Temporal precision of interceptive action: differential effects of target size and speed

Sensorimotor ability and inhibitory control independently predict attainment in mathematics in children and adolescents

We previously linked interceptive timing performance to mathematics attainment in 5- to 11-yr-old children, which we attributed to the neural overlap between spatiotemporal and numerical operations. This explanation implies that the relationship should persist through the teenage years. Here, we replicated this finding in adolescents (n = 200, 11-15 yr). However, an alternative explanation is that sensorimotor proficiency and academic attainment are both consequences of executive function. To assess this competing hypothesis, we developed a measure of a core executive function, inhibitory control, from the kinematic data. We combined our new adolescent data with the original children's data (total n = 568), performing a novel analysis controlling for our marker of executive function. We found that the relationship between mathematics and interceptive timing persisted at all ages. These results suggest a distinct functional link between interceptive timing and mathematics that operates independently of our measure of executive function.NEW & NOTEWORTHY Previous research downplays the role of sensorimotor skills in the development of higher-order cognitive domains such as mathematics: using inadequate sensorimotor measures, differences in "executive function" account for any shared variance. Utilizing a high-resolution, kinematic measure of a sensorimotor skill previously linked to mathematics attainment, we show that inhibitory control alone cannot account for this relationship. The practical implication is that the development of children's sensorimotor skills must be considered in their intellectual development.

Estimations of the Passing Height of Approaching Objects

SIGNIFICANCE

Limited optical cues associated with ball flight were inadequate to estimate the vertical passing distance of approaching balls. These results suggest that these optical cues either must be integrated with contextual and kinematic cues or must be of larger amplitude to contribute to estimates of vertical passing distance.

PURPOSE

To intercept or avoid approaching objects, individuals must estimate both when and where the object will arrive. The purpose of this experiment was to determine whether individuals could estimate the vertical passing height of a ball approaching at different linear speeds when vertical angular retinal image velocity and cues for time to contact were minimized.

METHODS

Twenty participants stood 40 feet from a pitching machine that projected tennis balls toward observers at six random speeds from 56 to 80 mph. The flight of the balls was stopped after 9 feet. The actual passing height ranged from about 35 (lowest speed) to 136 cm (highest speed). Observers indicated the height at which they expected the balls to arrive. Overall, the height estimates increased as ball speed increased (means, 121 ± 13 cm [lowest speed] and 131 ± 10 cm [highest speed]). However, only at the higher speeds were the absolute height estimates close to the actual height of the ball. At the higher ball speeds, estimates for participants with some experience in baseball or softball were more accurate (86.4% correct at the highest speed) than estimates for participants with no experience.

CONCLUSIONS

Overall, estimates of vertical passing distance were inaccurate particularly at the lower speeds. Underestimates of vertical drop at lower speeds may have resulted from overestimates of ball speeds. At short exposure durations, optical cues associated with ball flight were inadequate for predictions of vertical passing distance at all speeds for the no-experience group and at lower speeds for the experienced group.

Effects of visual blur and contrast on spatial and temporal precision in manual interception

The visual system is said to be especially sensitive towards spatial but lesser so towards temporal information. To test this, in two experiments, we systematically reduced the acuity and contrast of a visual stimulus and examined the impact on spatial and temporal precision (and accuracy) in a manual interception task. In Experiment 1, we blurred a virtual, to-be-intercepted moving circle (ball). Participants were asked to indicate (i.e., finger tap) on a touchscreen where and when the virtual ball crossed a ground line. As a measure of spatial and temporal accuracy and precision, we analyzed the constant and variable errors, respectively. With increasing blur, the spatial and temporal variable error, as well as the spatial constant error increased, while the temporal constant error decreased. Because in the first experiment, blur was potentially confounded with contrast, in Experiment 2, we re-ran the experiment with one difference: instead of blur, we included five levels of contrast matched to the blur levels. We found no systematic effects of contrast. Our findings confirm that blurring vision decreases spatial precision and accuracy and that the effects were not mediated by concomitant changes in contrast. However, blurring vision also affected temporal precision and accuracy, thereby questioning the generalizability of the theoretical predictions to the applied interception task.

