Friday, November 19, 2004

Buridan's Ass

At Oohlah's Blog-space, there are two recent posts (this one and that one) on "choice without preference" and Buridan's Ass. For those who are too lazy to click the links, here's the first of the two posts in its entirety:
In the first chapter of Jon Elster's Solomonic Judgments, he argues that choice without preference is not an important practical issue. He contends that no one cares which of two apparently identical soup cans on the supermarket shelf is chosen. The only way a choice like this will matter is if there are differences in the two soup cans, i.e., one has more broth than the other, etc.

I may have missed the point, but the problem of the choice without preference is that we can choose either soup can A or soup can B and satisfy our desire for buying soup. Since both soup cans will satisfy our desire, then rationality tells us to purchase both soup cans. If we think like this, though, we could potentially become poor very quickly. (Perhaps using the example of very similar cars on a new or used car lot would bring the problem to the fore.) So, it is not rational to purchase both cans. What seems to follow is that reason tells us to do something it is not rational to do.

Have I missed the point of choice without preference, or has Elster missed an important component of this difficult problem?
I may be stupid, but I'm like Elster -- I just don't see a problem here. The scenario assumes that our only motivation is to purchase the can, and that there are no constraints other than preference on choice. It ignores the motivation the post mentioned (the financial motivation to only buy one can), time-constraints, motor constraints, etc., which all factor in to the optimal (which is really what "rational" is in this case) choice. If you get rid of all of those, then there's probably no need to choose a can in the first place. In fact, I bet that if you threw all of those into an Ideal Observer model, what you'd find is that the model either chooses one of the two cans all of the time (which would probably be due to the motor constraints) or choose each can 50% of the time (because the motor constraint doesn't apply). Humans, because we're not ideal observers (our behavior is suboptimal) will have all sorts of noise in our data if forced to make the choice a bunch of times, but it would probably be pretty close to the ideal observer model assuming that the initial conditions were the same every time (which would be impossible, but you get the point).

Maybe Buridan's Ass is an interesting logical problem, even though it's not an interesting practical problem, and probably can't shed any light on the decision-making process (though it apparently sheds some light on Romance novels -- see here) other than that we have reasons for making decisions that go beyond the independent attractiveness of two options (duh!), but I can't imagine how it would be. For it to be even a logical problem would require that we pretty much remove all of the motivations to make the choice in the first place (a similar point for is made by Richard at Philosophy, etcetera). If it were still a problem, logical or otherwise, even given all of the constraints and other motivations that factor into a choice like this (or with them all removed), here's how I would solve it: I'd pick up both cans and then make a choice when I got to the cashier. By that time, choosing one should be more optimal than choosing the other (maybe because it's closer to me in the cart). I think that's pretty much the solution people much smarter than me have traditionally come up with (e.g., the solution of Otto Neurath, which just involved flipping a coin). As for the ass, since he probably doesn't have a shopping cart, or a coin, he's just going to have to suck it up and make a choice.


1 comment:

Anonymous said...

I think usually the primary point of Buridan's Ass is the question of what happens in the equilibrium case (i.e., in the case where the motivations interact so as to prevent action), to answer questions like, How precisely determined are our actions? (Most of the bloggers talking about it seem to have assumed that it approaches perfect precision, which actually does set up a paradox at an idealized equilibrium, in that the starving ass, undeniably motivated to eat something, would be unable actually to eat anything because there would be no 'slippage' - randomness, say, or indeterminacy - for acting one way or another. I don't think anyone's argued that this paradox is a contradiction, rather than simply something surprising that people might not want to accept without question. People often assume, too, that choice is of the optimal, and any number of other things. At the very least, the example gets some of these assumptions about the way decision-making works out in the open.)

I don't think this was the original point of the example in the Medieval period; the original point was, if I recall correctly (it's been a while) simply to say that in such idealized conditions the ass would starve, end of story, and this was intended to contrast with the human case (free choice). It does seem very difficult to get even determinists to admit even the remote in-principle possibility of an equilibrium state for human decision like that they often allow to be remotely possible in principle for an ass; everyone tries to wriggle out of it. I'm not sure most of them have any good reason for doing so - yes, the human case is vastly more complex, but that of itself doesn't prevent there being the possibility, however remote, of some equilibrium state, however complex. If there is such a possibility, however, remote, the reason why there is tells us something about human motivation and decision (for instance, that we have no ability to randomize on our own, that in any given case we are determined to one action alone, that 'choice without preference' may well be a contradiction, in which case choice seems to collapse into preference, etc.); and if there isn't, then the reason why there isn't tells us something about human motivation and decision (depending on what aspect of decision-making actually circumvents or prevents equilibrium).

But I think it's certainly true that there's no practical issue here. 

Posted by Brandon