Bart Gilis

Decision-making skills, role specificity, and deliberate practice in association football refereeing

Abstract In association football, two similar but arguably different refereeing roles are required, those of the referee and assistant referee. Role specificity was investigated with a foul play assessment task and an offside decision-making task. Deliberate practice was investigated to account for role-specific differences. First, role specificity was clearly observed. Second, years of officiating, hours of practice per week, and number of matches officiated were each positively correlated with skill. The results support role specificity in association football refereeing. Further research should help to create role-specific perception and decision-making training programmes both for referees and assistant referees.

Errors in judging “offside” in association football: Test of the optical error versus the perceptual flash-lag hypothesis

Abstract The objective of this study was to analyse the correctness of the offside judgements of the assistant referees during the final round of the FIFA 2002 World Cup. We also contrasted two hypotheses to explain the errors in judging offside. The optical error hypothesis is based on an incorrect viewing angle, while the flash-lag hypothesis refers to perceptual errors associated with the flash-lag effect (i.e. a moving object is perceived as spatially leading its real position at a discrete instant signalled by a briefly flashed stimulus). Across all 64 matches, 337 offsides were analysed using digital video technology. The error percentage was 26.2%. During the first 15 min match period, there were significantly more errors (38.5%) than during any other 15 min interval. As predicted by the flash-lag effect, we observed many more flag errors (86.6%) than non-flag errors (13.4%). Unlike the predictions of the optical error hypothesis, there was no significant difference between the correct and incorrect decisions in terms of the positioning of the assistant referees relative to the offside line (0.81 and 0.77 m ahead, respectively). To reduce the typical errors in judging offside, alternative ways need to be considered to teach assistant referees to better deal with flash-lag effects.

Offside Decisions by Expert Assistant Referees in Association Football: Perception and Recall of Spatial Positions in Complex Dynamic Events

This study investigated the offside decision-making process in association football. The first aim was to capture the specific offside decision-making skills in complex dynamic events. Second, we analyzed the type of errors to investigate the factors leading to incorrect decisions. Fédération Internationale de Football Association (FIFA; n = 29) and Belgian elite (n = 28) assistant referees (ARs) assessed 64 computer-based offside situations. First, an expertise effect was found. The FIFA ARs assessed the trials more accurately than the Belgian ARs (76.4% vs. 67.5%). Second, regarding the type of error, all ARs clearly tended to raise their flag in doubtful situations. This observation could be explained by a perceptual bias associated with the flash-lag effect. Specifically, attackers were perceived ahead of their actual positions, and this tendency was stronger for the Belgian than for the FIFA ARs (11.0 vs. 8.4 pixels), in particular when the difficulty of the trials increased. Further experimentation is needed to examine whether video- and computer-based decision-making training is effective in improving the decision-making skills of ARs during the game.

Activity profile of top-class association football referees in relation to performance in selected physical tests

Abstract The aims of the present study were (1) to analyse the physical demands of top-class referees and (2) to compare their official FIFA fitness test results with physical performance during a match. The work rate profiles of 11 international referees were assessed during 12 competitive matches at the 2003 FIFA Under-17 World Cup and then analysed using a bi-dimensional photogrammetric video analysis system based on direct lineal transformation (DLT) algorithms. In the first 15 min of matches, the referees were more active, performing more high-intensity exercise (P < 0.01) than in the first 15 min of the second half. During the second half of matches, the referees covered a shorter distance (P < 0.01), spent more time standing still (P < 0.05), and covered less ground cruising (P < 0.05), sprinting (P < 0.05), and moving backwards (P < 0.001) than in the first half. Also in the second 45 min, the distance of referees from infringements increased (P < 0.05) in the left attacking zone of the filed. There was also a decrease (P < 0.05) in performance in the period following the most high-intensity activity, compared with the mean for the 90 min. Time spent performing high-intensity activities during a match was not related to performance in the 12-min run (r 2 = 0.30; P < 0.05), the 200-m sprint (r 2 = 0.05; P < 0.05), or the 50-m sprint (r 2 = 0.001; P < 0.05). The results of this study show that: (1) top-class referees experienced fatigue at different stages of the match, and (2) the typical field tests used by FIFA (two 50-m and 200-m sprints, followed by a 12-min run) are not correlated with match activities.

