Bending it like Beckham: how to visually fool the goalkeeper

Emergent Coordination of Heading in Soccer: Of Two Players and a Single Ball

Purpose: In many sports situations, two or more players need to coordinate their actions to make sure that one of them intercepts a ball or opponent. We considered how two soccer players head back a thrown ball. Two accounts for the joint decision making by both players were considered. These two accounts not only differ in their theoretical basis but also have vastly different implications for training practice. In a first account, players know their areas of responsibility for interception, and combine this with their prediction of the ball's landing location. In a second account, the coordination emerges from the unfolding dynamics of the system of informationally connected players and ball. According to this second account, especially for balls aimed in between the two players, both of the players may start moving and one player sees that the ball will be interceptable for the other player, and subsequently yields the interception. Methods: We instrumented soccer players and the ball with Kinexon sensors and had pairs of players head back the thrown ball. Results: In line with the second account, the results showed a fair number of instances where the player who intercepted the ball had to move the longest distance. Furthermore, considerable movement by both players was not an exception. Conclusion: The results can be taken as a first step towards an understanding of joint coordination as an emergent phenomenon.

Goalkeepers' plasticity during learning of a whole-body visuomotor rotation in a stable or variable environment

Postural adjustments performed in anticipation of uncertain visual events is a common sensorimotor control problem in open sport skills. In this study, we examined how expert soccer goalkeepers and non-athletes learn a whole body visuomotor rotation during postural tracking of constant and variable visual target motions. Twenty-one (21) soccer goalkeepers (18 ± 15 years, 75 ± 12 kg) and 25 age-matched non-athletes (18 ± 12 years, 75 ± 15 kg) practiced lateral weight shifting on a dual force platform while tracking the motion of a constant (11 goalkeepers and 12 non-athletes) or a variable (10 goalkeepers and 13 non-athletes) visual target with provision of online visual feedback (VF). After 40s of tracking (baseline), the visual presentation of the VF signal reversed direction relative to the participant's motion (180° visuo-motor rotation) for 60s (adaptation) and then returned to its veridical direction for another 20s (washout). During adaptation, goalkeepers reduced the spatiotemporal error to baseline levels at an earlier time block (3rd block) compared to non-athletes (6th block), but this difference was significant only for groups tracking of the constant and not the variable target motion. Only the groups tracking the constant target increased the spatiotemporal error during the 1st washout block demonstrating a significant aftereffect. It is concluded that goalkeepers adapt faster to the feedback rotation due to their prior field knowledge of relevant visuomotor transformations in anticipation of deceptive visual cues. This expertise advantage however is present only in a stable visual environment possibly because learning is compromised when tracking uncertain motion cues requiring closed loop control.HighlightsWe examined how expert goalkeepers and non-athletes adopt to a novel whole body visuomotor rotation when tracking a constantly or variably moving targetGoalkeepers adopted faster to the visuomotor rotation than non-athletesExpertise related differences were evident only for groups tracking the constant target motionGroups tracking the variable target motion did not learn the visuomotor rotation.

Virtual training, real effects: a narrative review on sports performance enhancement through interventions in virtual reality

The present article reports a narrative review of intervention (i.e., training) studies using Virtual Reality (VR) in sports contexts. It provides a qualitative overview and narrative summary of such studies to clarify the potential benefits of VR technology for sports performance enhancement, to extract the main characteristics of the existing studies, and to inform and guide future research. Our literature search and review eventually resulted in 12 intervention studies with a pre vs. post design focused on different sports, including target and precision sports (archery, bowling, curling, darts, golf), bat/racquet and ball sports (baseball, table tennis), goal sports (football/soccer, basketball), martial arts (karate), and sport-unspecific processes such as bodily sensations and balancing. The samples investigated in the primary studies included novice, amateur, and expert athletes (total aggregated sample size N = 493). Many studies found statistically significant effects in relevant target skills following interventions in VR, often outperforming training effects in passive or active control conditions (e.g., using conventional training protocols). Therefore, interventions in VR (or extended reality) have the potential to elicit real effects in sports performance enhancement through training of motor and psychological skills and capabilities in athletes, including perception-action skills, strategic, tactical and decision-making, responding to unexpected events, and enhancing psychological resilience and mental performance under pressure. The neurocognitive mechanisms (e.g., visual search behavior, imagery), methodological aspects (e.g., adaptive training difficulty), and the issues of real-world transfer and generalizability via which these potential sports-performance-related improvements may occur are discussed. Finally, limitations of the present review, the included studies, the current state of the field in general as well as an outlook and future perspectives for research designs and directions are taken into consideration.

