Tuesday, June 28, 2011

The biology and economics of home advantage

Every few years, the Fotherington-Thomases at the London Review of Books give David Runciman a break from writing about the sorry state of British political life, and let him indulge an apparent obsession with José Mourinho.

In the current issue, where he reviews Scorecasting by Tobias Moskowitz and Jon Wertheim, Runcimann uses the astonishing record of Mourinho’s teams – he went nine years at Porto, Chelsea, Inter and Real Madrid without losing a home league game – as a springboard to discuss the mysteries of home advantage.

Runcimann doesn’t like Moskowitz and Wertheim’s idea that teams win more at home because crowd pressure makes the officials biased in their favour. Or at least, he doubts that it’s the whole story. But I think he’s too quick to dismiss alternative ideas and declare the whole thing a mystery.

He’s no faith, for example, in the benefits of local knowledge:

What about local knowledge? Every ground is slightly different, so perhaps teams take advantage of their familiarity with their home environment. Even football pitches vary: some are wider, some are narrower, some are blowy, some are sheltered, some are rough, some are smooth. The differences are most noticeable in baseball, where some teams play at stadiums that suit hitters, and others at stadiums that suit pitchers (it’s a question of size, shape and atmospherics). Yet even in baseball, Moskowitz and Wertheim find it makes no difference. Teams that play in hitter-friendly stadiums do not outhit their opponents by any greater margin than teams that play in pitcher-friendly stadiums. This despite the fact that managers can pack the team with sluggers, sure that they will play at least half their games in advantageous conditions. Knowing what you need to do well in your own yard doesn’t help you do it any better. Home advantage seems to be entirely outside anyone’s power to control.

I’m no baseball expert, but I’d guess that in comparison with some other sports, environment doesn’t matter very much. What matters is the confrontation between pitcher and hitter, which is perhaps not very susceptible to outside influences. It’s interesting that home advantage is weak in baseball – the home side wins 54% of the time, compared with 60%+ for football.

Contrast that with cricket, where, because the ball bounces before it meets the batsman, local conditions make a huge difference. The slow, dusty wickets in India reward different skills to a hard and bouncy Australian track, or a Headingley greentop on a damp morning in May. Touring players often struggle to adjust their games to different conditions, which gives the natives a big advantage. (This despite the fact that official bias ought to be weaker, because cricket umpires are a long way from the fans, and the game’s manners are relatively good.)

Runcimann also suggests that home advantage might only apply to team games:

What if home advantage is a team phenomenon? There is plenty of evidence not considered by Moskowitz and Wertheim to suggest that it is. British tennis players have never seemed to gain much advantage playing at Wimbledon, despite the presence of thousands of people willing balls that are in to be called out (I’m talking pre-Hawk-Eye here). Are phlegmatic British line judges somehow impervious to these pressures in a way that football referees are not? It’s not just us Brits. No Frenchman has won the French Open since 1983; no Australian has won the Australian Open since 1976. Where’s the home advantage? One explanation might be that playing at home really makes a difference only when you’re part of a team. It’s a collective experience, in which case it dissipates for isolated individuals (including the individuals standing at the free-throw line in a basketball game or at the penalty spot in a football match). Somehow, playing at home breeds a sense of solidarity, or what used to be called team spirit, which means that players have more confidence in each other and work better as a unit. I’m not saying that’s definitely what happens. But Moskowitz and Wertheim haven’t proved that it doesn’t.

But again, it’s not the officials or some mysterious collective solidarity that are important here, but familiarity with the conditions. British players play Wimbledon once a year, just like anyone else. They might have the crowd behind them (although this might just make them nervous, and individual sports like tennis don’t lend themselves to the tribal devotions of team sports like football), but they don’t know the place any better.

Instead, like cricketers, specialize on the surface they grew up on or the one that best suits their game. Rafael Nadal is all but unbeatable on clay, the same went for Pete Sampras on grass. To a lesser extent, this is true of golf, where links courses demand a different type of game to those inland.

If you play a chase-ball game like football or basketball, your playing environment will be less variable. On the other hand, you’ll play fully half of your games at your home stadium, whereas your opponents will only visit it a handful of times a season. This will make you much more familiar with the surface, the dimensions of the pitch, the visual and acoustic environment, and so on. You become a specialist at playing at home, even if you can’t put your finger on what that specialism entails. You also become worse at playing away, where things are different.

It’s be interesting to know how home advantage varies between teams (although it’d be difficult to control for other factors – could you make other-things-being-equal pairs?). Mourinho has a superb eye for detail, an ability to make little things work in his favour, and a knack for nullifying the opposition, which might help him to maximize home advantage.

Besides specialism, there’s another biological/economic phenomenon that might be an even more important contributor to home advantage in sport. In territorial contests, the incumbent is most likely to win. This goes for male speckled wood butterflies fighting over sunny spots in a woodland, where (Mourinho-like) the resident always wins, and groups of feral horses contesting access for waterholes, where the incumbent wins 80% of the time.

Two psychological biases in humans also give incumbents an advantage in contests over territory or resources: the endowment affect – people value a thing more when they possess it than when they don’t – and, related to this, loss aversion.

So, in the words of a paper by the economist Herbert Gintis, incumbents are "willing to expend more resources to hold the resource than the intruder is to seize it."

Gintis goes on to model the conditions that lead to property rights, where challengers, be they animals or people, decline from fighting incumbents.

It seems plausible that the endowment effect and loss aversion are also at work in sport. The home team is the incumbent - it is defending its patch. It values winning more than the visitor, and so tries harder and wins more often.

Monday, June 13, 2011

Recommend a blog, win a book

When you write a book, the publisher sends you a questionnaire asking about promotional opportunities, on which you write down all your big-name author friends who will big-up your work, and all your TV-presenter buddies who will have you on their show.

I'm filling out the questionnaire for my forthcoming book, 'People Will Talk: The Science of Reputation' at present, and it's looking blank. So I'm hoping that someone reading this can recommend blogs to send a promotional copy.

The book is rooted in evolutionary biology, and branches out into all kinds of other stuff - online society, international relations, social networks, animal behaviour, social psychology, economics.

So what I'm looking for is tips on the top places on evo psych, (behavioural) economics, social networks (and capital), animal behaviour, business and brand-building, and so on - almost anywhere at the boundary of the social and natural sciences - who might be interested in the book and might want to review it.

I'd like to reward the person who sends the best recommendation(s) - based on how well they match the book, and how much I like the writing - with a copy of the book, which should be out in the autumn. I'll even sign it if you like, thus slightly lowering its resale value. A couple of rules for entrants:

1. I don't know you. If I do, please do send your recommendations, but either you can buy a copy, or I'll give you one anyway. You're not getting the prize.

2. I haven't heard of the site you mention. You'll have to take my word on this one. I'm not a big blog reader, but I think I'm aware of most of the big ones in evolution. I also know a few of the economics ones (crookedtimber.org and Marginal Revolution). Besides revealing promotional opportunities, I'm hoping that this exercise will broaden my mind.

Please leave suggestions as comments, or tweet me: @gentraso. (I'm not online every day, so don't be cross if I don't respond immediately.)