Wednesday, September 22

The Ikea cafeteria (part 2)

I eat at fast food restaurants a lot. Usually, when I'm finished, I'll throw the remnants of my meal in the garbage and stack my tray neatly on top of the garbage can to be collected.

Why do I do this? It would be easier to me to leave my tray on the table for an employee to clean up — it is someone's job, after all. I think I do it for two reasons. First, it's a social norm. Other people do it, so I feel like I should do it. Second, I feel bad for the fast-food employees because they do a tough job for a tiny wage, and I feel a little better about myself if I help them out (although by this logic, I'd start tipping the guy who gives me fries, so maybe my motivation is more due to social norms than outright altruism).

At any rate, throwing out one's tray tends to be the unwritten rule at fast food outlets, which is why I was surprised to see it written out explicitly at the Ikea cafeteria in Ottawa:



This sign struck me as being ridiculous. It's a real-world illustration of the prisoner's dilemma, the most classic game-theory problem. In the prisoner's dilemma, two individuals can choose to either co-operate or defect. The best combined outcome is when they both co-operate. The catch is that if you co-operate, then I can defect and be better off. That leads game theorists to predict that both individuals will defect, even though they would each be better off if they could agree to co-operate.

The same thing holds for my Ikea tray. If everyone co-operates (by clearing their own table), we're all better off because Ikea can keep its prices low. But if I know everyone else is going to clear their own table, I'll leave mine in a mess because I like being lazy and because one table in isolation is not really going to affect Ikea's prices. If everyone thinks this way, no one will clear their table and Ikea will presumably have to jack up their food prices. This free-rider concept is also why we see a lack of action on global warming.

Ikea's sign is trying to appeal to the game theorist in us — it's trying to tell us that our dominant strategy (to use the game-theory lingo) is to clear our tray. But that's precisely what is so ridiculous about the sign; if we think about the game theory, as the sign urges us to do, our dominant strategy is actually to leave a heaping mess at our table for some poor employee to clean up.

Rather than try to appeal to people in terms of dollars and cents, Ikea would probably have better luck appealing to people's sense of social norms. A sign along the lines of "Don't be rude — clear your food!" would probably be far more successful at getting people to clear their trays than the existing sign.

This notion has been demonstrated empirically with the Israeli daycare study, which you might remember if you've read Freakonomics or Predictably Irrational. Economists figured more parents would pick their kids up from day care on time if the parents were fined for being late. But fines resulted in an increase in late pick-ups, presumably because the fine caused parents to no longer think in social norms ("I better pick my kid up on time because I'm supposed to") but to think of things in economic terms ("I can squeeze more time at work and only have to pay a few extra dollars to the daycare? Not a bad deal").

When you try to get people to follow a social norm by getting them to think about a problem in an economic sense, it can backfire.