Precise visual-motor coordination underpins success in fast-ball sports. Previous studies highlight significant differences in both the gaze and kinematic behaviour of skilled and lesser-skilled performers when carrying out interceptive actions (e.g., predictive eye movements and temporal coupling between the body and the hitting implement). However, much of what we know is based largely on studies that adopt case-study designs and/or simplified task environments, making it difficult to generalise the findings to the wider population and to the challenging tasks actually encountered in the performance environment. This is particularly true when seeking to intercept targets that follow a curved or swinging flight-path rather than a straight trajectory. Successful interception in the presence of ball-swing requires remarkable spatio-temporal precision, and helps to test performance at the limits of human performance. Therefore, the aim of this thesis is to establish a comprehensive understanding of the development of visual-motor expertise using interception in the presence of ball-swing as a model of a highly demanding interceptive task.
The four experimental chapters in this thesis collectively report the findings of one large-scale experiment that assessed the visual-motor behaviour of cricket batters in situ. In the experiment, four groups of batters, who systematically differed according to their level of batting skill and age, attempted to hit balls projected by a hybrid ‘ProBatter’ ball-machine. Crucially, balls travelled at speeds that reflected those experienced during competition and ball-swing was introduced to manipulate task difficulty. Batters wore a portable eye tracking system to record their gaze direction, and high-speed video footage was used to analyse kinematic behaviour.
Kinematic behaviours have been shown to underpin success and distinguish batters of different skill levels when hitting a ball. However, little is known about how widely these findings generalise to actions performed in more representative task conditions (e.g., faster ball-speeds and swinging flight-paths). Therefore, the first experimental chapter (Chapter 2) aims to examine the development of timing and movement coordination when hitting a ball in these conditions. Kinematics were compared when batters intercepted balls that followed a (i) straight flight-path only, and (ii) random mixture of straight and swinging flight-paths. Results revealed skill-based differences in interceptive performance when hitting straight balls, with the performance of all batters decreasing in the presence of ball-swing (particularly when the ball swung away from the batter). Ball-swing delayed the timing of most key moments in the hitting action, with batters increasing the velocity of bat-swing to overcome those delays. Knowledge that the ball could swing (hitting straight balls mixed with swinging trajectories) also altered the batting kinematics, highlighting the potential impact of top-down cognitive influences on kinematics and performance.
Eye movement strategies also underpin skill in interception, yet almost all studies of gaze in interception have employed case-study designs that may fail to accurately capture the behaviour of the wider population. The second and third experimental chapters sought to examine the gaze behaviour of batters when intercepting balls that followed a straight trajectory (Chapter 3) and a combination of straight and swinging trajectories (Chapter 4). Results revealed strong markers of expertise (e.g., the prevalence of predictive saccades towards bat-ball contact) but also failed to support some existing measures (e.g., that better batters make earlier saccades to ball-bounce). Ball-swing reduced interceptive performance as a result of both increased uncertainty and the greater spatio-temporal precision required for interception. It revealed new markers of expertise that were not present when facing only straight trajectories and showed that batters make specific visual-motor adaptations in an attempt to account for the swinging ball (e.g., oblique predictive saccades).
Vision and motor actions work in a coordinative fashion and so the examination of gaze and kinematics in isolation may overlook critical interactions that underpin expertise in interception. The final experimental chapter (Chapter 5) examines for the first time the relationship between gaze and kinematics when intercepting a fast-moving ball. Results revealed skill-related differences in visual-motor coordination: for skilled batters the anticipatory saccades towards ball-bounce were temporally related to the batter’s kinematics (initiation of bat-downswing), but for the lesser-skilled batters saccades were related to an external event (moment of ball-bounce). Moreover, kinematic behaviour differed when predictive saccades were not performed, providing evidence that a functional interaction between gaze and kinematics helps to support successful interception.
Collectively, the results establish a clearer picture of the strategies that underpin skilled interception, with skill-based differences in gaze and kinematics found to be evident by late adolescence and sustained into adulthood when hitting straight and swinging targets. Interception in the presence of ball-swing was found to significantly influence not only batting performance but also visual-motor behaviour. The experimental series establishes a comprehensive understanding of the development of visual-motor expertise, providing a foundation for the development of talent identification and training paradigms designed to detect and improve skill in batting.