The Future of Everything

January 12, 2018

Aeon piece on quantum economics – responses

Filed under: Economics, Physics — David @ 12:32 pm

Thanks to readers for taking the time to comment (via Twitter) on my recent Aeon piece Economics is quantum. Since it is hard to reply in strings of 140 characters, this post addresses some of the questions and criticisms that came up (edited for clarity).

After physicist Richard Jones wrote that the piece was “confused & misleading” (not a completely unusual reaction, I must admit) I asked him to clarify which parts of the text he was referring to. 

Jones: “Why do you think the brain is a quantum phenomenon? Direct involvement of consciousness in wave-function collapse is not mainstream view, & I’m very sceptical of any role of coherence in mental phenomenon.”

What I wrote was: “a number of scientists believe that the problem is not so much that people are being irrational; it is just that they are basing their decisions, not on classical logic, but on quantum logic. After all, quantum systems, such as us, are intrinsically uncertain and affected by history and context.” [As an example, see: Wang, Z., Solloway, T., S., M., R., & Busemeyer, J. R. (2014). Context effects produced by question orders reveal quantum nature of human judgments. Proceedings of the National Academy of Sciences, 111(26), 9431-9436.] Note that the fact that a system shows quantum properties does not mean it can be reduced to quantum mechanics. I don’t claim that consciousness is the product of quantum coherence, though it may well be. See for example: Atmanspacher, Harald and Thomas Filk (2014) “Non-Commutative Operations in Consciousness Studies,” Journal of Consciousness Studies.

Why is it helpful to compare the Scholes-Black equation to the Schrodinger equation? It’s a diffusion equation. I understand the math correspondence between the diffusion equation and the Schrodinger equation – it’s very useful in my own field as a formal device – but it involves imaginary time which seems unphysical here. In any case the Scholes-Black equation isn’t actually accurate as a representation of markets, as a diffusion equation doesn’t describe a random walk with step sizes whose variance is undefined (a Levy flight).”

This refers to the section: “It turned out that many of the formulas regularly used by ‘quants’ to value derivatives such as options (the right to buy or sell a security for a set price at a future date) could be restated as quantum effects. The Black-Scholes equation, for example, can be expressed as a version of the Schrödinger wave equation from quantum physics.” I am not claiming that this is particularly useful. My book The Money Formula (written with quant Paul Wilmott) discusses how the Black-Scholes equation and others have been abused in finance. Such equations were influenced in large part by quantum physics and the nuclear program, but only took part of the message (randomness). The quantum finance approach can address some of these shortcomings, by relaxing assumptions such as high liquidity, efficiency, etc.

“But why would you think a Schrodinger equation would help us understand economics better anyway? It’s a deterministic, linear equation of exactly the same class that you criticise economics for relying on.”

Not sure which part of the text this refers to, and I am not making exactly this claim. The main advantage of the quantum approach in areas such as decision making is that it allows us to consider effects such as context and history. Interesting that this was argued back in 1978 by Qadir, before behavioural economics was invented. Qadir, A. (1978). Quantum Economics. Pakistan Economic and Social Review, 16(3/4), 117–126.

“You compare money both to an observable – which has an uncertainty relationship with a conjugate variable (which is?) & also with a particle, so it has wave-particle duality. Isn’t this confusing an object with a property of the object?”

I define money objects to be transferable entities, created by a trusted authority, which have the special property of a defined monetary value, specified by a number and a currency unit (see The Evolution of Money, and this paper). They therefore combine the mental idea of a numerical quantity of money – the virtual wave attribute – with the physical idea of an object that can be possessed or transferred – the real particle attribute. Money objects are unique in that they have a defined value, so there is no chance of e.g. interference effects (a five-dollar bill doesn’t interfere with a ten-dollar bill in your wallet). However money objects are used to price goods through transactions in markets, where such effects can occur. In quantum finance, the conjugate variables for something like a stock are price and momentum. And one of the main findings of quantum cognition is that many behavioural economics effects can be explained in terms of interference. See e.g. Yukalov, V. I., & Sornette, D. (2015). Preference reversal in quantum decision theory. Frontiers in Psychology, 6, 1-7.

“I agree with you that economics needs to put more thought into understanding what kind of things money and value are & agree that money’s trying to do more than a simple scalar variable can manage. But it seems to me that invoking quantum mechanics doesn’t bring much more to the problem than a bunch of rather forced analogies.”

