Statistical modelling of gaze behaviour as categorical time series: what you should watch to save soccer penalties

Previous research on gaze behaviour in sport has typically reported summary fixation statistics thereby largely ignoring the temporal sequencing of gaze. In the present study on penalty kicking in soccer, our aim was to apply a Markov chain modelling method to eye movement data obtained from goalkeepers. Building on the discrete analysis of gaze employed by Dicks et al. (Atten Percept Psychophys 72(3):706–720, 2010b), we wanted to statistically model the relative probabilities of the goalkeeper’s gaze being directed to different locations throughout the penalty taker’s approach (Dicks et al. in Atten Percept Psychophys 72(3):706–720, 2010b). Examination of gaze behaviours under in situ and video-simulation task constraints reveals differences in information pickup for perception and action (Attention, Perception and Psychophysics 72(3), 706–720). The probabilities of fixating anatomical locations of the penalty taker were high under simulated movement response conditions. In contrast, when actually required to intercept kicks, the goalkeepers initially favoured watching the penalty taker’s head but then rapidly shifted focus directly to the ball for approximately the final second prior to foot-ball contact. The increased spatio-temporal demands of in situ interceptive actions over laboratory-based simulated actions lead to different visual search strategies being used. When eye movement data are modelled as time series, it is possible to discern subtle but important behavioural characteristics that are less apparent with discrete summary statistics alone.     

Examination of gaze behaviors under in situ and video simulation task constraints reveals differences in information pickup for perception and action

Queensland University of Technology, Brisbane, Queensland, Australia Gaze and movement behaviors of association football goalkeepers were compared under two video simulation conditions (i.e., verbal and joystick movement responses) and three in situ conditions (i.e., verbal, simplified body movement, and interceptive response). The results showed that the goalkeepers spent more time fixating on information from the penalty kick taker’s movements than ball location for all perceptual judgment conditions involving limited movement (i.e., verbal responses, joystick movement, and simplified body movement). In contrast, an equivalent amount of time was spent fixating on the penalty taker’s relative motions and the ball location for the in situ interception condition, which required the goalkeepers to attempt to make penalty saves. The data suggest that gaze and movement behaviors function differently, depending on the experimental task constraints selected for empirical investigations. These findings highlight the need for research on perceptual— motor behaviors to be conducted in representative experimental conditions to allow appropriate generalization of conclusions to performance environments.     

Goalkeeping in the soccer penalty kick: The dive is coordinated to the kicker's non-kicking leg placement,irrespective of time constraints

Traditionally, goalkeeping in the soccer penalty kick has been studied using video-based technology, in which goalkeepers watched video footage of penalty kicks and indicated perceived ball direction. By omitting the requirement to actually dive or jump to the ball, these studies overlooked how action capabilities constrain goalkeepers' actions. By contrast, we examined whether goalkeeping in the penalty kick is consistent with affordance-based control, that is, whether goalkeepers guide their dive by taking into account their action capabilities (i.e., the time they need to intercept the ball).To this end, high- and moderate-skilled goalkeepers faced in-situ penalty kicks. Time constraints were manipulated by varying the kicking distance and the kicker's run-up speed. The results showed that goalkeepers of both skills level scaled the lateral dive onset to their action capabilities, but high-skilled goalkeepers acted closer to their maximum action boundary. In doing so, goalkeepers did not take the varying time constraints into account. Instead, high-skilled goalkeepers acted consistent with a strategy in which they coordinated the onset of the dive with the landing of kicker's non-kicking leg next to the ball.Consequently, we only find partial support for affordance-based control. We propose that this is explained by reliable information becoming available (too) late within the spatiotemporal constraints of the penalty kick.     