From Natural Towards Representative Decision Making in Sports: A Framework for Decision Making in Virtual and Augmented Environments

Decision making is vital in complex sporting tasks but is difficult to test and train. New technologies such as virtual and augmented reality offer novel opportunities for improving decision making, yet it remains unclear whether training gains using these new approaches will improve decision making on-field. To clarify the potential benefits, a clear conceptualization of decision making is required, particularly for invasive team sports such as football, basketball and field hockey, where decisions are complex with many possible options offered. Therefore, the aim of this position paper is to establish a framework for the design of virtual and augmented environments that help invasive team sport athletes to train their decision-making capacities. To achieve this, we propose a framework for conceptualising 'natural' decision making within the performance environment in invasive team sports that views decision making as a continuous cyclical process where the ball carrier interacts with teammates to create 'windows of opportunity', and where skilled decision makers often delay decisions to create time, and in turn new opportunities, rather than necessarily selecting the first option available to them. Within the framework, we make a distinction between decision making and anticipation, proposing that decision making requires a series of on-going anticipatory judgments. Based on the framework, we subsequently highlight the consequences for testing and training decision making using virtual and augmented reality environments, in particular outlining the technological challenges that need to be overcome for natural decision making to be represented within virtual and augmented environments.

A Narrative Review of the Current State of Extended Reality Technology and How it can be Utilised in Sport

Extended reality is an umbrella term used to describe three computer-generated technologies including virtual reality, augmented reality and mixed reality. Extended reality is an emerging technology that has been utilised in many high-performance domains including psychology, medicine and the military, with the aim of enhancing perceptual-cognitive skills and motor skills. However, the use of extended reality in sport, particularly at the elite level, has only recently started to receive attention. While the growth of extended reality technology continues to accelerate at a rapid rate, empirical evidence aimed at understanding how these devices can best be applied in high-performance sport has not followed suit. Therefore, the purpose of this review is to provide clarity for high-performance sport organisations, researchers, sport scientists, coaches and athletes about the current state of extended reality technology and how it has been utilised in sport. In doing so, we first define and give examples of the types of extended reality technology including virtual reality, augmented reality and mixed reality that are available at the present time. Second, we detail how skill acquisition principles underpinned by the theoretical framework of ecological dynamics can be used to help inform the design and assessment of extended reality training tools. Third, we describe how extended reality has been utilised in sport, including how extended reality tools have been assessed for their level of representativeness, and the effectiveness of extended reality training interventions for improving perceptual-cognitive skills and motor skills. Finally, we discuss the future utilisation of extended reality in sport, including the key learnings that can be drawn from other domains, future research directions, practical applications and areas for consideration related to the use of extended reality for training skills in sport.

Virtual stick balancing: skill development in Newtonian and Aristotelian dynamics

Human reaction delay significantly limits manual control of unstable systems. It is more difficult to balance a short stick on a fingertip than a long one, because a shorter stick falls faster and therefore requires faster reactions. In this study, a virtual stick balancing environment was developed where the reaction delay can be artificially modulated and the law of motion can be changed between second-order (Newtonian) and first-order (Aristotelian) dynamics. Twenty-four subjects were separated into two groups and asked to perform virtual stick balancing programmed according to either Newtonian or Aristotelian dynamics. The shortest stick length (critical length, L_c) was determined for different added delays in six sessions of balancing trials performed on different days. The observed relation between L_c and the overall reaction delay τ reflected the feature of the underlying mathematical models: (i) for the Newtonian dynamics L_c is proportional to τ²; (ii) for the Aristotelian dynamics L_c is proportional to τ. Deviation of the measured L_c(τ) function from the theoretical one was larger for the Newtonian dynamics for all sessions, which suggests that, at least in virtually controlled tasks, it is more difficult to adopt second-order dynamics than first-order dynamics.

