Academic literature on the topic 'Interceptive timing'

When intercepting a moving target, accurate timing depends, in part, upon starting to move at the right moment. It is generally believed that this is achieved by triggering motor command generation when a visually perceived quantity such as the target’s time-to-arrival reaches a specific criterion value. An experimental method that could be used to determine the moment when this visual event happens was introduced by Whiting and coworkers in the 1970s, and it involves occluding the vision of the target at different times prior to the time of movement onset (MO). This method is limited because the experimenter has no control over MO time. We suggest a method which provides the needed control by having people make interceptive movements of a specific duration. We tested the efficacy of this method in two experiments in which the accuracy of interception was examined under different occlusion conditions. In the first experiment, we examined the effect of changing the timing of an occlusion period (OP) of fixed duration (200 ms). In the second experiment, we varied the duration of the OP (180–430 ms) as well as its timing. The results demonstrated the utility of the proposed method and showed that performance deteriorated only when the participants had their vision occluded from 200 ms prior to MO. The results of Experiment 2 were able to narrow down the critical interval to trigger the interceptive action to within the period from 200 to 150 ms prior to MO, probably closer to 150 ms. In addition, the results showed that the execution of brief interceptive movements (180 ms) was not affected by the range of OPs used in the experiments. This indicates that the whole movement was prepared in advance and triggered by a visual stimulus event that occurred at about 150 ms before onset.

Interceptive timing is a fundamental ability underpinning numerous actions (e.g., ball catching), but its development and relationship with other cognitive functions remain poorly understood. Piaget suggested that children need to learn the physical rules that govern their environment before they can represent abstract concepts such as number and time. Thus, learning how objects move in space and time may underpin the development of related abstract representations (i.e., mathematics). To test this hypothesis, we captured objective measures of interceptive timing in 309 primary school children (5–11 years old), alongside scores for general motor skill and national standardized academic attainment. Bayesian estimation showed that interceptive timing (but not general motor capability) uniquely predicted mathematical ability even after we controlled for age, reading, and writing attainment. This finding demonstrates that interceptive timing is distinct from other motor skills with specificity in predicting childhood mathematical ability independently of other forms of attainment and motor capability.

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.

The question of how actions involving the interception of moving objects are perceptually timed is addressed. This question has been intimately bound up with a debate which sets the 'ecological' approach to perception and action (due to Gibson) in opposition to approaches which employ computational concepts. It is argued that modern versions of the two types of approach are not, in fact, opposed but are largely complementary and frequently equivalent. A general approach for tackling problems of peceptuo-motor control in humans and animals which integrates the two approaches is outlined. The problem of how interceptions of moving objects are perceptually controlled is investigated according to this general approach. First, the informational requirements of interceptive actions are analyzed. It is concluded that 'time-to-contact' information is critical for accurate timing. The hypothesis, due to Lee, that animals and people assume the relative velocity between target and interception point to be constant when computing time-to-contact is discussed. A scheme for the continuous control of interceptive timing based on this strategy is formulated. Having established how time-to-contact information might be used to control interceptive timing the question of the perceptual source of this informtion is examined. A mathematical analysis of the visual stimulus is provided which clarifies and extends Lee's theory concerning the visual source of time-to-contact information.

Introduction: The ideal timing to initiate orthodontic treatment is an important, yet controversial issue. The purpose of this study was to investigate the provision of orthodontic care for 7 types of skeletal dysplasia by paediatric dentists and orthodontists in Canada. Methods: A questionnaire was distributed to randomly selected orthodontists (N=140) and paediatric dentists (N=132) throughout Canada. Surveys returned within 8 weeks were included for c2 statistical analysis. Results: The response rate was 59% for orthodontists and 54% for pediatric dentists. Orthodontists and pediatric dentists differed significantly in the timing of their first orthodontic consultation (p < 0.01). More pediatric dentists used to the dental age to determine the appropriate time to initiate treatment (p < 0.01), whereas more orthodontists relied on the pubertal indicators (p < 0.01). More orthodontists would intervene in the early mixed dentition for moderate mandibular prognathia (p < 0.01); mid-mixed dentition for severe mandibular retrognathia (p < 0.01), late mixed dentition for moderate mandibular retrognathia (p < 0.01) and permanent dentition for skeletal openbite and severe mandibular prognathia (p < 0.01). Most pediatric dentists would intervene in the early and mid-mixed dentition for the specified cases of skeletal malocclusions (p < 0.05). Conclusions: The results of this investigation indicate both consistencies and variation between orthodontic and paediatric practitioners with regard to preference in treatment timing, and the factors that influence these decisions.

