor species. The extent to which this control relies upon optic flow, visual direction cues or non-visual sensory inputs has long been debated. Here we look at the use of sensory information in young and middle-aged participants using a locomotor-driven interceptive task. Both groups of participants were asked to produce forward displacements in more or less impoverished environments by manipulating a joystick and to regulate, if necessary, their displacement velocity so as to intercept approaching targets. We show that the displacements produced by the middle-aged participants were more nonlinear in comparison with young participants. The errors in the middle-aged group can be accounted for by a constant bearing angle (CBA) model that incorporates a decrease in the sensitivity of sensory detection with advancing age. The implications of this study to a better understanding of the mechanisms underlying the detection of the rate of change in bearing angle are discussed.

Action specificity increases anticipatory performance and the expert advantage in natural interceptive tasks

The relationship between perception–action coupling and anticipatory skill in an interceptive task was examined using an in-situ temporal occlusion paradigm. Skilled and novice cricket batsmen were required to predict the direction of balls bowled towards them under four counterbalanced response conditions of increasing perception–action coupling: (i) verbal, (ii) lower-body movement only, (iii) full-body movement (no bat), and (iv) full-body movement with bat (i.e., the usual batting response). Skilled but not novice anticipation was found to improve as a function of coupling when responses were based on either no ball-flight, or early ball-flight information, with a response requiring even the lowest degree of body movement found to enhance anticipation when compared to a verbal prediction. Most importantly, a full-body movement using a bat elicited greater anticipation than an equivalent movement with no bat. This result highlights the important role that the requirement and/or opportunity to make bat–ball interception may play in eliciting skill differences for anticipation. Results verify the importance of using experimental conditions and task demands that closely reflect the natural performance environment in order to reveal the full nature of the expert advantage.

An event-related visual occlusion method for examining anticipatory skill in natural interceptive tasks

This article describes a new automated method for the controlled occlusion of vision during natural tasks. The method permits the time course of the presence or absence of visual information to be linked to identifiable events within the task of interest. An example application is presented in which the method is used to examine the ability of cricket batsmen to pick up useful information from the prerelease movement patterns of the opposing bowler. Two key events, separated by a consistent within-action time lag, were identified in the cricket bowling action sequence-namely, the penultimate foot strike prior to ball release (Event 1), and the subsequent moment of ball release (Event 2). Force-plate registration of Event 1 was then used as a trigger to facilitate automated occlusion of vision using liquid crystal occlusion goggles at time points relative to Event 2. Validation demonstrated that, compared with existing approaches that are based on manual triggering, this method of occlusion permitted considerable gains in temporal precision and a reduction in the number of unusable trials. A more efficient and accurate protocol to examine anticipation is produced, while preserving the important natural coupling between perception and action.

Eye movements in a spatially and temporally demanding interception task

Eye movements in a spatially and temporally demanding interception task

A simple empirical law for a class of visually timed interceptive actions

People are highly skilled at intercepting moving objects and capable of remarkably precise timing - in the order of a few milliseconds. The timing of interceptions is constrained by two situational factors: the time available to plan and complete the action and the temporal precision required by the task. Recent research on interceptive actions indicates that a highly replicable relationship is likely to exist between movement timing and task constraints. This is analogous to the classic Fitts' law relationship that relates movement time (MT) to task variables for movements aimed at stationary targets. We report two experiments that allowed a description of the relationship for an anticipatory interception task (without target pursuit). Two quantities that determine the required temporal precision were varied in experiment 1 - target speed and size. Available time (viewing time, VT) was kept constant and relatively large (1.6 s). MT was found to decrease with increases in target speed and decreases in target size. These results conformed to a specific empirical relationship between MT and the task variables. In experiment 2, VT and target speed were varied. MT was found to decrease monotonically with decreases in VT and the effect of target speed declined, becoming undetectable at the shortest VT (0.4s). These results can be interpreted as providing direct information about the 'rule' used by the nervous system to pre-determine MT in anticipatory interceptions.

