The relative age effect in European professional soccer: did ten years of research make any difference?

The relative age effect (RAE) refers to an asymmetry in the birth-date distribution favouring players born early in the selection year and discriminating against participants born later in the year. While the RAE effect was initially reported in sport more than two decades ago, there have been few attempts to examine whether player selection strategies have changed over time in light of our improved understanding of the phenomenon. We compared the birth-date distributions of professional soccer players in ten European countries over a 10-year period involving the 2000-2001 and 2010-2011 competitive seasons, respectively. Chi-square goodness-of-fit tests were used to compare differences between the observed and expected birth-date distributions across selection years. Generally, results indicated no change in the RAE over the past 10 years in professional soccer, emphasizing the robust nature of this phenomenon. We propose a change in the structure of youth involvement in soccer to reduce the impact of the RAE on talent identification and selection.

Relative age effects in professional German soccer: a historical analysis.

Relative age effects (RAEs) refer to the specific selection, participation and attainment (dis)advantages which occur as a result of physical and cognitive differences within annual age-grouped cohorts. The present study tracked the existence of RAEs in professional German soccer by examining RAEs in players, head coaches and referees who represented professional soccer clubs or officiated in the Bundesliga from 1963/64 to 2006/07. An additional objective was to consider the social-cultural mechanisms responsible for RAEs, so for a similar period, population and soccer participation information was also obtained. When players were categorised into half decade groups, chi-square analyses predominantly showed RAEs across the history of the Bundesliga, irrespective of dates used for annual age grouping in junior/youth soccer. RAEs were also apparent for head coaches but not for referees. Participation data indicated consistent and progressive growth from 1950 to 1990. RAEs influence the likelihood of attaining professional player and coaching status in German soccer. With many coaches being former players, inequalities associated with annual age-grouping appear to extend beyond a playing career. Officiating was not affected, with referees suggested to emerge from an alternative development pathway. Increased popularity of soccer may have propagated RAEs over time, through intensification of competition and selection mechanisms.

Observational training in visual half-fields and the coding of movement sequences.

An experiment was conducted to determine if gating information to different hemispheres during observational training facilitates the development of a movement representation. Participants were randomly assigned to one of three observation groups that differed in terms of the type of visual half-field presentation during observation (right visual half-field (RVF), left visual half-field (LVF), or in central position (CE)), and a control group (CG). On Day 1, visual stimuli indicating the pattern of movement to be produced were projected on the respective hemisphere. The task participants observed was a 1300 ms spatial-temporal pattern of elbow flexions and extensions. On Day 2, participants physically performed the task in an inter-manual transfer paradigm with a retention test, and two contralateral transfer tests; a mirror transfer test which required the same pattern of muscle activation and limb joint angles and a non-mirror transfer test which reinstated the visual-spatial pattern of the sequence. The results demonstrated that participants of the CE, RVF and the LVF groups showed superior retention and transfer performance compared to participants of the CG. Participants of the CE- and LVF-groups demonstrated an advantage when the visual-spatial coordinates were reinstated compared to the motor coordinates, while participants of the RVF-group did not promote specific transfer patterns. These results will be discussed in the context of hemisphere specialization.