Beyond the realms of dodgy lasagne served by an unfriendly chef on the sly, or stories of home fans blaring out loud music outside a travelling team's hotel room the night before an away match, the details, definitions and causes of home advantage can be hard to pin down.
Almost every fan has their anecdotes and ideas on what constitutes "home advantage" and how it affects their team. Players gain reputations for playing better when not required to travel. Stadiums become regarded more like fortifications than sporting venues. Managers lay siege and resist as the narrative requires and derby matches are counted up as invasions, especially when the away side manage to grab a heated victory in enemy territory.
But what is home advantage, where does it come from and how does it actually affect football players and matches on the field of play? To find out, Squawka have delved into the worlds of professional football and academia to discover its sources and place in the modern game.
All in the mind
Unibet's football ambassador and former England manager Glenn Hoddle has a greater insight into the effects of home advantage than most.
Over the course of a 40-year career in the game, as a player, coach and pundit, playing at various levels in the English and European game with Tottenham Hotspur, Monaco, Swindon Town and Chelsea, he has performed in front of a huge range of different home venues and crowds, but throughout these experiences one thing remain a constant.
“It's about the energy and the support that you're going to get,” he told Squawka. “Your pre-match is easier than travelling away, your dressing room is like a home and there's a feeling that every other week you're playing there.
“As players we went out onto that pitch believing that the crowd was behind us and you wanted to win for them as much as you did for yourself. It can lift you.”
Confidence, desire, passion -- whatever term fits as an adequate descriptor for the abstract, nebulous quality that can boost performances at home, it’s an intuitive if impossible-to-define answer to a the question of what causes the phenomenon of home advantage. And Glenn believes it’s particularly prevalent in football.
“There’s more of a tribal atmosphere than say tennis, golf or cricket and think I think if you have that behind you, you feed off it. That's really where it hits you, mentally. That's the reason why you see teams play better at home and have more chances of winning at home than away.”
In the 1966 World Cup, England played all their games at Wembley: the ultimate home advantage?
Another retired former England international has another theory, and as one of the team who used home advantage to win the nation’s one and only World Cup title in 1966, his proposal is worth hearing out.
For Sir Bobby Charlton, there’s more to making the most of the benefits of your own stadium than a boost in confidence and backing from the friendly faces and voices in the stands.
“It’s like being in your own house. You know exactly where everything is and precisely where you stand in relation to every piece of furniture,” he told the Mail in 2011.
“As a player, it’s the same geography. Your radar works off every landmark. For my generation, at first, it used to be the factory chimneys. You could see them from inside the ground.
“They were all different and when your brain picked them up from the corner of your eye as you were running you just knew instinctively how hard to hit the pass, precisely where to aim the shot, exactly when to send over the cross.
“Now it’s a curve in the seating line, the angle to the scoreboard, the lettering in the roof of the stand, the mouth of the dressing room tunnel. It’s subliminal.”
It’s another difficult concept to test, measure, prove or disprove, but recent research suggests there may be some more empirical evidence to support Charlton’s suggestion from within the realms of the academic world.
In 2011, Dr. Richard Pollard, a professor in the Department of Statistics at California Polytechnic State University, published a paper on how home advantage can be reduced when a team moves to a new stadium.
“Possible confounding factors, such as crowd size and crowd density, were considered but did not appear to have an effect. It is estimated that about 24% of the advantage of playing at home may be lost when a team relocates to a new facility,” he concluded.
Arsenal won 72.1% of their games in their final six seasons at Highbury compared with a win percentage of just 69.6% in their first six seasons at the Emirates, as per Arsenal.com.
It may be that as teams move, and players lose the old reference points that they once relied upon to get an edge through the scenery and conditions on home soil, they lose their home advantage. Examples in American sport are even more pronounced in the case of basketball courts with particular nooks and crannies home players know to use or avoid, ice rinks with an even surface or baseball stadiums featuring bizarre or unique dimensions or features.
