The Hawks’ nest: The science behind home ground advantage

Avan Stallard Roar Rookie

By , Avan Stallard is a Roar Rookie

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    As long as sport has been played, fans have known about home ground advantage.

    In the AFL, the journey to Subiaco Oval to play Fremantle or West Coast was long considered the most daunting road trip. But, since 2014, another stadium has held the title of most fearsome venue: Adelaide Oval.

    Particularly at Port Power games, opposition players talk about the deafening wall of noise that assaults them on the field. It is precisely as intended. In a redevelopment completed in time for the 2014 season, Adelaide Oval’s playing surface was lowered by one metre and a third tier was added to the stands. A semi-dome reminiscent of a sailor’s cap now sits atop the southern grandstand end. The combined effect is for crowd noise to be trapped and amplified.

    Since its unveiling – perhaps unleashing would be a better word – the acoustic properties of the new stadium have been more in keeping with Roman amphitheatres than suburban footy fields. 20,000 enthusiastic Port fans sound like a hundred thousand warring Spartans.

    It could be no more than coincidence, but in 2014 the Power enjoyed a remarkable streak of home game form, with a winning ratio of 9:2. In away games that ratio dropped to 5:6. That is, Port were 36% more likely to win at home than away.

    This Saturday, the Hawks take on the Eagles for the AFL premiership. The Hawks have emerged as clear favourites.

    There is good reason for this. The Hawks have proven ability across four recent grand final appearances, an enormous advantage in finals experience among players and coaching staff, and they are league leaders in attacking form as measured by points scored.

    There’s also one other little thing. The Hawks are playing at home.

    As tradition and an iron-clad contract dictates, the grand final will be played at the MCG, which happens to be the Hawks’ home ground in Melbourne (though, technically, it is not considered a home game). The Eagles, on the other hand, will be flying 3000 kilometres to a hostile reception. The question is, does this afford the Hawks an advantage? Does playing at home really make a difference?

    The answer – not just according to punters, players, mums and coaches, but according to sports scientists, economists and psychologists – is an unequivocal ‘yes’. University of Rochester psychologist Jeremy Jamieson conducted a meta-analysis of scholarly studies examining home ground advantage.

    Collating the statistics, Jamieson found that, on average, a home team wins 60% of the time. That might sound negligible, but, statistically, it is a major effect well beyond the realms of statistical error.

    In the context of AFL, a 2005 study by economist Stephen Clarke and a 2013 study by economist John Watson both show distinct winning advantages to home teams. Non-Victorian teams enjoy the largest home ground advantages, probably because Victorian teams that play in Victoria are not nearly so far out of their comfort zones travelling across suburbs as across states.

    To AFL supporters, such findings probably come as little surprise. Indeed, it’s considered axiomatic that playing at home is the biggest advantage going. When a team sells a home game to another venue – which numerous teams have done in recent years, as when Richmond sold a 2011 home game to play in Darwin (a match they lost) – it infuriates supporters.

    Not only are supporters denied the opportunity to watch the game in person, they no longer imagine themselves as having any influence over the outcome. The footy supporters, not always known for their unbiased opinions, have a point. It turns out that fans really do influence the game.

    There’s any number of folk theories as to exactly why a team’s home ground confers an advantage. It’s often said that home team players know the ground and conditions better (i.e., grass on dirt; size of the oval; where the toilets are).

    They don’t have to travel, which can drain energy, focus, enthusiasm. They get to sleep in their own beds (think princess and the pea and AFL footballers). They enjoy a home-cooked dinner and breakfast (whereas a hotel buffet couldn’t possibly be as caloric, delicious or psychically nourishing).

    None of these explanations hold water under scrutiny. The research, however, has been able to finger two other factors: player testosterone and referee bias.

    Testosterone boosts aggression, power and work rate. Psychologists Nick Neave and Sandy Wolfson measured testosterone levels in football players during training and then immediately before both home and away games. They found little difference between testosterone levels during training and away games, but a remarkable spike in testosterone at home games.

    This means that home teams – spurred by supporters and the knowledge they are protecting the home turf – are able to tap into greater aggression and explosive power. From an evolutionary standpoint this makes good sense. When our primate ancestors were contemplating hostility with rival tribes, a boost to performance could be the difference between survival and perhaps even widening one’s access to resources, as opposed to death, injury, or loss of territory.

    But, importantly, boosting testosterone and the consequent will to fight only made sense on home turf – where our ancestors were likely to have the advantage of both knowledge and numbers. If, however, our ancestors found themselves in foreign territory, facing a group of aggressive competitors, a surge of testosterone that encouraged them to stand and fight could only have raised the odds of injury or death without gain.

    Evolutionary psychologist Robert Trivers boils the anomaly down to this: ‘Motivation is stronger to protect what you have than to seize what you don’t.’

    For away team athletes, though they may consciously will themselves to victory on rival turf, there is no way to counter the real effects of increased psychological aggression and physical power experienced by their home team opponents.

    The other source of advantage to home teams – referee bias – is perhaps the more counter-intuitive because it runs against the interests of the perpetrators (as in, the refs).

    In Scorecasting, Tobias Moskowitz and Jon Wertheim document a wealth of data tallying referee errors across multiple sports. Their results will surely feel like vindication to countless fans who’ve said as much for years: the referees are biased.

    But it’s precisely how that matters: referees are consistently biased in favour of the home team.

