Thursday, August 6, 2015

Obviously E. coli is a rational utility maximizer

Figure from An Economic Framework of Microbial Trade

I think this paper ("An Economic Framework of Microbial Trade." H/T Mark Thoma) presents a serious challenge to the dominant paradigm of human decision-making in economics (expectations about the future, weighing opportunity costs).

Tom Brown once asked me if my framework would apply to non-human markets. At the time, I didn't have any good examples and so couldn't answer. This paper provides one: a community of E. coli. The mathematical model the researchers set up in the paper is a utility maximizing framework, but generally similar results can be obtained from an entropy maximizing framework.

But E. coli doesn't really plan for the future. It doesn't really make decisions in that would be considered remotely  the same as a human deciding between two different brands of bacon. Yet it seems to be effectively rationally maximizing utility. Without a brain.

So maybe, just maybe that whole idea of rational humans maximizing utility saves the phenomena of economic exchange, but doesn't really explain what is going on?


  1. Interesting... I'm glad you found that. (Good memory, BTW)

    Here's another biology inspired piece.

    1. You mention "without a brain" ... and I'm not going to dispute that, but what is a brain anyway, except a machine to store and process information. So how can we say for sure that another system that stores and processes information doesn't have something analogous to a brain? I'm sure somebody has thought this through a lot more carefully than I have, but I always wonder if there are other "brain like processes" going on right under our noses that are so different or on such an entirely different time scale than our own brain process, that we just don't see it.

      I'm not necessarily advocating for such things existing... but I'm wondering how or if we can rule them out.

      I sometimes imagine that a termite, bee or ant colony might qualify... almost like a bunch of disembodied brain cells... passing some chemical signal around between individuals. How can we be sure that the colony as a whole can't be said to experience its environment in some manner (wholly alien to our own)?

    2. Hi Tom,

      I'd agree that a brain as such isn't necessary and brain-like functions could emerge from things without brains (I think Hofstadter uses a metaphor with ants in Godel Escher Bach -- although ants have brains).

      My point was that the normal "rational utility maximizing" Operating System (rum-OS) typically runs on a processor called a "brain". With E. coli we seem to be seeing the same output of the rum-OS running on a single transistor. That is to say that maybe the software behind the rum-OS isn't really that complicated and doesn't call the various functions of a brain like planning ahead or consciousness ...

      In the old x86 chips you could add a math co-processor. If a program ran as fast with or without the math co-processor, it probably wasn't using it. In the same way, the rum-OS probably isn't using much of the brain that couldn't be accomplished with a single neuron/cell.

    3. As is my habit, I thought it'd be fun to post a link to this elsewhere where a discussion of rationality was taking place. Ray Lopez took issue and brought up free will and Roger Penrose. I've never read Penrose's book, but I'd done a cursory look into his ideas on this before.

      My non-expert opinion is swayed by the argument that it's a stretch to say that quantum effects come into play at the scale of a neuron and what causes it to fire, especially in light of the fact that we've more or less successfully replaced them with deterministic machines in a few cases (e.g. cochlear implants). Why am I telling you this? Because I figure you may have an informed opinion.

      Also, you should be aware that Sumner took issue with your comment. And honestly I don't understand your comment either.

    4. I answered Sumner. I'm guessing he either 1) thinks human events are drawn from a distribution with a convergent mean and variance or 2) doesn't understand ratex requires you to be able to calculate a finite mean and variance.

      I don't think quantum mechanics has any real effect on how a human brain works. A lot of processes in neurons involve millions of neurotransmitter molecules and zillions of ions; it's hard enough to keep that many things in a quantum coherent state at absolute zero (nano-Kelvin).

      However! Quantum effects may be important in how particular proteins (and other molecules) work:


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