Surging testosterone could be a major explanation for the home advantage in football, say UK psychologists.
They found that all members of a squad - and goalkeepers in particular - have much higher levels of the hormone before a home game than before an away match.
"It is clear there is a big home advantage, and we think testosterone is a major factor that has been overlooked by theorists in the past," says Sandy Wolfson of the University of Northumbria, who conducted the research with colleague Nick Neave.
Home team advantage
"We know testosterone is linked to dominance and aggression in animals," says Neave. "We're trying to tie the results in with territoriality. The idea is that if you're playing at home, you feel you're defending your own territory. The testosterone surges in the goalkeepers was unbelievable and obviously they're the ones who are most involved in defence."
If coaches can use motivational techniques to boost testosterone before away matches, they should be able to improve their teams' scores, say Neave and Wolfson. But it is also important to study individual differences in testosterone levels, they say. "Some players go on the pitch and they go for it too hard, injuring themselves and others. We want to see whether there are also links between high testosterone levels in some players and subsequent poor performance in a match."
Wolfson and Neave studied players in the Under-19 squad of a UK Premiership team. They took saliva samples one hour before three training sessions, two away games and two home games. The players were matched with two separate opposition squads: one a bitter rival, one classed as a moderate rival. They played each rival once at home and once away.
The players' testosterone levels were at the male average before the training and away matches. But they were 40 per cent higher just before the match against the moderate rival and 67 per cent higher before the bitter rival match.
The goalkeepers showed the biggest variation in testosterone, says Wolfson. "In training, they had the lowest levels of the all the players, but before the home match, they had the highest. When playing the game, it looks as if the burden of responsibility falls upon them."
Other factors are likely to be involved in the home advantage. Crowd support, referee bias and familiarity with the pitch, have all been put forward as explanations. "But none of these on their own has been found to have a strong effect," says Wolfson.
Wolfson and Neave's research was presented at the annual conference of the British Psychological Society in Blackpool, Lancashire, UK.