Effect of verbal cueing on trajectory anticipation in the penalty kick among novice football goalkeepers

The effect of a cueing technique on novice goalkeepers' anticipation of trajectory in penalty kicks was investigated. 28 novice football goalkeepers from junior teams were randomly selected and divided into experimental (n = 14) and control (n = 14) groups. Following a pre-test, participants performed 30 trials of a simulated penalty-kicking task in a spatially occluded condition. They were required to react to penalty kicks and were informed of their performance in anticipating the direction in which the ball was kicked. The experimental group received cues about the position of the non-kicking foot of the kicker, but the control group did not. The two-way analysis of variance showed the significant main effects of blocks of trials and group, but the interaction was not significant. The experimental group more accurately anticipated the direction of the penalty kicks than the control group. The cueing technique benefited the novice goalkeepers in anticipating the direction of penalty kicks, due to the informative nature of the cue for skill execution.     

Tactical skills and ball speed during a field simulation of penalty kick strategies in soccer

This study investigates the efficacy of intermediate penalty kickers by comparing the effect of applying an automated WiFi system on the field of play to simulate a strategy that takes account of goalkeeper action (dependent) with another for which goalkeeper strategy is irrelevant (independent). Intermediate penalty kickers (n=12) took a pretreatment test of 32 kicks in a "real-play" situation with intermediate goalkeepers (n=3). Two groups of kickers underwent 11 treatment sessions using different strategies and then were administered a posttreatment test. The variables measured were the number of goals scored, whether the direction of the shot was the same or different from the direction of the goalkeeper's move (DDG), ball speed, and the duration of the kicking movement. Data suggested the goalkeepers had a greater capacity to identify advance cues when faced with independent strategy kickers and that dependent strategy kickers achieved lower ball speeds.     

Affordance-based control in deceptive and non-deceptive penalties in soccer goalkeeping: Gender matters!

Only few studies have addressed how soccer goalkeepers adapt to both the spatial and temporal constraints while trying to stop a penalty kick. Moreover, research on penalty kicks has only involved male goalkeepers, even though the resultant constraint (i.e., the relation between the maximum action capabilities defining the time required and ball flight time and direction defining the time available) may or may not differ for female goalkeepers. We therefore compared penalty goalkeeping between male and female goalkeepers of similar skill level. The results showed that the resultant constraint was more stringent for female than male goalkeepers. In accordance with the affordance-based control theory, female and male goalkeepers both adapted to the resultant constraint, but did scale their diving action differently. Female goalkeepers initiated the lateral dive within the action boundaries set by the resultant constraint, while male goalkeepers tended to dive late, beyond the action boundaries. Owing to the early dive, female goalkeepers saved more penalties than male in non-deceptive penalties. Nevertheless, female goalkeepers were also more susceptible to deception by the penalty taker than male goalkeepers. These findings extend our knowledge of the affordance-based control theory in sports and contribute to the understanding of gender differences in soccer penalty goalkeeping.     

Gaze behaviors of goaltenders under spatial-temporal constraints

It is still not known what underlies successful performance in goaltending. Some studies have reported that advanced cues from the shooter's body (hip, kicking leg or support leg) are most important (Savelsbergh, G. J. P., Williams, A. M., Van der Kamp, J., & Ward, P. (2002). Visual search, anticipation and expertise in soccer goalkeepers. Journal of Sports Sciences, 20, 279-287; Savelsbergh, G. J. P., Williams, A. M., Van der Kamp, J., & Ward, P. (2005). Anticipation and visual search behaviour in expert soccer goalkeepers. Ergonomics, 48, 1686-1697; Williams, A. M., & Burwitz, L. (1993). Advanced cue utilization in soccer. In T. Reilly, J. Clarys, & A. Stibbe (Eds.), Science and football II (pp. 239-243). London, England: E&FN Spon), while others have found that the early tracking of the object prior to and during flight is most critical (Bard, C., & Fleury, M. (1981). Considering eye movement as a predictor of attainment. In: I. M. Cockerill, & W. M. MacGillvary (Eds.), Vision and Sport (pp. 28-41). Cheltenham, England: Stanley Thornes (Publishers) Ltd.). These results are similar to those found in a number of interceptive timing studies (Land, M. F., & McLeod, P. (2000). From eye movements to actions: How batsmen hit the ball. Nature Neuroscience, 3, 1340-1345; Ripoll and Fleurance, 1988; Vickers, J. N., & Adolphe, R. M. (1997). Gaze behaviour during a ball tracking and aiming skill. International Journal of Sports Vision, 4, 18-27). The coupled gaze and motor behavior of elite goaltenders were determined while responding to wrist shots taken from 5 m and 10 m on ice. The results showed that the goalies faced shots that were significantly different in phase durations due to distance (5 versus 10 m), but this was not a factor in making saves. Instead, the ability to stop the puck was dependent on the location, onset and duration of the final fixation/tracking gaze (or quiet eye) prior to initiating the saving action. The relative onset of quiet eye was significantly (p<.001) earlier (8.6%) and the duration was longer on saves (M=80.5%; 952.3 ms) compared to goals (onset 18.86%; M=70.1%, 826.1 ms). The quiet eye was located on the puck/stick during the preparation and execution of the shot in 70.53% of all trials, or on the ice in front of the release point of the puck (25.68%) and rarely on the body of the shooter (2.1%). The results are discussed within the context of current research on goaltending with specific emphasis on the timing of critical cues and the effect of tasks constraints.     

