Friday, September 5, 2014

Feynman gets one wrong?

Imagine how much harder physics would be if electrons had feelings!
 – Richard Feynman, speaking at a Caltech graduation ceremony.

I found this quote in "WARNING: Physics Envy May Be Hazardous To Your Wealth!" by Andrew Lo and Mark Mueller. I took it as a challenge. Let's switch from electrons to molecules for first brush analysis using statistical mechanics.

There are approximately 6 x 10^23 molecules in 18 grams of water. Wikipedia lists approximately 70 human emotions substantial enough to receive their own listing in the side bar. Call it 100 as an order of magnitude estimate and say the emotion of a given molecule represents a vector in a 100 dimensional vector space. Unless the molecules were highly correlated in their emotions, there would still be 6 x 10^21 ± 8 x 10^10 molecules of each emotion (a variance of 0.000000001%) and the average emotion would be fairly neutral to a high degree of certainty [1].

Now, sure, that error represents a ten-fold increase in the expected variance of ensemble averages of emotionless water molecules. But we really don't measure many thermodynamic quantities to that level of accuracy (except maybe the cosmic microwave background radiation). Essentially, physics would be the same if molecules had feelings unless they also had ways to coordinate their emotions -- and a society that has correlated emotions usually doesn't have functioning markets because they're at war or there's an economic depression [2].

This is why I am skeptical that including human behavior in macroeconomics would be fruitful.


[1] Applying this calculation to e.g. the US labor force (130 million people) results in an error of 0.09% -- a tenfold increase over the emotionless error of 0.009%.

[2] This raises an interesting question: Do correlated emotions ruin the ability of markets to function?

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