Exquisite visually-guided movements underpin expertise in fast interceptive sports. The assumption that skilled performance relies on superior visual skills has been challenged by studies of sporting expertise which typically advocate vision to be a poor predictor of sporting success. This discordance is addressed in this thesis by examining whether visual degradation (in the form of blur) affects the performance of an interceptive action where successful execution demands precise spatial and temporal visual-motor control. The vision of skilled cricket batters was blurred using contact lenses (four increasing levels: plano, +1.00, +2.00, +3.00) in each of two experimental phases. In the first phase batters faced a bowling-machine and in-situ bowlers to examine the effect of blur on bat-ball interception. The highest level of blur (+3.00) was required to produce a significant decrease in batting performance when facing the bowling-machine at medium-paced ball-velocities (105-115 kph). A similar effect of blur was found when facing in-situ bowlers of comparable ball-velocity, however performance was found to be affected by a lower level of blur (+2.00) for faster-paced ball-velocities (120-130 kph). The +1.00 blur was concluded even at this higher ball-velocity to have no measurable effect on interceptive performance in a natural setting. The second phase sought to investigate the effect of blur on anticipation: a perceptual skill established to be an important component of expertise in many interceptive sports. It was established, using temporal occlusion of a bowling sequence, that optimal anticipation required an opportunity for bat-ball interception (facilitating close coupling between perception and action). Coupled anticipation demonstrated velocity-dependent resilience to blur; +3.00 and +2.00 were required for respective decreases in the anticipation of action-sequences for medium- and fast-paced ball-velocities. Remarkably, results suggest that blur may enhance uncoupled (verbal) anticipation according to the movement velocity of the bowler. Experimental results led to the conclusion that clear vision is not necessarily required for optimal interceptive performance, even when the demanding spatio-temporal task simulates the conditions experienced at the highest levels of competition. Results are interpreted based on the predictions of the dual-pathway theory of vision, including differences in the underlying visual information processed via these pathways.

Exquisite visually-guided movements underpin expertise in fast interceptive sports. The assumption that skilled performance relies on superior visual skills has been challenged by studies of sporting expertise which typically advocate vision to be a poor predictor of sporting success. This discordance is addressed in this thesis by examining whether visual degradation (in the form of blur) affects the performance of an interceptive action where successful execution demands precise spatial and temporal visual-motor control. The vision of skilled cricket batters was blurred using contact lenses (four increasing levels: plano, +1.00, +2.00, +3.00) in each of two experimental phases. In the first phase batters faced a bowling-machine and in-situ bowlers to examine the effect of blur on bat-ball interception. The highest level of blur (+3.00) was required to produce a significant decrease in batting performance when facing the bowling-machine at medium-paced ball-velocities (105-115 kph). A similar effect of blur was found when facing in-situ bowlers of comparable ball-velocity, however performance was found to be affected by a lower level of blur (+2.00) for faster-paced ball-velocities (120-130 kph). The +1.00 blur was concluded even at this higher ball-velocity to have no measurable effect on interceptive performance in a natural setting. The second phase sought to investigate the effect of blur on anticipation: a perceptual skill established to be an important component of expertise in many interceptive sports. It was established, using temporal occlusion of a bowling sequence, that optimal anticipation required an opportunity for bat-ball interception (facilitating close coupling between perception and action). Coupled anticipation demonstrated velocity-dependent resilience to blur; +3.00 and +2.00 were required for respective decreases in the anticipation of action-sequences for medium- and fast-paced ball-velocities. Remarkably, results suggest that blur may enhance uncoupled (verbal) anticipation according to the movement velocity of the bowler. Experimental results led to the conclusion that clear vision is not necessarily required for optimal interceptive performance, even when the demanding spatio-temporal task simulates the conditions experienced at the highest levels of competition. Results are interpreted based on the predictions of the dual-pathway theory of vision, including differences in the underlying visual information processed via these pathways.

A wide literature of predominantly behavioural experiments that use Stimulus Response Compatibility (SRC) have suggested that visual action information such as object affordance yields rapid and concurrent activation of visual and motor brain areas, but has rarely provided direct evidence for this proposition. This thesis examines some of the key claims from the affordance literature by applying electrophysiological measures to well established SRC procedures to determine the verities of the behavioural claims of rapid and automatic visuomotor activation evoked by viewing affording objects. The temporal sensitivity offered by the Lateralised Readiness Potential and by visual evoked potentials P1 and N1 made ideal candidates to assess the behavioural claims of rapid visuomotor activation by seen objects by examining the timecourse of neural activation elicited by viewing affording objects under various conditions. The experimental work in this thesis broadly confirms the claims of the behavioural literature however it also found a series of novel results that are not predicted by the behavioural literature due to limitations in reaction time measures. For example, while different classes of affordance have been shown to exert the same behavioural facilitation, electrophysiological measures reveal very different patterns of cortical activation for grip-type and lateralised affordances. These novel findings question the applicability of the label ‘visuomotor’ to grip-type affordance processing and suggest considerable revision to models of affordance. This thesis also offers a series of novel and surprising insights into the ability to dissociate afforded motor activity from behavioural output, into the relationship between affordance and early visual evoked potentials, and into affordance in the absence of the intention to act. Overall, this thesis provides detailed suggestions for considerable changes to current models of the neural activity underpinning object affordance.