Visual guidance of locomotor interception is based on nulling changes in target bearing (not egocentric target direction nor target-heading angle)

In two experiments we studied how participants steer to intercept uniformly moving targets in a virtual driving task under hypotheses-differentiating conditions of initial target eccentricity and target motion. In line with our re-analysis of findings from earlier studies, in both experiments the observed interception behavior could not be understood as resulting from reliance on (changes in) egocentric target direction nor from reliance on (changes in) target-heading angle. The overall pattern of results observed was however compatible with a control strategy based on nulling changes in the target's bearing angle. The presence of reversals in movement direction under specific combinations of target eccentricity and motion conditions indicated that the information used was not purely rate-of-change (i.e., first-order) based but carried traces of an influence of initial target position. In Experiment 2 we explicitly tested the potential role of early reliance on perceived egocentric target direction by examining the effects of a 10° rotation of the visual scene (i.e., of both target and environment). While such a rotation gave rise to minor changes in the moment of initiation of the first steering action, contrary to predictions it did not affect the characteristics of the direction-reversal phenomenon. We conclude that the visual guidance of locomotor interception is best understood as resulting from nulling changes in the target's bearing angle, with such nulling perhaps best conceived as being fractional-order (rather integer-order) driven.

Assessing Visual Exploratory Activity of Athletes in Virtual Reality Using Head Motion Characteristics

Maximizing performance success in sports is about continuous learning and adaptation processes. Aside from physiological, technical and emotional performance factors, previous research focused on perceptual skills, revealing their importance for decision-making. This includes deriving relevant environmental information as a result of eye, head and body movement interaction. However, to evaluate visual exploratory activity (VEA), generally utilized laboratory settings have restrictions that disregard the representativeness of assessment environments and/or decouple coherent cognitive and motor tasks. In vivo studies, however, are costly and hard to reproduce. Furthermore, the application of elaborate methods like eye tracking are cumbersome to implement and necessitate expert knowledge to interpret results correctly. In this paper, we introduce a virtual reality-based reproducible assessment method allowing the evaluation of VEA. To give insights into perceptual-cognitive processes, an easily interpretable head movement-based metric, quantifying VEA of athletes, is investigated. Our results align with comparable in vivo experiments and consequently extend them by showing the validity of the implemented approach as well as the use of virtual reality to determine characteristics among different skill levels. The findings imply that the developed method could provide accurate assessments while improving the control, validity and interpretability, which in turn informs future research and developments.

Reversals in Movement Direction in Locomotor Interception of Uniformly Moving Targets

Here we studied how participants steer to intercept uniformly moving targets in a virtual driving task. We tested the hypothesis that locomotor interception behavior cannot fully be explained by a strategy of nulling rate of change in pertinent agent-target relations such as the target-heading angle or target’s bearing angle. In line with a previously reported observation and model simulations, we found that, under specific combinations of initial target eccentricity and target motion direction, locomotor paths revealed reversals in movement direction. This phenomenon is not compatible with unique reliance on first-order (i.e., rate-of-change based) information in the case of uniformly moving targets. We also found that, as expected, such reversals in movement direction were not observed consistently over all trials of the same experimental condition: their presence depended on the timing of the first steering action effected by the participant, with only early steering actions leading to reversals in movement direction. These particular characteristics of the direction-reversal phenomenon demonstrated here for a locomotor interception-by-steering task correspond to those reported for lateral manual interception. Together, these findings suggest that control strategies operating in manual and locomotor interception may at least share certain characteristics.