Planning of an interceptive movement in children

In the present study, we examined the spatio-temporal organization of the walking and reaching behaviour during an interception task in younger (6–9 years old) and older (10–13 years old) children. To this end, eighteen children had to walk towards an interception point to grasp a moving ball under three visual manipulation conditions. Walking and reaching behaviour were analysed during a condition allowing full vision of the ball trajectory and during two conditions in which vision towards the ball was partly occluded (enhanced planning requirement). The velocity of the ball was adapted to 50 or 70% of the maximum walking velocity of the participant. Results revealed that both younger and older children show a less accurate performance when the ball trajectory was occluded, while the walking profile and timing of the reach was not influenced by the occlusion manipulations. The findings seem to suggest that both groups were less accurate when the necessity of planning was enhanced.

Emergent flexibility in motor learning

We examined the effect of exploring redundant solutions during practice in enhancing the ability to flexibly use them to achieve a task goal. Three groups used different degrees of path redundancy to perform a virtual interception task in which they attempted to hit a stationary target by moving around a stationary obstacle. The low-variability group always practiced with the same position of the obstacle on all trials. The medium-variability and high-variability groups practiced with the obstacle in different positions within a range of 1 and 2 cm respectively. After eight blocks of practice, all participants were transferred to two tests: (a) a fixed obstacle test where the condition was the same as that practiced by the low-variability group, and (b) a variable obstacle test where the condition was the same as that practiced by the high-variability group. Results showed that the low-variability group had the most accurate performance both in the fixed obstacle and the variable obstacle test. The low-variability group showed the least path variability during the fixed obstacle test but was also able to adapt to the different positions of the obstacle during the variable obstacle test. It appears that flexibility in interceptive tasks is emergent from learning a particular task-relevant parameter related to the target location.

Visuo-motor delay, information–movement coupling, and expertise in ball sports

We compared the performance of tennis experts and non-experts using a simulated interceptive task, in which the ball could be unexpectedly deviated 400 ms before contact. The results showed that experts were more accurate than non-experts when intercepting balls that deviated in their trajectory and that this could be explained by their shorter visuo-motor delay in adapting their interceptive movement. In addition, multiple regression analyses revealed that visuo-motor delay was a good predictor of accuracy in this task. Finally, accuracy in the simulated interceptive task was shown to be a reasonable predictor of expertise in tennis assessed by national ranking. In combination, the present results suggest that an important component of expertise in interceptive skills is fast information–movement coupling, which corresponds to a reduced delay in integrating vision and action. Our findings highlight the potential of the virtual interceptive task used here to predict performance in tennis.

Influence of motor learning on utilizing path redundancy

We examined the role of motor learning in influencing the utilization of path redundancy in an interception task. Participants used a pen on a digitizing tablet with the goal of moving to intercept a stationary target shown on a computer screen. Concurrent visual feedback of the cursor and knowledge of results were provided. The changes in spatial variability after extended practice and the correlations between spatial locations on the path were consistent with the view that path redundancy was utilized. However, paths also became less variable with practice, indicating that less of the solution space was utilized. There was also a sequential relation in the movement paths from trial to trial with a tendency to use more similar movement paths on successive trials. These results show that models that account for both redundancy and invariance may be better able to capture the changes in variability with learning. Further, the sequential dependence in the paths suggests that the exploration of redundant solutions is a systematic search process.

