Affordance-based control in the soccer penalty kick
Authors:   , Zheng Ran 
Published: March 2024

This thesis explores penalty kicks in soccer from the perspective of ecological psychology, focusing on the perception of affordance during movement control. The research comprises two main themes: affordance-based control of goalkeepers and false perception of affordance in both goalkeepers and penalty takers.
In the first theme, which consists of Chapters 2 and 3, I examined whether goalkeepers controlled their dive onset in accordance with the affordance-based control theory by scaling the dive onset to their maximum action capabilities. To this end, I asked male goalkeepers in different skill levels to save penalty kicks under different spatiotemporal constraints in Chapter 2, and compared the penalty goalkeeping performance between male and female goalkeepers with similar functional skill level in Chapter 3. The results of the two chapters are consistent and partially align with the affordance-based control theory. Consistent with the theory’s predictions, I found that goalkeepers of both skill levels scaled the dive onset to their action capabilities in Chapter 2. In Chapter 3, both male and female goalkeepers adapted similarly to the resultant constraints. However, in both chapters, goalkeepers of both skill levels, as well as male and female goalkeepers, on average, waited too long before initiating their dives and acted beyond their action boundaries.
In the second theme, which encompasses Chapters 4 and 5, I examined the concept of false affordance from the perspectives of both goalkeepers and penalty takers. Chapter 4 aimed to assess the effectiveness of penalty takers’ deception by reviewing existing studies. The results showed that in the all reviewed studies, researchers required penalty takers to manipulate the spatial information to deceive goalkeepers. Penalty takers benefited more from these manipulations in video-based studies than in in-situ studies. I argued that these setting-dependent effects of spatial deception stemmed from goalkeepers’ adaptation to the distinct spatiotemporal constraints of two experimental settings. Specifically, goalkeepers were predominantly constrained to pick up spatial and temporal information in video-based and in-situ setting, respectively. Chapter 5 sought to investigate overall effectiveness of goalkeepers’ use of deception during competition, as well as the efficacy of each category classified by the type of false possibilities for action it invited. The results revealed that goalkeepers improved their performance when using deceptive actions compared to when not using them. Yet, performance improvement was comparable between the two types of deceptive actions, suggesting non-specific effects of different types of deception.
In Chapter 6, I further explored the effect of audiences on the penalty kicking performance. I compared the in-game penalty kick outcome in matches with and without the presence of audiences. The results showed that penalty takers from home teams reduced the number of missed when audiences were absent compared to when they were present, supporting the choking under pressure hypothesis. The findings in Chapters 5 and 6 suggest that stressors during competition, such as the presence of home audiences and goalkeepers’ deceptive actions, may increase the anxiety of penalty takers, thereby impairing their penalty kicking performance.
In conclusion, penalty takers have the predominant advantage during a penalty kick. It is almost impossible for goalkeepers to save the ball if penalty takers direct the ball to either top corner with adequate power. This is mainly due to the stringent spatiotemporal constraints faced by goalkeepers in reaching the ball and their limited action capabilities, rather than difficulties in diving to the correct side, as emphasized in video-based studies. Yet, goalkeepers are not entirely without chance of saving a penalty. They can enhance the maximum action capabilities during training and decrease penalty takers’ performance with deceptive actions during competition, thereby increasing their chances of saving a penalty.