A goalkeeper's performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball

Free kicks are an important goal scoring opportunity in football. It is an unwritten rule that the goalkeeper places a wall of defending players with the aim of making scoring harder for the attacking team. However, the defensive wall can occlude the movements of the kicker, as well as the initial part of the ball trajectory. Research on one-handed catching suggests that a ball coming into view later will likely delay movement initiation and possibly affect performance. Here, we used virtual reality to investigate the effect of the visual occlusion of the initial ball trajectory by the wall on the performance of naïve participants and skilled goalkeepers. We showed that movements were initiated significantly later when the wall was present, but not by the same amount as the duration of occlusion (~200ms, versus a movement delay of ~70-90ms); movements were thus initiated sooner after the ball came into view, based on less accumulated information. For both naïve participants and skilled goalkeepers this delayed initiation significantly affected performance (i.e., 3.6cm and 1.5cm larger spatial hand error, respectively, not differing significantly between the groups). These performance reductions were significantly larger for shorter flight times, reaching increased spatial errors of 4.5cm and 2.8cm for both groups, respectively. Further analyses showed that the wall-induced performance reduction did not differ significantly between free kicks with and without sideward curve. The wall influenced early movement biases, but only for free kicks with curve in the same direction as the required movement; these biases were away from the final ball position, thus hampering performance. Our results cannot suggest an all-out removal of the wall–this study only considered one potential downside–but should motivate goalkeepers to continuously evaluate whether placing a wall is their best option. This seems most pertinent when facing expert free kick takers for whom the wall does not act as a block (i.e., whose kicks consistently scale the wall).

Virtual reality to assess and train team ball sports performance: A scoping review

Virtual reality (VR) is a widespread technology drawing an increasing interest for players and coaches, especially in team ball sports as it offers a simple tool to simulate, analyse and train situations that are often too complex to reproduce in the field. In this review we aimed at (1) providing an overview of methodologies and outcomes of research studies using VR in team ball sports; (2) better evaluating the potential interest of VR to analyse or train team ball sports situation and (3) identifying limitations, gaps in knowledge and remaining scientific challenges. The MEDLINE and Web of Science Core Collection databases were searched, using predefined combinations of keywords. Thirty articles were retained and analysed. VR can be an interesting tool to assess or train team ball sports skills/situations as it allows researchers to control and standardise situations and focus on specific skills/subskills. Studies that used VR in team ball sports still have some limitations, mainly due to technical issues or study design. This paper also describes the way VR should be used to enhance understanding of performance in team ball sports. Additional suggestions for future research and study design are proposed.

Application of Virtual Reality in Competitive Athletes - A Review

The purpose of this study was to determine the state of the art in the area of virtual reality in competitive athletes of different levels of expertise in various disciplines and point the areas of its application. Articles published before August 2018 were considered in our review. The PubMed, SCOPUS, SportDiscus and Medline databases were searched. A combination of the following search terms was used: virtual reality, virtual environment, virtual system, athletes, sports, physical training, sport performance, physical exercises. Studies involved healthy competitive athletes. A total of 18 articles met the inclusion criteria. There were three areas of application of virtual reality to sport: performance analysis, simulation improvement and virtual training. Competitive athletes were mostly examined in a semi-immersive setting. In conclusion, virtual reality seems to play a marginal role in competitive athletes' training. Due to the fact that virtual reality interventions bring significant improvements in clinical research, well-designed randomized control trials with detailed virtual training programmes are required in the future. Practically, virtual reality is effectively and commonly used to analyse performance in competitive athletes. There is still a need of creating fully interactive VR, where athletes will be able to cooperate with a virtual partner and influence the environment.

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.