Given how standardised football grounds and pitches have become, at least in relation to some of the professional games over the water, the landmarks that may be used by players would have to be more subtle. Still, stories of Brian Clough flooding the Nottingham Forest pitch before a vital home game in the European Cup, or visitors struggling against host sides more used to playing on artificial turf, or at altitude, such as Bolivia, are not uncommon.
In 2007, Bolivia, Ecuador and Colombia were banned from hosting FIFA World Cup qualifiers in their own capital cities due to altitude and the advantage it conferred to their players.
Yet the science isn’t conclusive, and regardless of Sir Bobby’s testimony, there are other competing theories as to how playing in front of your own fans is so beneficial.
Standing your ground
Home advantage and how it affects teams may come down to biochemistry, or more specifically pre-match testosterone levels. That’s the suggestion of Dr. Sandy Wolfson of Northumbria University, who tested the saliva of footballers before and after matches at home and away, and found that their testosterone levels were 40% higher than average prior to home games and 67% if their opponents were local rivals.
It could be that the boost Hoddle and other players experience when he stepped onto the pitch in front of his own fans was a natural spike of testosterone, inspired by more primal causes such as the desire to protect territory and defend your tribe and camp.
Given the hormone's effect on the human body and performance -- raising aggression levels, sharpening reflexes and shorten the recovery time after intense physical exercise -- players able to respond to playing at home in such a manner would stand to benefit.
Always territorial: as one of modern football's most combative characters and successful motivators, Jose Mourinho went 150 league games unbeaten at home between 2002 and 2011 at four different clubs.
There is a gender divide in football and home advantage too that appears to back up this theory. While there is a clear difference between home and away records in men’s football, in the women’s game, home advantage is far less pronounced. At the same time, men generally have higher levels of testosterone and naturally produce more of the hormone.
On top of any physiological factors, this idea of territory is important too. Many women’s team don’t have their own grounds, or are at least forced to share a stadium with reserves teams or men’s teams. It’s difficult to become truly territorial when you can’t lay claim to your own territory, which would also help to explain the dip in advantage for sides that have recently moved ground.
Dr. Wolfson made sure to record pre-match testosterone levels in the dressing room before players had walked out into the match day atmosphere so as to help rule out the influence of supporters, but there is evidence that home crowds may have an impact on performance.
That is the performance of officials, however.
A 2012 study by Professor Alan Nevill suggested that as crowd size increases, referees appear to subconsciously favour the home side, and in a low-scoring game such as football, just one or two decisions either way can ultimately have a huge effect on results.
Referees may be unwittingly influenced by crowds.
Writing in the European Journal of Sports Science in 2012, Chris Goumas even suggested that crowd density is more important than the size of the home support or even their proximity of the stands to the pitch.
Crowd noise could be another factor, and one that would help to explain why density may be a more influential than size. As many visitors to large stadiums such as Old Trafford can attest, sometimes, no matter how raucous the atmosphere in certain sections of the stands, the noise and intensity doesn’t always carry around. By comparison, the more concentrated composition of smaller grounds such as Selhurst Park can help to amplify the efforts of those trying to raise the volume.
Selhurst Park may be famous for its atmosphere but is it beneficial to Palace or an added source of pressure?
At least that's the theory. In reality, Crystal Palace have boasted a superior record away than at home since the start of last season. They were fifth on the away form table last term but only 16th for home form, and have won three away games this campaign compared to just two wins at home despite playing an extra game in front of their own fans. By comparison, the all-time league table for home win percentages are dominated by the usual suspects with their extra-large grounds: Manchester United on 74.05%, Arsenal with 63.53%, Chelsea on 62.95% and Liverpool with 61.07%
However, according to research by Christian Unkelbach and Daniel Memmert at the University of Heidelberg, loud crowd noise really can lead to a higher probability of yellow cards for fouls and other "in the moment" decisions through what is termed “cue learning”. The idea is that referees subconsciously come to learn to respond to the reactions of the crowd, although this could not account for potential bias over less instinctive judgements such as awarding additional extra-time to benefit the home side.