Enhanced Performance Stabilization Increases Performance Variability in a Virtual Interception Task

Performing a motor task depends on the level of performance stabilization and movement control, and both aspects of motor behavior are related to motor learning (retention and transfer) and adaptation (predictable and unpredictable perturbations). Yet few studies have further investigated the underlying dynamics that may elicit these benefits. In this study, we investigated the effects of two levels of performance stabilization on motor performance and control while learning to intercept a virtual moving target. We randomly divided 40 participants of both sexes (M_age = 26.02 years, SD = 2.02) into a Stabilization Group (SG) and a Superstabilization Group (SSG). We considered the performance stabilized when a moving target was intercepted three times in a row and superstabilized when the same criterion was repeated six times. We analyzed outcome variables related to performance accuracy (absolute spatial error) and variability(coefficient of variation) and motor control (relative time to peak velocity-tPV% and its coefficient of variation) on both the first and last blocks of practice trials. Both groups showed comparable increases in performance accuracy from the first to the last block (p = .001, η_p² = 1.00), but SSG presented higher variability than SG (p = .05, η_p² = .70). Concerning motor control, both groups started the experiment with low tPV% and finished with comparably high tPV% and variability. Thus, although practicing two levels of performance stabilization led to similar performance accuracy and movement control, superstabilization resulted in higher performance variability with no loss of accuracy. Enhanced stabilization may increase the ability to adapt to environmental changes, but more research is needed to demonstrate this. These findings add to an understanding of the relationship between levels of performance stabilization and performance variability and may have implications for professional interventions (e.g. sports, rehabilitation) in considering the benefits of practice beyond performance stabilization.

Served Well? A Pilot Field Study on the Effects of Conveying Self-control Strategies on Volleyball Service Performance

Volleyball serves constitute an important example for a self-controlled sequence of actions in sports that is difficult to improve. It is therefore paramount to investigate whether and how conveying self-control strategies to athletes affects their service performance. To address this question, we conducted a pilot field study with sixty-two players from four Swiss volleyball schools. They performed a warm-up and subsequently a first series of 15 serves. Objective service performance was measured in terms of errors, velocity, and precision. Afterwards, players formulated either individual goals (goal condition) or plans (plan condition) based on their coaches’ correction instructions. In a second series of 15 serves objective performance was worse in some respects compared to the first series (i.e., more errors in the plan condition, reduced precision in both conditions). Mixed-effects analyses of performance development across conditions in the second series showed initially reduced but steadily recouping precision and velocity, while the number of errors stayed constant. In contrast to the objective performance, coaches evaluated their players’ service performance during the second series of serves as substantially better than during the first series. Taken together, the results of this pilot field study suggest that conveying either goals or plans as self-control strategies may involve initial adjustment costs followed by a subsequent recovery period.

Continuously updating one’s predictions underlies successful interception

This paper reviews our understanding of the interception of moving objects. Interception is a demanding task that requires both spatial and temporal precision. The required precision must be achieved on the basis of imprecise and sometimes biased sensory information. We argue that people make precise interceptive movements by continuously adjusting their movements. Initial estimates of how the movement should progress can be quite inaccurate. As the movement evolves, the estimate of how the rest of the movement should progress gradually becomes more reliable as prediction is replaced by sensory information about the progress of the movement. The improvement is particularly important when things do not progress as anticipated. Constantly adjusting one’s estimate of how the movement should progress combines the opportunity to move in a way that one anticipates will best meet the task demands with correcting for any errors in such anticipation. The fact that the ongoing movement might have to be adjusted can be considered when determining how to move, and any systematic anticipation errors can be corrected on the basis of the outcome of earlier actions.

Comparing three portable, tablet-based visuomotor tasks to laboratory versions: An assessment of test validity

The assessment of visuomotor function can provide important information about neurological status. Many tasks exist for testing visuomotor function in the laboratory, but the availability of portable, easy-to-use versions that allow reliable, accurate, and precise measurement of movement timing and accuracy has been limited. We developed a tablet application that uses three laboratory visuomotor tests: the double-step task, interception task, and stop-signal task. We asked the participants to perform both the lab and tablet versions of each task and compared their response patterns across equipment types to assess the validity of the tablet versions. On the double-step task, the participants adjusted to the displaced target adequately in both the lab and tablet versions. On the interception task, the participants intercepted nonaccelerating targets and performed worse on accelerating targets in both versions of the task. On the stop-signal task, the participants successfully inhibited their reaching movements on short stop-signal delays (50–150 ms) more frequently than on long stop-signal delays (200 ms) in both versions of the task. Our findings suggest that the tablet version of each task assesses visuomotor processing in the same way as their respective laboratory version, thus providing the research community with a new tool to assess visuomotor function.