Control at stability's edge minimizes energetic costs: expert stick balancing

Stick balancing on the fingertip is a complex voluntary motor task that requires the stabilization of an unstable system. For seated expert stick balancers, the time delay is 0.23 s, the shortest stick that can be balanced for 240 s is 0.32 m and there is a [Formula: see text]° dead zone for the estimation of the vertical displacement angle in the saggital plane. These observations motivate a switching-type, pendulum-cart model for balance control which uses an internal model to compensate for the time delay by predicting the sensory consequences of the stick's movements. Numerical simulations using the semi-discretization method suggest that the feedback gains are tuned near the edge of stability. For these choices of the feedback gains, the cost function which takes into account the position of the fingertip and the corrective forces is minimized. Thus, expert stick balancers optimize control with a combination of quick manoeuvrability and minimum energy expenditures.

The influence of ball-swing on the timing and coordination of a natural interceptive task

Successful interception relies on the use of perceptual information to accurately guide an efficient movement strategy that allows performers to be placed at the right place at the right time. Although previous studies have highlighted the differences in the timing and coordination of movement that underpin interceptive expertise, very little is known about how these movement patterns are adapted when intercepting targets that follow a curvilinear flight-path. The aim of this study was to examine how curvilinear ball-trajectories influence movement patterns when intercepting a fast-moving target. Movement timing and coordination was examined when four groups of cricket batters, who differed in their skill level and/or age, hit targets that followed straight or curvilinear flight-paths. The results revealed that when compared to hitting straight trials, (i) mixing straight with curvilinear trials altered movement coordination and when the ball was hit, (ii) curvilinear trajectories reduced interceptive performance and significantly delayed the timing of all kinematic moments, but there were (iii) larger decrease in performance when the ball swung away from (rather than in towards) the performer. Movement coordination differed between skill but not age groups, suggesting that skill-appropriate movement patterns that are apparent in adults may have fully emerged by late adolescence.

Comparison of the Kinematic Patterns of Kick Between Brazilian and Japanese Young Soccer Players

Background

Kicking performance is the most studied technical action in soccer and lower limbs kinematics is closely related to success in kicking, mainly because they are essential in imparting high velocity to the ball. Previous studies demonstrated that soccer leagues in different countries exhibit different physical demands and technical requirements during the matches. However, evidencewhether nationality has any influence in the kinematics of soccer-related skills has not yet been reported. The nationality of the players is an aspect that might be also relevant to the performance in kicking.

Objectives

The aim of this study was to compare the lower limbs kinematic patterns during kicking, between Brazilian and Japanese young top soccer players.

Patients and Methods

Seven Brazilian (GA) and seven Japanese (GB) U-17 players performed 15 side-foot kicks each, with a distance of 20 m away from the goal, aiming a target of 1 × 1 m in upper corner, constrained by a defensive wall (1.8 × 2 m). Four digital video cameras (120 Hz) recorded the performance for further 3D reconstruction of thigh, shank and foot segments of both kicking and support limbs. The selected kicking cycle was characterized by the toe-off of the kicking limb to the end of the kicking foot when it came in contact with the ball. Stereographical projection of each segment was applied to obtain the representative curves of kicking as function of time for each participant in each trial. Cluster analysis was performed to identify the mean GA and GB curves for each segment. Silhouette coefficient (SC) was calculated, in order to determine the degree of separation between the two groups’ curves.

Results

Comparison between the median confidence intervals of the SC showed no differences between groups as regards lower limb patterns of movements. Task accuracy was determined by the relative frequency that the ball reached the target for all attempts and no differences were found (GA: 10.48 ± 14.33%; GB: 9.52 ± 6.51%; P = 0.88).

Conclusions

We conclude that lower limb kinematic patterns, in support and ball contact phases, are similar in young Brazilian and Japanese soccer players during free kicks when adopting the side-foot kick style.