Brain activity preceding a 2D manual catching task

We investigated the event-related desynchronization (ERD) and synchronization (ERS) properties of cortical EEG rhythms in regions of interest (ROI) during the preparation of a 2D task for manual catching of a moving object. EEG signals were recorded through a 32-channel system in eleven healthy subjects during the interception task consisting of 2D catching with the right hand of a handle moving at constant velocity (1.5 m/s) on a predefined straight trajectory. The first session of catching movements (CATCHING_PRE) was compared with a second session after 1 h with identical characteristics (CATCHING_POST) and with other two conditions, where the subjects had to reach and grasp the handle fixed in the medium of platform (REACHING) and they looked at the object moving without catching it (GAZE TRACKING). Changes of cortical rhythms were correlated with dynamic and kinematic indexes of motor performance in both catching sessions.Movements requiring different strategies (predictive versus prospective) are supported by specific changes of cortical EEG rhythms: in the CATCHING condition a more evident power decrease (ERD) in alpha 2 and beta band in the sensorimotor region contralateral to the catching hand was observed, while in the REACHING one a bilateral ERD in beta band was found. Motor learning and movement automatization were characterized by a significant reduction of theta ERS in the anterior cingulate cortex (ACC), a ROI linked to focused attention, and with a shift of neuronal activation in alpha 2 band from the bilateral superior parietal areas to the homologous area of the left hemisphere. Finally, our EEG findings are consistent with the role of supplementary motor (SMA), premotor and prefrontal areas in motor planning and preparation. In particular, theta ERS in left SMA significantly correlated with an improvement of motor performance, as evidenced by its correlation with the training-related reduction of interception time (IT).

Greater Specificity of Sensorimotor Learning in the Elderly When Acquiring an Interceptive Task

In this investigation we assessed the extent to which young and elderly individuals become dependent on the specific visual situation present during practice of an interceptive task. Young and elderly participants practiced extensively a task of intercepting a virtually moving target under full vision or visual occlusion of the last 600 ms of target displacement. Before and after practice they were assessed in four visual conditions varying the time interval of visual display. The results showed that the elderly practicing under full vision had a progressive increase of temporal errors as a function of the period of visual occlusion after task acquisition. The elderly practicing under visual occlusion, conversely, achieved improved performance only in the visual condition experienced during task acquisition. Young individuals showed greater adaptability, presenting similar performance across visual conditions. Development of specific visuomotor integration only for the elderly seems to be related with the higher status that vision holds for movement control at this age.

Greater Specificity of Sensorimotor Learning in the Elderly When Acquiring an Interceptive Task

Greater Specificity of Sensorimotor Learning in the Elderly When Acquiring an Interceptive Task

Manual interception of moving targets in two dimensions: Performance and space-time accuracy

We report results from four experiments that examined performance of an interceptive task that restricted movement of the hand and moving target to a horizontal plane. The task required accurate control over both where and when interception takes place. Three experiments studied the effects of four independent variables: target speed, target size, manipulandum size and movement amplitude. For small amplitude movements, small, fast targets were hit harder than larger slower ones and targets were hit harder with smaller manipulanda; movement time (MT) was unaffected by target size, but was shorter when the manipulandum was smaller. For larger amplitude movements, smaller, faster targets were also hit harder, but MTs tended to be greater when targets were smaller. The results support the idea that MT and peak movement speed can be independently controlled to some degree in order to meet the accuracy demands of the task. Analysis of the task showed that spatial and temporal accuracy demands are interdependent, indicating that the spatial and temporal variable errors should covary such that increases in one are accompanied by decreases in the other. This can be tested if there is no variation in interception location; which was not the case in the first three experiments. In a final experiment variation in interception location was restricted by requiring that the target be struck through an aperture. Both spatial and temporal variable errors could be estimated. As predicted, it was found that when spatial errors were small, temporal errors were large.

Evidence for a generic interceptive strategy

In the present work, we first clarify a more precise definition of instantaneous optical angles in control tasks such as interception. We then test how well two interceptive strategies that have been proposed for catching fly balls account for human Frisbee-catching behavior. The first strategy is to maintain the ball's image along a linear optical trajectory (LOT). The second is to keep vertical optical ball velocity decreasing while maintaining constant lateral optical velocity. We found that an LOT accounted for an average of over 96% of the variance in optical Frisbee movement, while maintenance of vertical and lateral optical velocities was random. This work confirms a common interception strategy used across interceptive tasks, extending to complex target trajectories.