The prisoners' dilemma, and why we all have to be kept in lockdown

The prisoners' dilemma is probably the most famous example of game theory in action. I've written about it many times, in many different contexts (for example here, here, here, and here). In the prisoners' dilemma, all players have a dominant strategy, which is a strategy that is always better for the player, no matter what any of the other players choose to do. However, if each player acts in their own self-interest, the outcome leads to payoffs that are worse for everyone, than if they had cooperated. Robert Frank has described these games as leading to behaviour that is 'smart for one, dumb for all'.

And you can see this sort of behaviour all the time (once you know what to look for). Consider the current lockdown situation in New Zealand. If the lockdown was in any way voluntary (as it effectively was until Wednesday night), then each person has two options: (1) stay home; or (2) act normally. For most people, acting normally is a dominant strategy, at least in the early stages of the coronavirus spreading. They are better off acting normally if everyone else stays home (because they mostly get to go on with their lives as normal, and have low risk of catching the coronavirus; whereas staying home they would be giving up on things they like to do), and they are better off acting normally if everyone else is acting normally (because life goes on as normal, rather than giving up on things they like to do). So, individually people are better off acting normally. And so we saw things like this:

Hundreds of partygoers ignored the Government's advice and crowded into Wellington bars on Saturday night with no social distancing in sight.

Just hours after prime minister Jacinda Ardern confirmed the country was on a level two alert and urged people to work from home and keep a safe two metre distance from each other, young revellers took to bars around the country...

There were also reports of bars in other main cities including Auckland and Hamilton teeming with people.

And around the world:

Young German adults hold "corona parties" and cough towards older people.

A Spanish man leashes a goat to go for a walk to skirt confinement orders.

From France to Florida to Australia, kitesurfers, university students and others crowd the beaches...

"Some consider they're little heroes when they break the rules," French Interior Minister Christophe Castaner said. "Well, no. You're an imbecile, and especially a threat to yourself." 

These people aren't stupid. They are selfish, and acting in their own self-interest. Which is why we needed to go into full lockdown, and early, if we wanted to curtail the spread of coronavirus. Any voluntary or partial measures would simply be subject to the prisoners' dilemma. As I've noted before, in a repeated prisoners' dilemma (which this is, because we are essentially repeating it every day for the next four weeks), cooperation requires trust. And collectively, our behaviour up to this point hasn't earned that trust. We need to be locked down, so that the dominant strategy was no longer available to us.

Finally, an interesting research project for later would be to look at the difference in response, and the effectiveness of response, between countries that are more authoritarian and those that are more democratic, and between countries where the average 'respect for authority' (for want of a better term) is high or low. Even looking at the early data on the countries where the spread has been curtailed relatively quickly (China, South Korea) and those where it hasn't (Italy, Spain), I think we can see a pattern forming.