Perception of spin and the interception of curved football trajectories

Using plain white and chequered footballs, we evaluated observers' sensitivity to rotation direction and the effects of ball texture on interceptive behaviour. Experiment 1 demonstrated that the maximal distance at which observers (n = 8) could perceive the direction of ball rotation decreased when rotation frequency increased from 5 to 11 Hz. Detection threshold distances were nevertheless always larger for the chequered (decreasing from 47 to 28 m) than for the white (decreasing from 15 to 11 m) ball. In Experiment 2, participants (n = 7) moved laterally along a goal line to intercept the two balls launched with or without ±4.3 Hz sidespin from a 30-m distance. The chequered ball gave rise to shorter movement initiation times when trajectories curved outward (±6 m arrival positions) or did not curve (±2 m arrival positions). Inward curving trajectories, arriving at the same ±2 m distances from the participants as the non-curving trajectories, evoked initial movements in the wrong direction for both ball types, but the amplitude and duration of these reversal movements were attenuated for the chequered ball. We conclude that the early detection of rotation permitted by the chequered ball allowed modulation of interception behaviour without changing its qualitative characteristics.

Different temporal bases for body and arm movements in volleyball serve reception

In many sports, successfully intercepting a ball requires players to move both their body and their arms. Yet, studies of interception typically focus on one or the other. We performed an analysis of the moments of first foot and arm movements of elite-level volleyball players during serve reception. Video footage of five international matches of the Netherlands men's national volleyball team allowed the systematic coding and analysis of 347 different serve reception events. For each event, we identified the time of serve (TS) and time of contact (TC). Ball flight time (from TS to TC) varied between and within types of serve (power jump serves, n = 193, and jumping float serves, n = 154). Correlation analyses revealed that foot movement was initiated with respect to time from TS, while arm movement was initiated with respect to time until TC. These results suggest that whole-body and arm movements rely on different control processes.

Neural extrapolation of motion for a ball rolling down an inclined plane

It is known that humans tend to misjudge the kinematics of a target rolling down an inclined plane. Because visuomotor responses are often more accurate and less prone to perceptual illusions than cognitive judgments, we asked the question of how rolling motion is extrapolated for manual interception or drawing tasks. In three experiments a ball rolled down an incline with kinematics that differed as a function of the starting position (4 different positions) and slope (30°, 45° or 60°). In Experiment 1, participants had to punch the ball as it fell off the incline. In Experiment 2, the ball rolled down the incline but was stopped at the end; participants were asked to imagine that the ball kept moving and to punch it. In Experiment 3, the ball rolled down the incline and was stopped at the end; participants were asked to draw with the hand in air the trajectory that would be described by the ball if it kept moving. We found that performance was most accurate when motion of the ball was visible until interception and haptic feedback of hand-ball contact was available (Experiment 1). However, even when participants punched an imaginary moving ball (Experiment 2) or drew in air the imaginary trajectory (Experiment 3), they were able to extrapolate to some extent global aspects of the target motion, including its path, speed and arrival time. We argue that the path and kinematics of a ball rolling down an incline can be extrapolated surprisingly well by the brain using both visual information and internal models of target motion.

Neural underpinnings of superior action prediction abilities in soccer players

The ability to form anticipatory representations of ongoing actions is crucial for effective interactions in dynamic environments. In sports, elite athletes exhibit greater ability than novices in predicting other players' actions, mainly based on reading their body kinematics. This superior perceptual ability has been associated with a modulation of visual and motor areas by visual and motor expertise. Here, we investigated the causative role of visual and motor action representations in experts' ability to predict the outcome of soccer actions. We asked expert soccer players (outfield players and goalkeepers) and novices to predict the direction of the ball after perceiving the initial phases of penalty kicks that contained or not incongruent body kinematics. During the task, we applied repetitive transcranial magnetic stimulation (rTMS) over the superior temporal sulcus (STS) and the dorsal premotor cortex (PMd). Results showed that STS-rTMS disrupted performance in both experts and novices, especially in those with greater visual expertise (i.e. goalkeepers). Conversely, PMd-rTMS impaired performance only in expert players (i.e. outfield players and goalkeepers), who exhibit strong motor expertise into facing domain-specific actions in soccer games. These results provide causative evidence of the complimentary functional role of visual and motor action representations in experts' action prediction.