Intercepting accelerated moving targets: effects of practice on movement performance

When performing a rapid manual interception, targets moving under constant motion are often intercepted with greater accuracy when compared to targets moving under accelerated motion. Usually, accelerated targets are timed too late and decelerating ones too early. The present experiment sought to investigate whether these differences in performance when intercepting targets moving under constant and accelerated motions change after a short period of practice. The task involved striking targets that moved along a straight track by moving forward a manipulandum that moved along a slide perpendicular to the target's motion. Participants were allocated to one of the three experimental groups, defined according to the type of motion of the moving targets: constant speed, constant acceleration, and constant deceleration. Results showed that after some practice participants were able to intercept (positive and negative) accelerating moving targets as accurately as constant speed targets. These results suggest that people might be able to learn how to intercept accelerating targets, corroborating the results of some recent studies.

Interpersonal variability in timing strategy and temporal accuracy in rapid interception task with variable time-to-contact

In rapid interceptive actions such as hitting a baseball, cricket ball or tennis ball, ball speed varies between trials, and players have to compensate the time lag by controlling the moment of movement onset and movement duration. Previous studies have found that these two variables can flexibly co-vary and are robustly influenced by target speed (i.e. velocity-coupling effect: faster movement for faster target). However, some studies reported an interpersonal variability in the timing control strategy and the relationship between the strategy and temporal accuracy in rapid interception is unclear. We used a baseball-simulated rapid interceptive task to assess this issue. Under relatively easy time constraints, there was a large interpersonal variability, and participants were distinctively divided into two groups: those who mainly modulated their movement duration and those who mainly controlled their movement onset. When the time constraint became severe, the second strategy shifted to the first strategy in most of the second group participants. In the both cases, being able to mainly control movement onset resulted in higher temporal accuracy. These results suggest that minimising the velocity-coupling effect is an important factor to achieve high temporal accuracy in rapid interception.

Precise timing when hitting falling balls

People are extremely good at hitting falling balls with a baseball bat. Despite the ball's constant acceleration, they have been reported to time hits with a standard deviation of only about 7 ms. To examine how people achieve such precision, we compared performance when there were no added restrictions, with performance when looking with one eye, when vision was blurred, and when various parts of the ball's trajectory were hidden from view. We also examined how the size of the ball and varying the height from which it was dropped influenced temporal precision. Temporal precision did not become worse when vision was blurred, when the ball was smaller, or when balls falling from different heights were randomly interleaved. The disadvantage of closing one eye did not exceed expectations from removing one of two independent estimates. Precision was higher for slower balls, but only if the ball being slower meant that one saw it longer before the hit. It was particularly important to see the ball while swinging the bat. Together, these findings suggest that people time their hits so precisely by using the changing elevation throughout the swing to adjust the bat's movement to that of the ball.

How the required precision influences the way we intercept a moving object

Do people perform a given motor task differently if it is easy than if it is difficult? To find out, we asked subjects to intercept moving virtual targets by tapping on them with their fingers. We examined how their behaviour depended on the required precision. Everything about the task was the same on all trials except the extent to which the fingertip and target had to overlap for the target to be considered hit. The target disappeared with a sound if it was hit and deflected away from the fingertip if it was missed. In separate sessions, the required precision was varied from being quite lenient about the required overlap to being very demanding. Requiring a higher precision obviously decreased the number of targets that were hit, but it did not reduce the variability in where the subjects tapped with respect to the target. Requiring a higher precision reduced the systematic deviations from landing at the target centre and the lag-one autocorrelation in such deviations, presumably because subjects received information about smaller deviations from hitting the target centre. We found no evidence for lasting effects of training with a certain required precision. All the results can be reproduced with a model in which the precision of individual movements is independent of the required precision, and in which feedback associated with missing the target is used to reduce systematic errors. We conclude that people do not approach this motor task differently when it is easy than when it is difficult.

