|Old illustration of Buridan's Ass (famously indifferent between two food options).|
If you’re struggling for a rough sense of what the hell I’m talking about on this site, then this post is supposed to help. It’s deliberately non-technical and informal. My aim is to give a fairly general and intuitive sense of the idea of a common currency, and avoid the technical details that go with how that concept is regimented in various sciences.
Consider any two things that you want. Here are some possibilities:
- You want each of them to about the same degree.
- You want one of them more than you want the other.
- There’s no fact of the matter about how(or whether) the degree to which you want them differs.
Now suppose that either option (1) or (2) applies not just to the particular two things that you initially imagined, but to every possible pair of things taken from the whole set (possibly infinite) of things that you want.
Then your wants would form a kind of list (possibly infinite), where every item on the list had a definite ranking (perhaps with some on the same rankings).
Those rankings would form a kind of common currency, like positions in a race (first, second, third, etc.). It would be common because everything you want would be somewhere on it.
It’s important that the ranking should include things that you don’t want too, because (a) you should want them less than things you positively want (possibility 1 or 2 above should apply to each of them), and (b) because they’re not all equally horrid. This means that we can (if we want) imagine the ranking to represent the net desirability of the things on it. (So a cupcake that costs ten dollars, or ten minutes of effort, could come lower than the very same cupcake for one dollar, or one minute of effort.) But we could also represent the costs as negative wants on their own, and suppose that net desirability is calculated (by subtracting costs from outcomes). Those are different ways of representing the same information.
We might imagine that the strengths of our wants are a little more quantitative. So, I might say not merely that I want a cup of coffee more than I want a glass of water, but that I want a cup of coffee twice as much as a glass of water. If every pair of our wants stood in this kind of relationship, then they would all have definite relative degrees of desirability. This would give a similarly common scale, but one that includes information about the relative sizes of the gaps between positions.
There are at least two ways of thinking about this ‘common currency’ scale, or dimension:
- In one case, it is a set of facts about the pattern in the actual choices you make. (One way of thinking of this is to suppose that an economist or behavioural researcher had observed a lot your activity and inferred the relative value of different outcomes from your choices. Such researchers might at least be agnostic about is be going on inside you. Many economists and behaviourists are officially agnostic about the inside, even though they’re committed to common currencies.) I’ve explained elsewhere on this blog that I find it useful to call this kind of “pattern in choices” currency ultimate.
- In the other case, it is a set of facts about the processes by which your choices are generated. One way to think about this is to think that your wants, or desires, or preferences, are real psychological states of yours. Another (which need not be the same thing) is to suppose that the strengths of your wants are represented in neural activity in your brain. I’ve explained elsewhere on this blog that I find it useful to call this kind of “process producing choices” currency proximal.
It turns out that scientists of various kinds (including behavioural ecologists, economists, behavioural psychologists, and neuroeconomists) argue that there is a common currency for at least some kinds of agent. But they sometimes argue for ultimate currencies, and sometimes proximal ones, and they use different kinds of evidence and theory to defend their positions.
It’s also not difficult to find examples of people denying that there is a common currency. Some deny it for humans, partly because they find it offensive to suppose that our most noble wants might appear on the same scale as our most base ones. Some deny it for some classes of animal or robot, usually saying that internal representations (including of strength of preference) aren’t necessary for orderly behaviour.
I’m interested in the tangle of claim and counter-claim that this combination of arguments in favour and against produces, when looked at comparatively. To get an idea of what I’m working on see My OwnEfforts and the links there.
Important Sources: Rodney Brooks – Denies representations for at least some robots, so denies proximal currency.
Important Sources: Kim Sterelny – Seems to hold a position sharing some key features with Brooks.
Important Sources: George Ainslie – Staunch defender of common currency thesis.