The piece does not evoke forced analogies,  it is saying that the money system is a quantum system in its own right, with its own versions of duality, indeterminacy, entanglement, and so on. This is not the same as saying that it is identical to quantum physics or reduces to it.

“E.g. quantum entanglement means something really very precise that isn’t at all the same as saying that people are connected, or even that one persons credit is someone else’s debt.”

To quote my textbook (Rae), “the word ‘entanglement’ refers to a quantum state of two or more variables, where the probabilities of the outcome of measurements on one of them depend on the state of the other – even though there is no interaction between them.” The classic example is of two entangled photons A and B, where a result of positive spin measured along a certain axis for A implies that a later measurement of B “can now yield only a negative result.” Suppose now that person A has a loan from person B. From the viewpoint of quantum decision theory (or just a mathematical model), we can view A’s decision to default as a measurement process similar to the measurement of a particle’s spin; and this decision changes the status of the loan instantaneously – it can only yield a negative result – as B will find if they try to get their money back. Obviously it is hard to think how one could perform something like a Bell’s test (designed to tease out relationships between entangled particles) on a loan agreement, since such tests require measurements along different spin axes, but that doesn’t mean entanglement does not occur.

“So I agree with you that there’s lots to be done in economics & it should learn from physics, but I think (as has already begun) the place to look is in stat mech (including complexity & network theory) rather than qm.”

I have been advocating for a complexity approach in several books (Economyths, Truth or Beauty, etc.), but I see the quantum approach as backing up that claim.The point is not that economists should try to build elaborate quantum models of the economy – indeed, the neoclassical emphasis on microfoundations is misplaced. Instead, prices are best seen as emergent properties (see this paper). At the same time, the quantum effects of money can scale up and affect the economy as a whole. An example is the quadrillion dollars worth of derivatives which have been strangely absent from mainstream macroeoconomic models – now that is confused and misleading.

Update: response to more twitter comments.

Economist David Harbord: “This bit of silliness by @d_orrell should be enough to keep @Noahpinion wound up for a day or two …”

Niels Bohr asked of one physics theory, “The question is whether it is crazy enough to be have a chance of being correct.” The economics version is that this theory might be silly – but is it silly enough?

“I recall someone showing up at the LSE when I was a graduate student claiming that the problem with economic theory was the assumption Newtonian time & space, hence we needed an Einsteinian revolution in economics! Might be worth checking up on progress in that research program.”

Over a century ago some people showed up claiming that economics should be based on Newtonian mechanics. We all know how that research program is going.

“Both suggestions focus on phenomena at the wrong scale for modelling economic activity. If you can produce a model in which quantum effects matter & make predictions that ‘Newtonian’ economics cannot (lots of scope there!), then I’ll admit you are on to something.”

I’m not saying economics reduces to quantum physics – I am saying that money has its own quantum properties, which do scale up. But read the book when it comes out and judge for yourself. For my thoughts on prediction, see this recent article for Newsweek Japan.

Thread begun by science communicator Natalie Wolchover from Quanta:

What a load of hogwash.”

Like traditional economics then – with the nice difference that it doesn’t act as the PR wing for an out-of-control financial sector.

Further comments by various people on the same thread:

“I thought these guys were starting to get passed the physics envy.”

I actually trained in math and physics, so perhaps this should be economics envy. In my previous books such as Economyths I have done as much as most people to argue against the idea that economics can be simply transposed from physics. However metaphor is intrinsic to our thought processes, and neoclassical economics has long been replete with metaphors from Victorian mechanics – one of its founders Vilfredo Pareto for example said that “pure economics is a sort of mechanics or akin to mechanics” – so perhaps it is time to expand our mental toolbox. After all, it isn’t just quantum mechanics which has been “misused and abused” (to quote Sean Carroll). Also, while I did study quantum mechanics, and use it in my work (my early career was spent designing superconducting magnets which rely on quantum processes for their function), my intention is not to further mathematicise economics – quite the opposite. The core ideas of the theory proposed are very simple.

“Can hardly wait for the forthcoming quantum astrology piece.” “Or auto repair done by quantum mechanics.” “I would be happy to have dollars tunnel from pockets of rich folks to mine.” “That’s about two steps away from Deepity Chakra.” “I think he means a paradigm shift.” “To quote physicist Wolfgang Pauli, this is not even wrong.”

Not even funny … Physicists have been very careful to put up a lot of filters around quantum ideas, which is understandable, but is also one reason social scientists are stuck in an oddly mechanistic view of the world. So we need more discussion between these areas.

For more comments and responses, see the comments thread in the article.



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