Hitting a cricket ball: what components of the interceptive action are most linked to expertise?

Differences in interceptive skill between highly skilled and lesser skilled cricket batsmen were examined using a batting task that required participants to strike front-foot drive strokes from a machine-projected ball to a specified target. Task difficulty was manipulated by varying the width of the bat (normal, half, and third width) and target accuracy, and quality of bat-ball contact was monitored along with temporal and sequential elements of the hitting action. Analyses revealed that the highly skilled batsmen were distinguishable from less skilled counterparts by their higher accuracy under the normal and half-width bat conditions, significantly earlier initiation and completion of the front-foot stride, greater synchronization of the completion of the front-foot stride with the commencement of the downswing of the bat, and consistent timing of downswing relative to ball bounce and impact. In keeping with studies of other hitting sports, temporal and spatial coupling of the downswing to ball bounce to help minimize temporo-spatial error at the point of interception appeared critical to skilled performance. Implications for the understanding of interception and for coaching practice are briefly discussed.

Eye movements influence estimation of time-to-contact in prediction motion

In many situations, it is necessary to predict when a moving object will reach a given target even though the object may be partially or entirely occluded. Typically, one would track the moving object with eye movements, but it remains unclear whether ocular pursuit facilitates accurate estimation of time-to-contact (TTC). The present study examined this issue using a prediction-motion (PM) task in which independent groups estimated TTC in a condition that required fixation on the arrival location as an object approached, or a condition in which participants were instructed to pursue the moving object. The design included 15 TTC ranging from 0.4 to 1.5 s and three object velocities (2.5, 5, 10 deg/s). Both constant error and variable error in TTC estimation increased as a function of actual TTC. However, for the fixation group only, there was a significant effect of object velocity with a relative overestimation of TTC for the slower velocity and underestimation for the faster velocity. Further analysis indicated that the velocity effect exhibited by the fixation group was consistent with participants exhibiting a relatively constant misperception for each level of object velocity. Overall, these findings show that there is an advantage in the PM task to track the moving object with the eyes. We explain the different pattern of TTC estimation error exhibited when fixating and during pursuit with reference to differences in the available retinal and/or extra-retinal input.

Indirect interception actions by blind and visually impaired perceivers: echolocation for interceptive actions

This research examined the acoustic information used to support interceptive actions by the blind. Congenitally blind and severely visually impaired participants (all wearing an opaque, black eye-mask) were asked to listen to a target ball rolling down a track. In response, participants rolled their own ball along a perpendicular path to intercept the target. To better understand what information was used the echoic conditions and rolling dynamics of the target were varied across test sessions. In addition the rolling speed of the target and the distance of the participant from the target were varied across trials. Results demonstrated that participants tended to perform most accurately at moderate speeds and distances, overestimating the target's arrival at the fastest speed, and underestimating it at the slowest speed. However, changes to the target's dynamics, that is, the amount of deceleration it underwent on approach, did not strongly influence performance. Echoic conditions were found to affect performance, as participants were slightly more accurate in conditions with faster, higher-intensity echoes. Based on these results blind individuals in this research seemed to be using spatial and temporal cues to coordinate their interceptive actions.

Behavioral and neurophysiological aspects of target interception

This chapter focuses on the behavioral and neurophysiological aspects of manual interception. We review the most important elements of an interceptive action from the sensory and cognitive stage to the motor side of this behavior. We describe different spatial and temporal target parameters that can be used to control the interception movement, as well as the different strategies used by the subject to intercept a moving target. We review the neurophysiological properties of the parietofrontal system during target motion processing and during a particular experiment of target interception. Finally, we describe the neural responses associated with the temporal and spatial parameters of a moving target and the possible neurophysiological mechanisms used to integrate this information in order to trigger an interception movement.

