Enough with the selfishness already

Here's a fairly interesting NYT article about an NYU game theorist. Too bad it still can't help but repeat one of the annoying little misconceptions about game theory (and perhaps economics in general):

Generally, game theory assumes that people are rational and selfish; they're always angling to get what's best for them, which means their behavior can often be predicted.

Repeat after me: game theory never assumes that people are selfish. It does assume they're rational; but rationality and selfishness are two different things. The selfish/selfless criterion applies to ends, whereas the rational/irrational criterion applies to means. For example, suppose your most important goal is to sacrifice your own life in order to save somebody else's. You find out you can be a donor for someone who needs a liver transplant but can't find a match and will die unless you donate. So you give them your liver and die saving their life. That's definitely not selfish behavior; but game theory would say it's rational. If, however, instead of doing that you'd participate as a victim in a human sacrifice ceremony meant to convince Jupiter to take your life instead of that other person's, that would be selfless and irrational.

The above-quoted sentence actually contains another error: it implies that it's the assumption of selfishness that's making it possible for human behavior to be (more or less) predictable. Not true. It's rationality that enables predictability; selfishness is completely superfluous.

To sum up: game theory does not assume people won't do selfless things. It assumes they won't do stupid things.