Interpretation and application of the offside law by expert assistant referees: Perception of spatial positions in complex dynamic events on and off the field

Abstract Baldo et al. (2002) and Helsen et al. (2006) considered the flash-lag effect to explain errors made by assistant referees when judging offside in association football. The main aims of the present study were as follows: (1) to determine whether the flash-lag effect emerges in offside situations on the field of play or off the field when presented as computer animations or as video footage of real-life matches; (2) to examine offside decision-making errors in two standards of assistant referee – international FIFA and Belgian national referees. The results support the flash-lag hypothesis in several ways. First, both the FIFA and Belgian assistant referees were more likely to make errors by raising their flag when they had to assess offside situations on the field of play and when presented as three-a-side computer animations. Second, more flag errors were made when the defender moved in the opposite direction to that of the attacker. Third, the strategy of raising the flag in case of doubt was not observed when an interpretation of the offside law had to be made about the involvement of play of an attacker. Future research is needed to examine the extent to which on- and off-the-field training sessions can be used as training tools to improve offside decision-making.

Offside decision making of assistant referees in the English Premier League: Impact of physical and perceptual-cognitive factors on match performance

Abstract In the present study, we investigated the accuracy of offside judgements of assistant referees in the English Premier League. The moment in the match, the position and movement speed of the assistant referee, attacker and second-last defender, together with the angle of view for the assistant referee were all considered to underlie incorrect decisions. The error rate was 17.5% (868 of 4960 situations). As the English assistant referees tended not to signal in doubtful situations (c = 0.91), there was an overall bias towards non-flag errors (773 non-flag errors vs. 95 flag errors). The flash-lag hypothesis could explain all flag errors, whereas the optical-error hypothesis could explain a proportion of the non-flag errors (45.4%). Fatigue, movement speed, and angle of view did not have a detrimental effect on offside decision making. In conclusion, there were fewer flag errors than in the 2002 and 2006 FIFA World Cups, whereas the number of non-flag errors rose. The increased awareness of factors involved in offside decision making and the instructions to give the benefit of the doubt to attackers could have contributed to this situation.

Analysis of the kinematical demands imposed on top-class assistant referees during competitive soccer matches.

The aim of this study was to describe the kinematical demands placed on soccer assistant referees during the 2003 U-17 World Championship, and to examine the relationship between the results in the fitness tests adopted by FIFA and match activities. Twenty-two international-level assistant referees were observed during 12 matches and computerized analysis of match activities was performed using a two-dimensional photogrammetric video analysis system based on DLT (direct lineal transformation) algorithms. Before the start of the tournament, the assistant referees completed a 2 × 50-m sprint test and a 12-minute run test. Assistant referees covered on average 6137 ± 539 m during the matches, with 20% of the total distance covered at high velocities (speeds faster than 13 km·h−1). During the second half, time spent standing still increased (P < 0.01) and distance covered jogging (P < 0.05), cruising (P < 0.01) and moving sideways (P < 0.001) decreased. The score in the 12-minute run test showed a low correlation with the entire match distance (r = 0.24; P > 0.05) and with the time spent exercising at a high intensity (r = 0.35; P > 0.05). The 50-m sprint time was not significantly correlated (r = −0.38; P > 0.05) with time spent within the high-intensity activities category. The results of this study demonstrate that assistant referees experience unique kinematical demands during soccer officiating and that the score in the battery of fitness tests adopted by FIFA was not correlated to match activities.

Offside decision making in the 2002 and 2006 FIFA World Cups

Abstract The first objective of the present study was to examine the accuracy of offside judgements of assistant referees during the 2006 World Cup and to compare overall results with performances of assistant referees during the 2002 World Cup. Second, we also examined underlying mechanisms leading to incorrect decisions. According to the definition used for the 2002 World Cup, the results revealed a decrease in the number of incorrect flag signals during the 2006 (24/240 or 10.0%) compared with the 2002 World Cup (58/222 or 26.1%) (P < 0.001). For accuracy of all potential offside situations, according to a new definition (with the attacker 2 m in front or behind the second-last defender), the error percentage was 7.6% (17 flag errors and 9 non-flag errors out of 342 situations). Overall, quality of offside decisions was not influenced by the position of the assistant referee relative to the offside line. In addition, flag errors can best be explained by the perceptual illusion induced by the flash-lag effect.

Helsen, Gilis, and Weston (2006) do not err in questioning the optical error hypothesis as the only major account for explaining offside decision-making errors

Abstract Oudejans, Bakker, and Beek (2007) recognize several relevant aspects of offside judgements in association football in the paper by Helsen, Gilis, and Weston (2006). We agree that the existing knowledge base on offside assessment needs to be expanded for two reasons. First, from a theoretical point of view it is important to examine how assistant referees can learn to deal with the limitations of the human visual information processing system. Second, from a practical point of view it is relevant to understand better refereeing performances and to identify potential explanations for incorrect offside decisions that could impact on the final outcome of the game. Oudejans et al. (2007) believe we both misinterpreted the optical error hypothesis and that our data set was unsuited to test it. Below, we react to these comments.