Systematic changes in the duration and precision of interception in response to variation of amplitude and effector size

The results of two experiments are reported that examined how performance in a simple interceptive action (hitting a moving target) was influenced by the speed of the target, the size of the intercepting effector and the distance moved to make the interception. In Experiment 1, target speed and the width of the intercepting manipulandum (bat) were varied. The hypothesis that people make briefer movements, when the temporal accuracy and precision demands of the task are high, predicts that bat width and target speed will divisively interact in their effect on movement time (MT) and that shorter MTs will be associated with a smaller temporal variable error (VE). An alternative hypothesis that people initiate movement when the rate of expansion (ROE) of the target's image reaches a specific, fixed criterion value predicts that bat width will have no effect on MT. The results supported the first hypothesis: a statistically reliable interaction of the predicted form was obtained and the temporal VE was smaller for briefer movements. In Experiment 2, distance to move and target speed were varied. MT increased in direct proportion to distance and there was a divisive interaction between distance and speed; as in Experiment 1, temporal VE was smaller for briefer movements. The pattern of results could not be explained by the strategy of initiating movement at a fixed value of the ROE or at a fixed value of any other perceptual variable potentially available for initiating movement. It is argued that the results support pre-programming of MT with movement initiated when the target's time to arrival at the interception location reaches a criterion value that is matched to the pre-programmed MT. The data supported completely open-loop control when MT was less than between 200 and 240 ms with corrective sub-movements increasingly frequent for movements of longer duration.

Systematic variation in performance of an interceptive action with changes in the temporal constraints

People are highly skilled at intercepting moving objects and are capable of remarkably accurate timing. The timing accuracy required depends upon the period of time for which contact with a moving target is possible--the "time window" for successful interception. Studies of performance in an experimental interception task that allows this time window to be manipulated suggest that people change aspects of their performance (movement time, MT, and movement speed) in response to changes in the time window. However, this research did not establish whether the observed changes in performance were the results of a response to the time window per se or of independent responses to the quantities defining the time window (the size and speed of a moving target). Experiment 1 was designed to resolve this issue. The speed and size of the target were both varied, resulting in variations in the time window; MT was the primary dependent measure. Predictions of the hypothesis that people respond directly to changes in the time window were verified. Predictions of the alternative hypothesis that responses to changes in target speed and size are independent of one another were not supported. Experiment 2 examined how the type of performance change observed in Experiment 1 was affected by changing the time available for executing the interception. The time available and the target speed were varied, and MT was again the primary dependent measure. MT was smaller when there was less time available, and the effect of target speed (and hence the time window) on MT was also smaller, becoming undetectable at the shortest available time (0.4 s). The results of the two experiments are interpreted as providing information about the "rule" used to preprogramme movement parameters in anticipatory interceptive actions.

Motorcycle Accident Risk Could Be Inflated by a Time to Arrival Illusion

PURPOSE

Drivers adopt smaller safety margins when pulling out in front of motorcycles compared with cars. This could partly account for why the most common motorcycle/car accident involves a car violating a motorcyclist's right of way. One possible explanation is the size-arrival effect in which smaller objects are perceived to arrive later than larger objects. That is, drivers may estimate the time to arrival of motorcycles to be later than cars because motorcycles are smaller.

METHODS

We investigated arrival time judgments using a temporal occlusion paradigm. Drivers recruited from the student population (n = 28 and n = 33) saw video footage of oncoming vehicles and had to press a response button when they judged that vehicles would reach them.

RESULTS

In experiment 1, the time to arrival of motorcycles was estimated to be significantly later than larger vehicles (a car and a van) for different approach speeds and viewing times. In experiment 2, we investigated an alternative explanation to the size-arrival effect: that the smaller size of motorcycles places them below the threshold needed for observers to make an accurate time to arrival judgment using tau. We found that the motorcycle/car difference in arrival time estimates was maintained for very short occlusion durations when tau could be estimated for both motorcycles and cars.

CONCLUSIONS

Results are consistent with the size-arrival effect and are inconsistent with the tau threshold explanation. Drivers estimate motorcycles will reach them later than cars across a range of conditions. This could have safety implications.