Visual behaviors of soccer players while kicking with the inside of the foot

This study analyzed the visual behaviors of soccer players while they kicked with the inside of the foot, which involved near and far aiming skills. Participants (N = 8) were required to step forward and kick a ball to hit a target. The top three scorers were defined as the High-score group, and the three low scorers were defined as the Low-score group. Analysis indicated that the High-score group was characterized by longer quiet eye durations, which were defined as the final fixation durations on the target prior to the initiation of a kicking movement, than the Low-score group in the preparation phase. The High-score group also set their visual pivot on the frontal space between the target and the ball in the kicking phase. These two visual behaviors of the High-score group are important for soccer players to kick a ball successfully with the inside of the foot.     

“Get it out the way. The wait's killing me.” hastening and hiding during soccer penalty kicks

ObjectivesIt has been suggested that hastening and hiding—rushing through penalty preparation and not looking at the goal when preparing the penalty kick—are associated with negative penalty taking performance. In the present study, we investigated how opposing players perceived these nonverbal behaviors, how they affect outcome expectations, and how they affect the behavior of opposing goalkeepers.DesignThe present study employs an experimental research design (Experiment 1: 2 (gaze behavior) × 3 (preparation time) design; Experiment 2: 2 (gaze behavior) × 2 (preparation time) design).MethodWe examined the perception of nonverbal hastening and hiding behavior using the point-light technique during the soccer penalty kick among goalkeepers (Experiment 1a; n = 20), and among outfield soccer players (Experiment 1b; n = 29). Furthermore, we analyzed how these respective penalty preparation strategies influenced the behavior of high-level goalkeepers (n = 12) under in situ conditions (Experiment 2).ResultsThe results from Experiment 1 demonstrated that penalty takers showing hastening and hiding behaviors are perceived more negatively by both soccer goalkeepers and outfield players: (i) they are considered to possess less positive attributes, (ii) to have less accuracy in their penalties, and (iii) likely to perform less well in penalty situations. Experiment 2 provided first evidence that goalkeepers initiate their movement later following the observation of hastening and hiding behaviors during the penalty preparation.ConclusionsOur findings demonstrate the importance of investigating nonverbal behavior in sports as these have a major impact on impression formation, expected performance, and actual behavior of opposing players in the soccer penalty situation.     