This thesis explored the skills underpinning expertise during an interceptive timing task through the lens of a representative learning design approach. This was achieved by: (1) examining what skilful behaviours cricket batting experts perceive to be critical to performance; (2) developing a representative skills assessment based on the batting experts perceptions and extant scientific literature; and (3) assessing the efficacy of two different practice approaches on developing the aforementioned skilful behaviours underpinning expertise. In study 1, interviews with expert cricket coaches, whom were formally highly skilled batters, revealed the multi-dimensional nature of expert performance. This encompassed the need to possess extremely proficient coordinative, cognitive, perceptual and psychological skills. Additional emergent themes included the need to be attuned to the performance environment, and the continuously evolving landscape of affordances. A temporal model of batting was created from these themes, which encompassed: (1) A general search for information about their upcoming game; (2) followed by a more specific search and attunement to the performance environment, as the batter prepares to bat; (3) culminating in the moment of ball delivery, where the batter perceives and acts based on their intentions and the trajectory of the ball; (4) concluding with their between-ball routine whereby the batter reflects on the previous delivery, relaxes by engaging in task irrelevant thoughts, and then refocuses both their intentions and attention. Given the significance of the performance environment to expert performance, study 2 examined the differences between advanced cricket batters (professional state-level) and their less-skilled counterparts, using a representative learning design framework. During this scenario, advanced batters were found to have scored more runs than both intermediate and basic skill level batters; underpinned by their ability to play more scoring shots, as well as achieve superior bat-ball contact and footwork technique ratings. The more novel findings of this experiment were that advanced batters demonstrated greater flexibility in their shot selection (i.e. vertical and horizontal bat shots), while displaying greater stability in their foot movements (predominately played shots off the front foot). Also, contrary to previous findings, the timings of key movements (i.e. front foot movement and downswing of the bat) were found to be executed later by advanced batters relative to those less-skilled. When interviewed between overs, advanced batters reported their cognitions to be more externally focused, such as describing their strategies to score runs, rather than their less-skilled counterparts, who reported more internal factors such as achieving bat-ball contact or making technical changes. Finally, advanced batters had significantly lower reported levels of nervousness prior to their performance than both intermediate and basic skill level cricket batters. These findings highlight the skill level differences between interacting actions, cognitions and emotions of cricket batters, occurring within a real-world performance environment. The final study compared the efficacy of two different practice approaches to developing those skills underpinning cricket batting expertise; specifically, the interacting actions, cognitions and emotions. Following 10-weeks of practice underpinned by a constraints-led approach (CLA) or traditional practice approach (TPA), participants in the CLA group shifted their cognitions to be more externally focused on factors such as scoring runs, while concurrently increasing the number of runs scored during the post-intervention skills-test scenario. This was a result of the CLA group executing a greater number of scoring shots, improved bat-ball contact and footwork technique ratings, compared to both their pre-intervention results and the TPA group post-intervention. The TPA group had little to no reported changes in their cognitions, while also demonstrating no significant differences in the number of runs scored, number of scoring shots, bat-ball contact or footwork technique rating from pre to post-intervention. Both groups also had a reduction in their reported nervousness levels from pre to post-intervention. Finally, the CLA group reported higher levels of enjoyment, challenge, and cognitive demand during their practice sessions compared to the TPA group. No difference was reported for the level of physical demands associated with practice, for either practice group. This experiment provides evidence for the efficacy of a CLA approach to coaching talented cricket batters. Creating practice environments that maintain appropriate perception-action couplings, and ensure intentions are in-line with performance demands, leads to the emergence of more functional movement solutions and cognitions commensurate with game play. The combined findings of this investigation extends our understanding of the skills underpinning expertise, how these skills manifest during performance across various skill levels, and how different practice approaches can impact their development. A key feature of this analysis is the consideration given to the role of the performance environment in shaping an individual’s behaviours. Representative learning design is an effective tool for researchers and practitioners investigating the manifestation of skilful behaviours, or seeking to expedite its development. Future research concerned with assessing or developing skills underpinning expertise, within environments that are characteristic of real-world settings, should consider adopting this approach.

Abstract Monitoring the geometry of hydraulically induced fractures using a variety of frac diagnostic tools is a relatively expensive but necessary step to achieve successful development of unconventional reservoirs. Valuable insights about the hydraulic fracturing process can be determined and cross-validated using an assortment of diagnostic tools. In recent years, the monitoring of pressure, temperature, and strain interactions between wells during stimulation has been providing new and detailed information about the geometry of hydraulic fractures not available before. Low Frequency Distributed Acoustic Sensing (LF-DAS) and Distributed Strain Sensing (DSS) can be used to determine the timing and location of approaching, intercepting and re-opening hydraulically induced fractures in nearby wells instrumented with Fiber Optics (FO). In the Hydraulic Fracture Test Site 2 (HFTS2) the integration of these technologies with traditional fracture geometry diagnostic tools such as Microseismic (MS) are revealing unique information about fracture geometry and the propagation tendencies of fractures generated while stimulating the Wolfcamp in the Permian Delaware Basin. In HFTS2, hydraulic fractures are sub-vertical, occurring in swarms and forming well-defined and separate Frac-Zone-Domains (FZDs). In HFTS2, both the number of microseismic events and strain interactions increase as stimulation progresses within the pad. The observed spatial and temporal dependencies in the MS and LF-DAS datasets strongly suggest there is a lot of re-opening and re-fracturing of pre-existing fractures, not only of the FZDs from the "parent/primary" wells but also from pre-existing fractures of the FZDs from offset "child/infill" wells that are part of the same stimulation vintage. These newly observed spatial and temporal effects must be considered when using MS, LF-DAS, and other fracture driven interaction (FDI) techniques to determine fracture growth velocities and when interpreting frac diagnostics results to calibrate fracture models. The data suggest that fracture growth is impacted by the location of pre-existing hydraulic fractures and their stress state. The findings in HFTS2 highlight the risk not only of misinterpreting microseismic derived Stimulated Rock Volume (SRV) but also, and more importantly the development of possible new completion practices and wells stimulation sequencing. The information from HFTS2 has helped to understand not only the fracture geometry on this Permian Wolfcamp site but also the uses and limitations of different fracture diagnostic tools.