ISSN 0031-5125 DOI 10.2466/30.PMS.120v15x2 © Perceptual & Motor Skills 2015 Perceptual & Motor Skills: Exercise & Sport BLUE JUDOGI MAY BIAS COMPETITIVE PERFORMANCE WHEN SEEDING SYSTEM IS NOT USED: SEX, AGE, AND LEVEL OF COMPETITION EFFECTS 1, 2 URSULA F. JULIO AND BIANCA MIARKA Martial Arts and Combat Sports Research Group, School of Physical Education and Sport, University of São Paulo JOÃO P. P. ROSA AND GISCARD H. O. LIMA Center for Psychobiology and Exercise Studies, Federal University of São Paulo MONICA Y. TAKITO AND EMERSON FRANCHINI Martial Arts and Combat Sports Research Group, School of Physical Education and Sport, University of São Paulo Summary.—This study evaluated whether the judogi colour (blue or white) could influence a combat outcome (victory or defeat) in 1,233 judo official combats. Sex, age group, and level of competition were also considered in the analysis. Bino- mial probability tests showed a higher probability of an athlete's winning a combat wearing blue judogi for both sexes, levels of competition (regional and state), and for the athletes of the junior and senior categories. Thus, blue judogi may bias com- petitive outcome for both sexes in regional and state level competitions and for athletes above junior age. One basic principle of sport competition is equality, meaning that the conditions for competition should be the same for all contestants (Gutt- mann, 1978). Thus, the competitive result should be a consequence of the athlete's ability and skill to perform in a given sport and not influenced by bias of any kind. In combat sports, athletes are categorized by body mass, age, and in some disciplines by graduation achieved to increase equality among competitors (Cox, 1989; Gauthier, 2009). However, several studies have noted the existence of bias in competitive combat sports, including the influence of uniform colour (Barton & Hill, 2005; Hill & Barton, 2005; Matsumoto, Konno, Hata, & Takeuchi, 2007), home advantage (Balmer, Nevill, & Williams, 2003; Balmer, Nevill, & Lane, 2005; Julio, Panissa, Mi- arka, Takito, & Franchini, 2013), and relative age effects (Albuquerque, Ta- vares, Lage, Paula, Costa, & Malloy-Diniz, 2013). While the mechanisms or the factors affecting these bias sources are not totally understood, iden- 2015, 120, 1, 28-37. 1 Address correspondence to Ursula F. Julio, School of Physical Education and Sport, Univer- sity of São Paulo (USP), Av. Prof. Mello de Morais, 65, Butantã, São Paulo, SP—05508-030, Brazil or e-mail (ursulajulio@usp.br). 2 Financial support from CAPES—Brasil.