Goalkeepers & the action bias

It's a cliche that goalkeepers are mad. But this new paper shows that they might also be plain wrong. A group of Israeli academics looked at a sample of penalty kicks from top matches around the world, and found that keepers' chances of saving them would be much higher if they stood still, rather than diving.
They estimate that a custodian of the onion bag who kept still would have a one-in-three chance of making a save, compared to a one-in-seven chance if he dived.
However, keepers very rarely stay put. In 93.7% of the 311 kicks studied, they dived, even though 28.7% of kicks went down the middle of the goal.
This suggests the best goalkeepers don't optimize their chances of saving spot-kicks. Why not?
There are several possibilities*.
One is that the purpose of diving is to put pressure on the striker. A striker who knows the keeper will dive must either aim for the corner of the goal or try to dummy the keeper, which adds to his chances of missing. But a striker who knew the keeper would stay put would possibly have an easier job.
Another possibility lies in the mix of social norm and regret minimization. A keeper who dives and fails to save a pen gets no blame. He's expected to dive and miss. But one who stays still and fails would get stick: "why didn't you try to save it?" he'd be asked.
Perhaps keepers put a higher priority upon not getting flak than upon maximizing their chances of saving. As Keynes said, it is better for one's reputation to fail conventionally than to succeed unconventionally.
This problem, though, might not be confined to goalkeepers. Governments and bosses are also expected to do things, even though inaction might be best. "Just stand there" might be good advice for them too.
* For example, a diving save looks great, and keepers value the small chance of this more than they do the bigger chance of a routine save. Or perhaps there's a social norm - revealed by the stick Nani got recently - against making one's opponents look stupid, which a standing save would do.

Comments

[William]

"inaction might be best"

Tell it to Gordon. He's just gone and banned plastic bags on the basis of some Newsnight show. Talk about twitchy.

[dearieme]

Since much the hardest shots to save are the low ones, shouldn't goalies lie down a lot?

[Matthew]

I remember Ron Atkinson making this point in the 2000 Euro championships and then all the penalties went in the corners.

Isn't there a problem in penalty shootouts, which if the players saw the 'keeper never moving, they would score rather easily. In fact if everyone adopted this, it wouldn't work, would it?

[Mike Woodhouse]

The trouble is that those in the governing business will equate doing less governing with adding less "value". And they would - these people didn't get where they are today by not doing something - they think they really do add value, Gawd help us. They action bias has worked in their favour so far.

And I suppose goalkeepers really need some randomising process when facing a penalty - once it's known that one always stands still there won't be many hit down the middle. We need more stats to construct a model that has Nash equilibrium.

Or just take them like the sainted Clive Mendonca - top corner and unsavable. Just requiring of a little more skill and bottle than usual.

[Luis Enrique]

I'm not going to read the paper* to find out whether they dealt with this, but the problem with empirical papers like this is they (probably) don't have a sample where goal keepers do actually start standing still, to see how penalty takers will react.

[I did write something wanky about repeated dynamic games with learning but sense prevailed]

* which would obviously violate the unwritten code of blog commentators

[JohnM]

Dearieme is right, the point is that goalkeepers have to behave unpredictably, which means diving most of the time. This way they will save a random number of penalties whereas if they stayed still, and the strikers knew they always stayed still, they would save none. Except, perhaps when Gareth Southgate was taking them.

[reason]

Why don't you analyse the people taking the penalties the same way? I had a friend in school who was a very good goalkeeper (Reserve to a National League team in Australia). He said he could never understand why the people taking the penalty didn't just blast it.

[dsquared]

there is a rather better paper on the same subject which demonstrates that goalkeepers (rationally) appear to behave as if they were playing a mixed strategy in a single-shot "chicken" game.

[Dirk Nachbar]

I think there is a confusion here, the probability of shooting in the middle is conditional on the belief the keeper will move. So the solution is much more complex, probably needs a bit of game theory.

[Scott Hughes]

I think it is not the only explanation, but I do think there is an action bias, as you say.

I also think the idea that if the goalkeepers always stayed still it would be easier for the person to make the shot because they would know. That probably happens in many cases where there is an action bias. The action helps indirectly by changing conditions.

It's probably not correct to compare action to hypothetical inaction because other factors would change too if there was inaction.

[technomist]

Lets face it - fear of peer group ridicule is a more powerful drive human drive than we give it credit for. I once jumped out of an aeroplane because I was more bothered by what people would say if I didn't than what my head was telling me about the (not yet experienced) dangers involved. Many goalies just don't want to look like an idiot who froze.

[scwr]

Time for ancient schoolmasterly joke about Coleridge's Ancient Mariner, possibly. Why was the Ancient M such a bad goal-keeper? Because 'he stoppeth one of three.'