The role of movement exaggeration in the anticipation of deceptive soccer penalty kicks

Human movement containing deception about the true outcome is thought to be perceived differently compared to the non‐deceptive version. Exaggeration in the movement is thought to change the perceiver's mode of functioning from an invariant to a cue‐based mode. We tested these ideas by examining anticipation in skilled and less skilled soccer players while they viewed temporally occluded (?240 ms, ?160 ms, ?80 ms, 0 ms, +80 ms) deceptive, non‐deceptive, and non‐deceptive‐exaggerated penalty kicks. Kinematic analyses were used to ascertain that the kicking actions differed across conditions. The accuracy of judging the direction of an opponent's kick as well as response confidence were recorded. Players were over confident when anticipating deceptive penalty kicks compared to non‐deceptive kicks, suggesting a cue‐based mode was used. Furthermore, there was a significant relationship between less skilled players’ confidence ratings and their accuracy 80 ms before ball‐foot contact in the deceptive and non‐deceptive‐exaggerated conditions, but not the non‐deceptive condition. Because both deceptive and non‐deceptive‐exaggerated kicks contained exaggeration, results suggest exaggerated movements in the kickers’ action at 80 ms before ball‐foot contact explains why a cue‐based mode prevails when anticipating deceptive kicks at this time point.     

Quiet-eye training for soccer penalty kicks

Anxiety has been shown to disrupt visual attention, visuomotor control and subsequent shot location in soccer penalty kicks. However, optimal visual attention has been trained in other far aiming skills, improving performance and resistance to pressure. We therefore asked a team of ten university soccer players to follow a quiet eye (QE; Vickers 1996) training program, designed to align gaze with aiming intention to optimal scoring zones, over a 7-week period. Performance and gaze parameters were compared to a placebo group (ten players) who received no instruction, but practiced the same number of penalty kicks over the same time frame. Results from a retention test indicated that the QE-trained group had more effective visual attentional control, were significantly more accurate, and had 50% fewer shots saved by the goalkeeper than the placebo group. Both groups then competed in a penalty shootout to explore the influence of anxiety on attentional control and shooting accuracy. Under the pressure of the shootout, the QE-trained group failed to maintain their accuracy advantage, despite maintaining more distal aiming fixations of longer duration. The results therefore provide only partial support for the effectiveness of brief QE training interventions for experienced performers.     

Using perceptual home-training to improve anticipation skills of soccer goalkeepers

ObjectiveThis study aims to test the effectiveness of a perceptual training concerning the anticipatory skills of soccer goalkeepers, by assessing their performances while engaged in predicting the direction of penalty kicks.DesignForty-two skilled goalkeepers were randomly assigned to three training groups: Experimental, placebo, and control. All the groups were tested at the beginning of the experiment and re-tested after a period of eight weeks.MethodThe pre-test consisted of the presentation of temporally occluded videos of penalties recorded from the goalkeeper's perspective, and participants had to predict the direction of the ball. The experimental group practiced with an interactive home-training, based on video analogous to those of the test, with the addition of both positive and negative feedback. The placebo group viewed television footage of penalty kick shoot-outs. Participants of both groups were free to schedule their own training/placebo sessions. Finally, the control group did not receive any treatment.ResultsThe results demonstrated the effectiveness of the home-training protocol, evidencing significant accuracy improvements between pre-test and post-test only for the experimental group.ConclusionsThe outcomes indicate that skilled athletes can benefit from perceptual training, which was not investigated before among soccer goalkeepers. Indeed, all the previous training studies concerning soccer penalty predictions were run on participants with either recreational or no goalkeeping experience at all. Moreover, the present training protocol is innovative because learners can schedule training sessions on their own. Finally, its usability suggests numerous potential applications.     

The power of nonverbal behavior: Penalty-takers’ body language influences impression formation and anticipation performance in goalkeepers in a simulated soccer penalty task

Previous research showed that penalty-takers’ body language affects the impressions goalkeepers form about them. Furthermore, it is often assumed that body language influences goalkeepers’ performance. However, as yet, there is no empirical evidence that indicates whether this latter effect exists. The present research was aimed at (1) replicating and offering more insight in the initial impression formation effects (Experiment 1-3) and (2) providing evidence that signals of dominance and submissiveness affect participants’ anticipation performance within a simulated soccer penalty task (Experiment 3). We report three experiments demonstrating that participants form more positive impressions and have less confidence in saving penalty kicks from dominant penalty-takers (or scoring against dominant goalkeepers, Experiment 1) than submissive penalty-takers (goalkeepers). However, we did not find evidence that participants’ automatic associations with dominant and submissive players underlie these findings (Experiment 2). Finally, we demonstrate that anticipation of kick direction is influenced by penalty-takers’ body language (Experiment 3). Participants performed worse in the simulated soccer penalty task against dominant than submissive penalty-takers. No mediation of impression formation was found.     

