M.Phil. (Optometry) / In football, vision is one of the key performance indicators and ingredients of success (Buys, 2002) and it is not uncommon to find a player underperforming in the field of play due to poor vision. Football is the world’s most popular sport, with the Football World Cup finals attracting record estimations of world-wide television audiences in the billions (Clark, 2007). In this sport, players must perform motor skills and control their posture during their game, while using visual information to collaborate with other team members or to oppose the opponent (Paillard & Noe’, 2006). Visual attention plays an important role in football, where players must monitor the activities and positions of multiple players simultaneously (Memmert, Simons & Grimme, 2009). As pointed out by Coopoo, Moss, Fortuin, Freese and Cameron (2012), visual capabilities and skills cannot be assumed as natural attributes but must be tested and subjected to training according to need. In this study quantitative and descriptive research is conducted to assess the visual skills of football players. Inferential statistics are done on the collected data to explain the performance of the players: A battery of twelve (12) vision related procedures were performed on each of sixty three (63) football players from two academies in Gauteng Province. The procedures are divided into ‘hardware’ and ‘software’ visual skills (Ferreira, 2002). Using the existing protocols, a comparison with existing norms is made (Buys, 2002; Buys & Ferreira, 2008). In the present study a majority of the athletes performed better in the ‘hardware’ visual skills like static visual acuity, colour discrimination, stereopsis and fusion flexibility. The athletes did not fare better in other ‘hardware’ skills like contrast sensitivity and focus flexibility. Very few of the athletes were able to score ‘above average’ and better in the ‘software’ visual skills. According to Abernethy (1986), visual performance in sport is the interaction between the ‘hardware’ and ‘software’ visual systems, and it is the ‘software’ visual system that distinguishes experts from non-experts (Ferreira, 2002; Ludeke & Ferreira, 2003; Venter & Ferreira, 2004). The ‘hardware’ of the visual system can set the potential limit to visual performance 5 in sport but once deficiencies have been addressed, it is the ‘software’ skills that will separate experts from novices (Ferreira, 2003). The ability of the sport to divide families, communities and nations along support lines tells us that there is more importance attached to the game of football than we are willing to acknowledge. Attention must therefore be paid to the performance indicators (sports vision, etc.), which have on many occasions influenced the outcomes of games. The SPSS statistical package was used to test for any statistical significance in the correlations test between player age, player position on the field of play, and player years of experience against the players’ visual skills.

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A considerable amount of research exists on the subjective perception of three-dimensional structure from texture gradients. The present set of experiments extends these tests of phenomenal perception by examining the underlying processes used in interpreting slant-from-texture. The first two experiments show that measures of subjective perception predict speeded performance in a visual search task, and that the mediating representation relies on an assumption of projective size (i.e., discriminating the size of the target is difficult when the short target is far or the long target is near). The third experiment shows that sensitivity to apparent depth in the texture display is present even in rapid and parallel search conditions where early vision is known to operate. The fourth experiment assesses the relative contribution of two dominant dimensions of the texture gradient -- "perspective" (i.e., a radial pattern) and "compression" (i.e., a foreshortened pattern). Both dimensions are detected by early vision as signals for apparent depth. The fmal experiment examines how early vision codes these two dimensions. Sternberg's (1969) Additive Factors Method (AFM) is used to assess separability of encoding, and Blalock's path analysis (1962, 1985) is used to examine the order of encoding. AFM shows that perspective and compression have independent influences on search performance in the most rapid search conditions, but that their interaction increases as search slows. The path analysis shows further that when both texture dimensions are available, perspective exerts a more immediate and perhaps even an exclusive influence on performance. These findings support the view that perspective and compression are coded separately at the earliest stages of visual processing and share a common code only later in visual processing. / Arts, Faculty of / Psychology, Department of / Graduate

This thesis claims that metacontrast unmasking is influenced by attentional orienting towards the target location. This view is contrary to Breitmeyer, Rudd and Dunn (1981), who proposed that metacontrast unmasking is the product of inhibition of the primary mask's transient signal by the sustained signal of a secondary mask. A series of experiments demonstrate the thesis using a task in which observers discriminated the missing corner of a target diamond. Experiments 1 and 2 replicated metacontrast masking and unmasking, respectively, experiment 3 illustrated that contour proximity had no influences on unmasking, contrary to dual-channel inhibition theory. Experiments 4 and 5 indicated that metacontrast unmasking was influenced by spatial orienting. We propose an addition of attention to dual-channel theory as it is incomplete with regards to metacontrast unmasking. / Arts, Faculty of / Psychology, Department of / Graduate

Twelve spatial-cueing experiments examined stimulus-driven and goal-driven control of visual attention orienting under multiple-cue conditions. Spatial cueing involves presenting a cue at a potential target location before a target appears in a display, and measuring the cue's effect on responses to the target stimulus. Under certain conditions, a cue that appears abruptly in a display (direct cue) can speed responses to a target appearing at the previously cued location relative to other uncued locations (called the cue effect). The experiments in this dissertation used a new multiple-cue procedure to decouple the effects of stimulus-driven and goal-driven processes on the control of attention. This technique involved simultaneously presenting a red direct cue (Unique Cue) that was highly predictive of the target location along with multiple grey direct cues (Standard Cues) that were not predictive of the target location. The basic finding was that while cue effects occurred at all cued locations, they were significantly larger at the Unique-Cue location. This finding was interpreted as evidence for stimulus-driven cue effects at all cued locations with additional goal-driven cue effects at the Unique-Cue location. Further experiments showed that Standard-Cue effects could occur independently at multiple locations, that they seemed to involve a sensory-based interaction between the cues and the target, and that they were mediated by a limitedcapacity tracking mechanism. In addition, Unique-Cue effects were found to be the product of goal-driven operations, to interact with Standard-Cue effects, and to involve inhibited processing at unattended locations. These results were explained in terms of a filter-based model of attention control that assigns priority to potential attention-shift destinations. According to this model, stimulus-driven and goal-driven factors generate signals (activity distributions) that drive a filter to open an attention channel at the highest priority location by suppressing the signals at other locations. The final experiments confirmed the central assumptions of this model by providing evidence that the prioritydestination process was sufficient to produce cue effects independent of attention, and that attending to a location involved a suppression of processing at unattended locations. The implications of this model for the larger visual attention literature were also discussed. / Arts, Faculty of / Psychology, Department of / Graduate

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