Prospective control in catching: the persistent Angle-of-approach effect in lateral interception

In lateral interception tasks balls converging onto the same interception location via different trajectories give rise to systematic differences in the kinematics of hand movement. While it is generally accepted that this angle-of-approach effect reflects the prospective (on-line) control of movement, controversy exists with respect to the information used to guide the hand to the future interception location. Based on the pattern of errors observed in a task requiring visual extrapolation of line segments to their intersection with a second line, angle-of-approach effects in lateral interception have been argued to result from perceptual biases in the detection of information about the ball's future passing distance along the axis of hand movement. Here we demonstrate that this account does not hold under experimental scrutiny: The angle-of-approach effect still emerged when participants intercepted balls moving along trajectories characterized by a zero perceptual bias with respect to the ball's future arrival position (Experiment 4). Designing and validating such bias-controlled trajectories were done using the line-intersection extrapolation task (Experiments 2 and 3). The experimental set-up used in the present series of experiments was first validated for the lateral interception and the line-intersection extrapolation tasks: In Experiment 1 we used rectilinear ball trajectories to replicate the angle-of-approach effect in lateral interception of virtual balls. Using line segments extracted from these rectilinear ball trajectories, in Experiment 2 we replicated the reported pattern of errors in the estimated locus of intersection with the axis of hand movement. We used these errors to develop a set of bias-free trajectories. Experiment 3 confirmed that the perceptual biases had been corrected for successfully. We discuss the implications on the information-based regulation of hand movement of our finding that the angle-of-approach effect in lateral interception cannot not explained by perceptual biases in information about the ball's future passing distance.

Metabolic rate and body size are linked with perception of temporal information

Body size and metabolic rate both fundamentally constrain how species interact with their environment, and hence ultimately affect their niche. While many mechanisms leading to these constraints have been explored, their effects on the resolution at which temporal information is perceived have been largely overlooked. The visual system acts as a gateway to the dynamic environment and the relative resolution at which organisms are able to acquire and process visual information is likely to restrict their ability to interact with events around them. As both smaller size and higher metabolic rates should facilitate rapid behavioural responses, we hypothesized that these traits would favour perception of temporal change over finer timescales. Using critical flicker fusion frequency, the lowest frequency of flashing at which a flickering light source is perceived as constant, as a measure of the maximum rate of temporal information processing in the visual system, we carried out a phylogenetic comparative analysis of a wide range of vertebrates that supported this hypothesis. Our results have implications for the evolution of signalling systems and predator–prey interactions, and, combined with the strong influence that both body mass and metabolism have on a species' ecological niche, suggest that time perception may constitute an important and overlooked dimension of niche differentiation.

•

Animals vary in their ability to perceive changes in their environment visually.

•

Temporal perception can be quantified using critical flicker fusion (CFF).

•

High CFF indicates an ability to perceive rapid changes in the visual field.

•

We show that high metabolism and small body size are associated with high CFF.

•

We argue that these findings have both ecological and evolutionary implications.

From recording discrete actions to studying continuous goal-directed behaviours in team sports

This paper highlights the importance of examining interpersonal interactions in performance analysis of team sports, predicated on the relationship between perception and action, compared to the traditional cataloguing of actions by individual performers. We discuss how ecological dynamics may provide a potential unifying theoretical and empirical framework to achieve this re-emphasis in research. With reference to data from illustrative studies on performance analysis and sport expertise, we critically evaluate some of the main assumptions and methodological approaches with regard to understanding how information influences action and decision-making during team sports performance. Current data demonstrate how the understanding of performance behaviours in team sports by sport scientists and practitioners may be enhanced with a re-emphasis in research on the dynamics of emergent ongoing interactions. Ecological dynamics provides formal and theoretically grounded descriptions of player-environment interactions with respect to key performance goals and the unfolding information of competitive performance. Developing these formal descriptions and explanations of sport performance may provide a significant contribution to the field of performance analysis, supporting design and intervention in both research and practice.

