Monday, May 20, 2013

Things that get suggested as common currencies

One of the things that makes the common currency topic interesting, is the variety of candidate currencies that get suggested.

Here is a list, that I’ll add to and flesh out periodically, of things that have been proposed as currencies:


In one of the economists’ technical senses, utility is not a psychological notion, but refers to whatever an agents behaviour tends to make more probable, as revealed in the pattern of behaviour itself.

An ‘agent’ on this view is anything whose activity reveals a consistent set of preferences, although additional assumptions can be introduced so that apparently inconsistent entities still turn out to be agents.

A consistent set of preferences revealed by an agent, represents the common currency of that agent. (Any two options will stand in some relation of relative preferability.)

There are other technical notions of utility (for example from behavioural economics) that I’ll list here in the future.


This is reinforcement in the behavioural psychologists' sense, where a reinforcer is something that changes the rate at which a behaviour is emitted. (In proper terminology it is behaviours that are reinforced, while agents are rewarded.)

So the various reinforcement values of all things that are reinforcing will also define a common currency, representing the effectiveness of all the incentives to which an agent is responsive.

An exemplary statement of the argument for a common currency in this setting is the following:
"In natural settings, the goals competing for behavior are complex, multidimensional objects and outcomes. Yet, for orderly choice to be possible, the utility of all competing resources must be represented on a single, common dimension" (Shizgal & Conover 1996).
There's a discussion of Shizgal and Conover's paper here.

Pain and Pleasure

I have not read this book.

According to Bentham pain and pleasure were the “two sovereign masters” which both explained human action, and enabled good and bad consequences of actions to be identified. Contemporary economics and behavioural psychology make considerably less reference to pleasure and pain than a Benthamite might have expected. Instead they focus on largely behavioural notions of utility and reward. Among those whose primary interest is pleasure and pain, one still finds suggestions that these constitute a ‘common currency’:
“Consistent with the idea that a common currency of emotion enables the comparison of pain and pleasure in the brain, the evidence reviewed here points to there being extensive overlap in the neural circuitry and chemistry of pain and pleasure processing at the systems level.” (Leknes & Tracey, 2008, p314).


Fitness is (roughly and informally) relative propensity to have descendants. It is relative to competing variants in a population, and so typically defined by reference to genotypes.

If we focus specifically on the contribution to fitness of the behaviour of an individual, then we might go on to think that the contribution of individual behaviours (or behavioural dispositions) might be ordered with respect to how much the add or, or undermine, total fitness. Something along these lines is one goals of at least some behavioural ecologists:

“Any attempt to understand behavior in terms of the evolutionary advantage that it might confer has to find a "common currency" for comparing the costs and benefits of various alternative courses of action” (McNamara and Houston 1986: 358).


ATP is the standard abbreviation for Adenosine triphosphate. It’s the molecule used to transport energy in cells. It might seem like an odd thing to have on this list, although it is common to hear it referred to as the ‘energy currency’ of intracellular processes. Since any behavior has some energy cost (or gain), and any allocation of metabolic resources has an opportunity cost (in actions rendered unavailable, or made possible) it’s plausible to think that in a highly aggregated way, ATP represents an important overall budgetary bottom line.

Quite how to relate this to some of the other proposed currencies is another matter.


Leknes, S. and Tracey, I. (2008) A common neurobiology for pain and pleasure, Nature reviews: Neuroscience, 9,  pp314-320. [Publisher link.] [Google scholar citations.]

McNamara, J.M. and Houston, A.I. (1986) The Common Currency for Behavioral Decisions, The American Naturalist, 127(3), pp358-378. [Publisher link.] [Google scholar citations.]

Shizgal, P. & Conover, K. 1998. On the neural computation of utility, Current Directions in Psychological Science, 5(2), pp. 37-43. [Publisher’s site –may be behind a paywall] [Preprint version at CogPrints] [Google Scholar Citations]

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