Individual differences in performance and learning of visual anticipation in expert field hockey goalkeepers

The study of anticipation in truly expert performers can provide insight into how they cope with extreme time constraints. The purpose of this dual-experiment paper was to investigate individual differences; in anticipation of the penalty corner drag-flick, its trainability, and transfer of improvement to field settings. Australian international and national male field-hockey goalkeepers participated. In experiment 1, international and national goalkeepers (n = 11) completed a penalty corner drag-flick temporal occlusion task that presented; defensive runner positioning at the penalty spot, drag-flicker kinematics, and ball flight. Results indicated seven goalkeepers integrated runner contextual and drag-flicker kinematic information to anticipate above chance. The cause of individual differences was independent pick-up of run and kinematic cues that presented greater opportunity to integrate sources for anticipation. In experiment 2, a sub-sample of goalkeepers participated and received temporal occlusion training or no training. Results indicated individualized improvement in anticipation across video, field, and competition assessments for those that received the intervention, but not controls. Improvements on video test were retained for six months. An individual differences approach can identify deficiencies in anticipation, which can be improved through perceptual training that transfers to motor responses. This contributes to theoretical and practical knowledge to develop anticipation skill.     

Compression and texture in socks enhance football kicking performance

The purpose of this study was to observe effects of wearing textured insoles and clinical compression socks on organisation of lower limb interceptive actions in developing athletes of different skill levels in association football. Six advanced learners and six completely novice football players (15.4 ± 0.9 years) performed 20 instep kicks with maximum velocity, in four randomly organised insoles and socks conditions, (a) Smooth Socks with Smooth Insoles (SSSI); (b) Smooth Socks with Textured Insoles (SSTI); (c) Compression Socks with Smooth Insoles (CSSI) and (d), Compression Socks with Textured Insoles (CSTI). Reflective markers were placed on key anatomical locations and the ball to facilitate three-dimensional (3D) movement recording and analysis. Data on 3D kinematic variables and initial ball velocity were analysed using one-way mixed model ANOVAs. Results revealed that wearing textured and compression materials enhanced performance in key variables, such as the maximum velocity of the instep kick and increased initial ball velocity, among advanced learners compared to the use of non-textured and compression materials. Adding texture to football boot insoles appeared to interact with compression materials to improve kicking performance, captured by these important measures. This improvement in kicking performance is likely to have occurred through enhanced somatosensory system feedback utilised for foot placement and movement organisation of the lower limbs. Data suggested that advanced learners were better at harnessing the augmented feedback information from compression and texture to regulate emerging movement patterns compared to novices.     

Gaze control in putting.

The gaze of low and higher handicap golfers was assessed while they performed consecutive putts from 3 m, wearing an eye-movement helmet that permitted normal mobility. MANOVA (count and duration), with univariate follow-up, revealed significant differences in gaze between five low (LH, 0-8) and seven higher handicap golfers (HH, 10-16). The LH (ie more highly skilled) golfers were found to use a variable form of gaze control in which longer fixation durations on the ball and target were observed, and there were fewer fixations on the club and surface, with more express saccades and quicker saccades between gaze locations. The HH golfers, in contrast, allocated the same mean durations to each gaze (about 1 s), independent of type of control (fixation, saccade, or tracking) or location (ball, club, target, or surface). In comparing hits to misses, there was an increased probability of hits if the golfers used express saccades to the club during preparation, and a steady fixation on the ball during the backswing/foreswing of the club, as well as a steady fixation on the surface during contact. These results suggest that with the acquisition of the putting skill, there are changes in gaze control, characterized by economy in the number of gaze shifts, the development of priority to specific gaze locations, and economy in the allocation of time between preferred gaze locations. In the discussion two reasons are proposed that may partially explain the results found here, as well as help further our understanding of the role of gaze in targetting skills.     