    In baseball, gridiron, ice hockey, basketball, boxing and football leagues the finding is the same. Referees tend to make more errors in favour of the home team than in favour of the away team. John Watson’s 2013 study shows that the same is true of the AFL.

    A hint as to what triggers this behaviour in referees is provided by a remarkable real-life situation that doubled as a controlled experiment. In 2007, rioting at Italian football games led to the Italian government imposing strict security requirements on clubs. Those without adequate security were forced to play in empty stadiums.

    As a consequence, 21 games were played to silence. Economists then analysed the crowd-less games and compared them to games played in front of a crowd – same teams, same referees.

    The result was stark. When the stadiums were emptied of supporters, bias in referee calls in favour of the home team dropped between 23 and 70 percent for different types of fouls.

    As Merskowitz and Wertheim state: “That is, the same referee overseeing the same two teams in the same stadium behaved dramatically differently when spectators were present versus when no one was watching.”

    In another controlled study of football fouls, two groups of referees were shown footage of tackles: one group with the noise of the crowd turned on, the other group with crowd noise muted. Referees who viewed the tackles with the crowd noise turned on were more likely to make a call reflecting the opinion of the crowd than referees who viewed the tackles on mute. He who yells loudest holds the most sway.

    Research by Thomas Domen further supports this finding. Domen found that referee bias was less pronounced at football home games where the field had a running track surrounding it. The further away the marauding crowd, the less a referee is influenced.

    But why? Why should referees be biased when their version of the Hippocratic Oath is to be impartial – and the longevity of their careers depend on their being so?

    Simple. The bias is unconscious.

    It’s not that referees are dastardly fiends who act upon pernicious motives; they neither want to make biased calls nor know that they in fact do so. It’s that the conscious ‘referee’ modules of their brains are imperfectly synchronised with the unconscious modules of their brains that are programmed to favour the crowd.

    As evolutionary psychologist Robert Kurzban argues, the brain contains many modules with different functions, some conscious, some unconscious. Processes in one module are often completely cut off from processes in another module.

    In other words, conscious modules of a referee’s brain genuinely want to be unbiased, but other modules insist on listening to and conforming to the crowd.

    This also makes sense from an evolutionary standpoint. Agreeing with and currying favour with the dominant group, especially when that group is aggressive, would have afforded that individual better chances of survival and thus better chances of passing on his or her genes.

    It’s also true that in uncertain situations humans are hard-wired to seek the wisdom of the majority, a decision-making technique that has the unexpected boon of being correct more often than not (though not in sports).

    Our brains, evolved across millennia for the sole purpose of out-competing and out-reproducing rivals, the same brains found in the heads of modern humans and modern referees, is simply not equipped for the nuances of unbiased refereeing.

    Between player testosterone and referee bias we are therefore able, theoretically, at least, to explain the remarkable advantage experienced by Port Power at Adelaide Oval. The unique design of the ground and stands amplifies the sound of a fanatical group of supporters. Port players experience a surge of testosterone that improves multiple aspects of their game, while referees are unconsciously compelled to make errors in favour of the Power.

    So, to the question that matters: do the Hawks take a home advantage into the 2015 grand final?

    Probably. The MCG is the Hawks’ home ground. We evolved to defend the home ground with might and craftiness, regardless of right and reason. On game day, the Hawks players will experience a surge in testosterone, resulting in heightened aggression, power, and work rate.

    However, research also suggests that high stakes games and games between intense rivals correlates with a spike in away team aggression. Thus, on the most important day in their football-playing careers, the Eagles players can be expected to have higher than usual testosterone levels, reducing the overall advantage of the Hawks.

    As for unconscious referee bias, it is a fact that there will be more Hawthorn than Eagles supporters in attendance due to the ticketing allocations between MCG members, club members, and the public. The roar of a full MCG – around 100,000 fans – is an awesome thing.

    Those fans will be cheering loudest for Hawthorn, and booing or screaming loudest when they see what they judge to be an infringement by West Coast players. Though the umpires will be the AFL’s best, they are only human.

    We’ve seen that much in recent days. During West Coast’s preliminary final against North Melbourne, played at Subiaco oval, the three most important (in terms of advantage) and most blatantly incorrect decisions went in favour of the home team, as Rohan Connolly pointed out in his analysis of the game for The Age.

    In the second quarter of the match the Eagles’ Luke Shuey picked up the ball, dropped his head and torpedoed himself into Nick Dal Santo, in this case an innocent bystander. A free kick was awarded – to Shuey – who subsequently goaled, reducing the Roos’ lead to five points.

    In the third quarter, the Eagles’ Jack Darling was awarded a free kick against Robbie Tarrant for holding. Replays showed no holding, nor anything that could be reasonably construed as holding. Darling goaled. In the fourth quarter, the Roos’ Ben Jacobs was fifteen metres out, directly in front of goal, when he was legged by Shuey, a clear case of either tripping or tunnelling.

    The umpire called play on and the Eagles cleared the ball out of the 50.

    A fourth egregious error that rendered less advantage came in the second quarter when Roos’ captain Andrew Swallow was illegally tackled around the neck while standing a mark. The umpire was heard to say to an incredulous Swallow: “No, no that’s okay.” The crowd thought so, too.

    On Saturday, everything we know about umpires (and humans) suggests there will probably be a few more questionable decisions that go the Hawks’ way than the Eagles’. Will it be enough advantage for them to win?

    There is no way to know. A small home ground advantage is quickly rendered irrelevant by one simple factor: greater skill. In a close game it could be the decider… or not. But whatever the outcome, supporters will always have their suspicions.

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