Important sources: George Ainslie

The place where I first encountered sustained discussion of the question whether there is, or must be, a common currency in which the values of options available to an agent are represented is the second chapter of George Ainslie's Breakdown of Will (Cambridge University Press, 2004). That chapter is called "The Dichotomy at the Root of Decision Science: Do We Make Choices By Desires or By Judgments?". In it, Ainslie surveys a variety of proposals for explaining ambivalence and addiction, drawn from various fields and periods in history. Many of them have in common that they suppose that the motivational system in an ambivalent individual must be fundamentally divided. Ainslie rejects these proposals, especially in his section (2.2) called "Does addiction come from processes that violate the usual laws of motivation?" That section contains a sub-section (2.2.3) called "There must be a single dimension of choice".

Ainslie directly and repeatedly invokes currency metaphors to make his arguments here. Saying, for example, that "Reason and passion must bid for control of the person’s behavior using the same kind of currency" (p25). It is in this sub-section that Ainslie quotes Peter Shizgal and Kent Conover, who wrote (in a paper that I'll discuss in more detail in a future posting):

For orderly choice to be possible, the utility of all competing resources must be represented on a single, common dimension. (Quoted in Ainslie, 2001, p25).

Breakdown of Will is in some ways a shortened and updated version of Ainslie's earlier Picoeconomics (Cambridge University Press, 1992). The second chapter of Picoeconomics is called "In search of the two minds" and it also includes two sections specifically concerned with common currency arguments. Section (2.2) is called "Multiple centres of choice must compete on a common basis", and section (2.3) is called "Separate principles of decision making must also compete".

In section (2.2) Ainslie discusses the view of Shwartz (The Battle for Human Nature, Norton, 1986) that "some sets of commodities are simply incomparable or incommensurable" (quoted in Ainslie, 1992, p30). Ainslie correctly recognizes that Schwartz is denying a common currency thesis, and responds as follows:

But if behaviors are not selected according to a single standard of choosability, the standard summarized by the term "reward" (or "reinforcement"), how are they selected? The organism’s means for expression are limited. A single channel of attention, if not a single set of muscles, is needed for the variety of behaviors that physically can be substituted for one another. Assuming that the selection of these behaviors is determinate, there must be a means of comparing them along a common dimension (Ainslie, 1992: p. 31).

There are more references to common currencies, and more emphatic arguments in favour of motivational commensurability, in both of the chapters I'm referring to here. Ainslie also discusses a wide range of sources, and considers a variety of objections to claims about motivational commensurability. The two chapters are, for these reasons, essential sources for anyone who is seriously interested in the common currency topic. (It doesn't hurt one bit that Ainslie is also a terrific writer.)

In later postings here I'll make some more critical and evaluative remarks on how Ainslie handles the common currency question. I'll also discuss some of the positions he criticizes. For now, I just want to draw attention to a pair of deep and interesting discussions, both relating to a set of questions I'm spending a lot of time thinking about.

Forthcoming attractions and related posts

Shizgal and Conover's 'orderly choice' argument.
Schwartz's arguments against motivational commensurability.
Critical discussion of Chapter 2 of Breakdown of Will.
Critical discussion of Chapter 2 of Picoeconomics.

[This list will be modified and extended as the related posts get published, and new links get added.]

Additional resources

George Ainslie's site www.picoeconomics.org has copies of many of Ainslie's papers. Most of them are focused on specific problems relating to intertemporal choice and hyperbolic discounting. But they include occasional remarks on the common currency question. (Among the resources on the site is a preprint of the Precis of Breakdown of Will, published in Behavioral and Brain Sciences (BBS) in 2005. You can find the preprint of the precis here. The final published version in BBS includes commentaries on the book, and Ainslie's reply. You can find it here, but you may find that it is behind a paywall.