Fooling the kickers but not the goalkeepers: behavioral and neurophysiological correlates of fake action detection in soccer

Studies demonstrate that elite athletes are able to extract kinematic information of observed domain-specific actions to predict their future course. Little is known, however, on the perceptuo-motor processes and neural correlates of the athletes' ability to predict fooling actions. Combining psychophysics and transcranial magnetic stimulation, we explored the impact of motor and perceptual expertise on the ability to predict the fate of observed actual or fake soccer penalty kicks. We manipulated the congruence between the model's body kinematics and the subsequent ball trajectory and investigated the prediction performance and cortico-spinal reactivity of expert kickers, goalkeepers, and novices. Kickers and goalkeepers outperformed novices by anticipating the actual kick direction from the model's initial body movements. However, kickers were more often fooled than goalkeepers and novices in cases of incongruent actions. Congruent and incongruent actions engendered a comparable facilitation of kickers' lower limb motor representation, but their neurophysiological response was correlated with their greater susceptibility to be fooled. Moreover, when compared with actual actions, motor facilitation for incongruent actions was lower among goalkeepers and higher among novices. Thus, responding to fooling actions requires updation of simulative motor representations of others' actions and is facilitated by visual rather than by motor expertise.

Detecting deception in movement: the case of the side-step in rugby

Although coordinated patterns of body movement can be used to communicate action intention, they can also be used to deceive. Often known as deceptive movements, these unpredictable patterns of body movement can give a competitive advantage to an attacker when trying to outwit a defender. In this particular study, we immersed novice and expert rugby players in an interactive virtual rugby environment to understand how the dynamics of deceptive body movement influence a defending player’s decisions about how and when to act. When asked to judge final running direction, expert players who were found to tune into prospective tau-based information specified in the dynamics of ‘honest’ movement signals (Centre of Mass), performed significantly better than novices who tuned into the dynamics of ‘deceptive’ movement signals (upper trunk yaw and out-foot placement) (p<.001). These findings were further corroborated in a second experiment where players were able to move as if to intercept or ‘tackle’ the virtual attacker. An analysis of action responses showed that experts waited significantly longer before initiating movement (p<.001). By waiting longer and picking up more information that would inform about future running direction these experts made significantly fewer errors (p<.05). In this paper we not only present a mathematical model that describes how deception in body-based movement is detected, but we also show how perceptual expertise is manifested in action expertise. We conclude that being able to tune into the ‘honest’ information specifying true running action intention gives a strong competitive advantage.

Recognition of tennis serve performed by a digital player: comparison among polygon, shadow, and stick-figure models

The objective of this study was to assess the cognitive effect of human character models on the observer's ability to extract relevant information from computer graphics animation of tennis serve motions. Three digital human models (polygon, shadow, and stick-figure) were used to display the computationally simulated serve motions, which were perturbed at the racket-arm by modulating the speed (slower or faster) of one of the joint rotations (wrist, elbow, or shoulder). Twenty-one experienced tennis players and 21 novices made discrimination responses about the modulated joint and also specified the perceived swing speeds on a visual analogue scale. The result showed that the discrimination accuracies of the experienced players were both above and below chance level depending on the modulated joint whereas those of the novices mostly remained at chance or guessing levels. As far as the experienced players were concerned, the polygon model decreased the discrimination accuracy as compared with the stick-figure model. This suggests that the complicated pictorial information may have a distracting effect on the recognition of the observed action. On the other hand, the perceived swing speed of the perturbed motion relative to the control was lower for the stick-figure model than for the polygon model regardless of the skill level. This result suggests that the simplified visual information can bias the perception of the motion speed toward slower. It was also shown that the increasing the joint rotation speed increased the perceived swing speed, although the resulting racket velocity had little correlation with this speed sensation. Collectively, observer's recognition of the motion pattern and perception of the motion speed can be affected by the pictorial information of the human model as well as by the perturbation processing applied to the observed motion.