How the 12th Man Influences Football Matches: The Role of Fans and Referees in the Home Advantage Phenomenon.

Home advantage and referee bias are two sport factors that have been widely studied in the football (i.e., soccer) context. However, the mediating effect of spectators on these factors is not well understood, especially in the Turkish Super League. We examined (a) how variables of home advantage, referee bias, and spectator presence interacted to affect the outcome of past football matches; (b) how these variables have changed over time in the Turkish Super League; (c) and whether home advantage and referee bias differ in matches with spectators and ghost matches (without spectators). We analyzed regular season matches played in the Turkish Super League between the 2014-2015 and 2021-2022 seasons. We found that home teams had a significant advantage over away teams in matches with spectators ( < .001) and in ghost matches ( < .05 and < .001), with small to medium effect sizes ( = .09 and .34, respectively). Regarding referee bias, away teams received more yellow cards and fewer penalties than home teams in matches with spectators ( < .001; = -.10), and away teams received fewer yellow cards than home teams in ghost matches ( > .05; = .05). There was no statistically significant difference between home and away teams on number of red cards in either type of match ( > .05). Thus, our data reveal that home teams have an edge over away teams with and without spectators, but this advantage is reduced during ghost matches (without spectators). We also revealed weak evidence of referee bias in favor of home teams, but only for some variables and only when spectators were present.