Hitting moving targets: effects of target speed and dimensions on movement time

To hit moving targets, one not only has to arrive at the right place but also at the right time. Moving quickly reduces spatial precision but increases temporal precision. This may explain why people usually move more quickly toward fast targets than toward slow ones, because arriving at the right time is more important when hitting fast targets. The temporal accuracy required depends not only on the target's speed but also on its length in the direction of motion; it decreases with increasing length. Here we investigate the effects of variations in the target's speed and dimensions on the subject's movement time. We asked subjects to hit targets that moved from left to right as quickly as possible with their index finger. The targets varied in length in the direction of motion (width: affecting both spatial and temporal demands), in length in the orthogonal direction (height: affecting spatial demand), and in speed (affecting temporal demand). Targets were presented in random order during one session and in blocks of trials with identical targets during another session. In the latter session subjects could optimize their strategy for each target separately. In the random condition subjects hit fast targets more quickly than slow ones. Their movement time was also affected by the target's size (the spatial demand), but not by the direction of the elongation. For the blocked condition, subjects did consider the direction of the elongation. We conclude that people do not consider an object's orientation to estimate the temporal demands of an interception task, but that they use the object's size and speed, and their experience from previous trials.

Control of striking velocity by table tennis players

This study investigated how 7 skilled table tennis players controlled velocity of a forehand drive stroke when the ball's trajectory, velocity, and spin were modified. They hit a target in response to balls launched under four different conditions. The relative and absolute times used in the backswing phase showed no significant differences among conditions. When subjects hit fastballs, there was a significant change in the time required for them to reach the peak of velocity in the forward swing phase. In addition, players decreased the velocity of their strokes to hit fast-approaching balls. These results indicate that highly skilled table tennis players need to adjust the striking velocity and striking time (relative and absolute) required to reach the peak of velocity in the forward swing phase for these task modifications. Since they used slower movement velocities to hit faster-approaching balls, skilled table tennis players may override this speed-coupling process.

Hitting a moving target: Perception and action in the timing of rapid interceptions

Different interceptive tasks and modes of interception (hitting or capturing) do not necessarily involve similar control processes. Control based on preprogramming of movement parameters is possible for actions with brief movement times but is now widely rejected; continuous perceptuomotor control models are preferred for all types of interception. The rejection of preprogrammed control and acceptance of continuous control is evaluated for the timing of rapidly executed, manual hitting actions. It is shown that a preprogrammed control model is capable of providing a convincing account of observed behavior patterns that avoids many of the arguments that have been raised against it. Prominent continuous perceptual control models are analyzed within a common framework and are shown to be interpretable as feedback control strategies. Although these models can explain observations of on-line adjustments to movement, they offer only post hoc explanations for observed behavior patterns in hitting tasks and are not directly supported by data. It is proposed that rapid manual hitting tasks make up a class of interceptions for which a preprogrammed strategy is adopted--a strategy that minimizes the role of visual feedback. Such a strategy is effective when the task demands a high degree of temporal accuracy.

Timing of goal-directed hitting: impact requirements change the information-movement coupling

In hitting, performers are found to adapt to the approach speed of the ball, i.e. they tend to initiate their movement at a shorter time before contact for faster approaching balls. A change in movement time is always accompanied by a change in movement velocity when the movement trajectory is kept constant. Hence, a fast-approaching ball might induce high impact velocity that is in conflict with low impact constraints, such as propelling the ball towards a near goal. In this study we investigated the capacities of participants to perform one-dimensional hitting movements in the frontal plane to balls approaching on a head-on collision course. The temporal precision (i.e. ball approach speed: 1, 1.5, and 2 m/s) and impact requirements (i.e. No-Goal, Near-Goal, and Far-Goal) were manipulated to examine the influence of task constraints on the temporal regulation of a stroke. The results showed that timing and speed were significantly affected by ball approach speed when the hit was not directed to a goal. In contrast, no speed-coupling and a constant time-to-impact strategy were found when impact velocity was constrained (i.e. aiming for a near goal). We were particularly interested in the nature and relation of information sources and timing patterns of movement initiation. Therefore, the relation between the time evolution of three optical sources related to the approach of the ball and the observed patterns of swing onset were evaluated quantitatively. The analyses revealed that a viable explanation for the two observed qualitatively different onset patterns of the swing is a regulation based on the absolute rate of expansion or a co-varying variable. The flexible adaptation of timing to impact constraints may be realized by an adjustment of the critical region of this optical variable.