Predicting the lateral direction of deceptive and non-deceptive penalty kicks in football from the kinematics of the kicker

This study addresses the utility of the kinematics of penalty takers for goalkeepers in association football. Twelve professional and semi-professional players shot to one side of the goal with (deceptive condition) or without (non-deceptive condition) simulating a shot to the opposite side. The body kinematics of the penalty takers were registered with motion-capture apparatus. Correlation and regression techniques were used to determine the relation between the shot direction and aspects of the penalty taker’s kinematics at different moments. Several kinematic variables were strongly correlated with shot direction, especially those related to the lower part of the body. Some of these variables, including the angle of the non-kicking foot, acquired high correlations at time intervals that are useful to goalkeepers. Compound variables, here defined as linear combinations of variables, were found to be more useful than locally defined variables. Whereas some kinematic variables showed substantial differences in their relation to ball direction depending on deception, other kinematic variables were less affected by deception. Results are interpreted with the hypothesis of non-substitutability of genuine action. The study can also be interpreted as extending the correlation and regression methodology, often used to analyze variables defined at single moments, to the analysis of variables in a time continuous fashion.     

The effectiveness of penalty takers' deception: A scoping review

Attackers are supposed to take advantage of producing deceptive actions in competitive ball sports, particularly in penalty situations. We conducted a scoping review of the experimental literature to scrutinize whether penalty takers do indeed benefit from using deceptive actions in penalty situations, especially by increasing the likelihood to score a goal. Studies using video-based and in-situ tasks in which soccer and handball goalkeepers try to save a penalty were evaluated. Results showed that penalty takers' manipulation of spatial information available to the goalkeeper during deception (i.e., by using misleading and/or disguising actions) is less effective in in-situ than video-based studies. We argue that this difference occurs because goalkeepers adapt differently to the spatiotemporal constraints in the video-based and in-situ tasks. Goalkeepers appear to prioritize picking up spatial information in video-based tasks while prioritizing temporal information in-situ tasks. Therefore, the manipulation of spatial information appears to be less effective in the more representative in-situ studies than in video-based studies. In order to deceive, penalty takers are advised to manipulate temporal information during on-field penalty situations.     

Importance of head movements in gaze tracking during table tennis forehand stroke

The purpose of this study was to clarify the properties of gaze and head movements during forehand stroke in table tennis. Collegiate table tennis players (n = 12) conducted forehand strokes toward a ball launched by a skilled experimenter. A total of ten trials were conducted for the experimental task. Horizontal and vertical movements of the ball, gaze, head and eye were analyzed from the image recorded by an eye tracking device. The results showed that participants did not always keep their gaze and head position on the ball throughout the entire ball path. Our results indicate that table tennis players tend to gaze at the ball in the initial ball-tracking phase. Furthermore, there was a significant negative correlation between eye and head position especially in the vertical direction. This result suggests that horizontal VOR is suppressed more than vertical VOR in ball-tracking during table tennis forehand stroke. Finally, multiple regression analysis showed that the effect of head position to gaze position was significantly higher than that of eye position. This result indicates that gaze position during forehand stroke could be associated with head position rather than eye position. Taken together, head movements may play an important role in maintaining the ball in a constant egocentric direction in table tennis forehand stroke.     

Finding the Happy Medium: An Analysis of Gaze Behavior Strategies in a Representative Task Design of Soccer Penalties

In a field study, we conducted a soccer penalty experiment in which players had to detect the goalkeeper's movement during the run-up. We tested subjects under two conditions: the center-looking (perceiving both stimuli peripherally) and the free gaze strategy (foveal gaze on either the ball or the goalkeeper, or saccades). The center-looking strategy was superior when it came to detecting goalkeeper movements; with respect to the number of scored goals, no difference could be detected. Future research should investigate whether appropriate training in the use of the center-looking strategy might lead to a higher number of scored goals.