Home advantage: not what it once was?
With or without Mourinho, Chelsea went 86 games unbeaten at home between 2004 and 2008.
If home advantage can be put down to referees being influenced on top of the performance benefits of testosterone, territory and home players knowing their home turf, then it stands to reason that better trained, professional officials and higher refereeing standards should see part of this advantage decline.
And interestingly, research of football results since the end of World War II suggests that it really has dropped off. In a 2012 paper on the subject by Alan Nevill, he found that there has been a systematic decline in home advantage since 1945, with the steepest decline in lower divisions with smaller crowds.
Hoddle also believes that something has been lost with regards to home advantage, even in the decades since he was a player.
“On European nights there was probably 25% more,” he told Squawka. “The atmosphere under the lights, always being a night game in Europe, there was an added atmosphere, particularly at White Hart Lane. I think at Liverpool, Leeds, Arsenal and at Manchester United, all round, I think that was why we did so well in Europe back in the 1970s and 80s.”
To coin a phrase, an English team’s stadium was their castle, but perhaps that is no longer the case? At least not to the extent that it once was.
England isn't the only country were football's fortresses once stood even taller. During the 1960s Barcelona went 67 league games unbeaten at home.
Rule changes may have also had an effect too. According to an article by Paul Jacklin in 2005 for the Journal Of Sports Science, the upgrade of giving teams three points for a win rather than two in a league competitions has led to a “0.39 reduction in the ratio of home wins to away win.
“The evidence indicates that, in this particular context, the extent of home advantage has diminished. [...] I argue that this reduction is more likely to be the result of the introduction of three points for a win, which has lessened the incentives for away teams to settle for a draw.”
Or to put it another way, teams are more prepared to “go for it” and get at opponents away from home who they may have once settled for sitting back, defending and aiming for a draw. Even in recent years, as sides further down the Premier League pecking order have become emboldened by struggles at established top four clubs, such as Manchester United and Chelsea, a greater intent to go on the attack has seen some surprising away results. The reputations of stadiums such as Old Trafford and Stamford Bridge as impregnable fortresses may be something of a self-perpetuating confidence trick.
Under David Moyes, Manchester United struggled at home for goals and points, winning just 30 points compared to 34 points on the road in 2013/14.
In fact, the very idea of home advantage, and the influence of fans on their teams and results, may be overstated in the minds of those cheering and booing in an attempt to sway games one way or another.
A 2007 questionnaire organised by Dr. Wolfson asked 461 fans from across the English football league suggest that supporters rated their impact on matches as being far more influential than other factors, such as familiarity, travel, territory or referee bias. Season ticket holders were the group who felt most responsible for their team’s performances and results.
Meanwhile, the actual trend for results favouring the home team is one of decline. Perhaps the true fortresses of European football in the modern game lie on the fringes of the continent's cup competitions, as sides in the faraway, eastern territories of Russia and countries such as Kazakhstan and Azerbaijan, lead to energy-sapping plane journeys over multiple time zones, at least as far as clubs go.
International football is a different story, perhaps for similar reasons as to why the likes of Qarabag and Rubin Kazan, with national sides required to make similar trips to face their opponents abroad at each other's home stadiums, often on grounds of historical, political and cultural significance. At these venues, it's not hard to identify the potential benefits on offer, from territorial, testosterone-boosting anthems and media and crowd-born pressure on the officials.
Whether it's South Korea reaching the last four at the 2002 World Cup, Croatian players complaining over the soft decisions of the referee in their opening match of the 2014 tournament against hosts Brazil, or England's Wembley-centric march to victory in 1966, home advantage remains potent for countries even if clubs no longer feel the same effect.
As another international break filled with friendlies and play off games looms, it may be wise to back the house, even if the away sides of the Premier League and beyond are offering punters more value than ever.