Something about cyclists seems to provoke fury in other road users. If you doubt this, try a search for the word "cyclist" on Twitter. As I write this one of the latest tweets is this: "Had enough of cyclists today! Just wanna ram them with my car." This kind of sentiment would get people locked up if directed against an ethnic minority or religion, but it seems to be fair game, in many people's minds, when directed against cyclists. Why all the rage?
I've got a theory, of course. It's not because cyclists are annoying. It isn't even because we have a selective memory for that one stand-out annoying cyclist over the hundreds of boring, non-annoying ones (although that probably is a factor). No, my theory is that motorists hate cyclists because they think they offend the moral order.
Driving is a very moral activity – there are rules of the road, both legal and informal, and there are good and bad drivers. The whole intricate dance of the rush-hour junction only works because people know the rules and by-and-large follow them: keeping in lane; indicating properly; first her turn, now mine, now yours. Then along come cyclists, innocently following what they see are the rules of the road, but doing things that drivers aren't allowed to: overtaking queues of cars, moving at well below the speed limit or undertaking on the inside.
You could argue that driving is like so much of social life, it’s a game of coordination where we have to rely on each other to do the right thing. And like all games, there's an incentive to cheat. If everyone else is taking their turn, you can jump the queue. If everyone else is paying their taxes you can dodge them, and you'll still get all the benefits of roads and police.
In economics and evolution this is known as the "free rider problem"; if you create a common benefit – like taxes or orderly roads – what's to stop some people reaping the benefit without paying their dues? The free rider problem creates a paradox for those who study evolution, because in a world of selfish genes it appears to make cooperation unlikely. Even if a bunch of selfish individuals (or genes) recognise the benefit of coming together to co-operate with each other, once the collective good has been created it is rational, in a sense, for everyone to start trying to freeload off the collective. This makes any cooperation prone to collapse. In small societies you can rely on cooperating with your friends, or kin, but as a society grows the problem of free-riding looms larger and larger.
Humans seem to have evolved one way of enforcing order onto potentially chaotic social arrangements. This is known as "altruistic punishment", a term used by Ernst Fehr and Simon Gachter in a landmark paper published in 2002. An altruistic punishment is a punishment that costs you as an individual, but doesn't bring any direct benefit. As an example, imagine I'm at a football match and I see someone climb in without buying a ticket. I could sit and enjoy the game (at no cost to myself), or I could try to find security to have the guy thrown out (at the cost of missing some of the game). That would be altruistic punishment.
Altruistic punishment, Fehr and Gachter reasoned, might just be the spark that makes groups of unrelated strangers co-operate. To test this they created a co-operation game played by constantly shifting groups of volunteers, who never meet – they played the game from a computer in a private booth. The volunteers played for real money, which they knew they would take away at the end of the experiment. On each round of the game each player received 20 credits, and could choose to contribute up to this amount to a group project. After everyone had chipped in (or not), everybody (regardless of investment) got 40% of the collective pot.