The Drunkard’s Walk, The Butterfly Effect and The Black Swan

drunkards walk

The “drunkard’s walk” refers to the Brownian motion, the seemingly random movement of particles suspended in a fluid. The original thought was that you might be able to calculate the movement by measuring and calculating the interaction. It proved impossible. There are too many factors and too many interactions.

Small changes in a system can dramatically affect the outcome. This is the butterfly effect. The origin cam from a meteorologist who was using a computer model to rerun a weather prediction and one of the numbers he used was shortened from six decimal points to three decimal points. The result was a completely different weather scenario. It’s not that a butterfly can cause the problem. It’s that a seemingly inconsequential random event can lead to a big change in an outcome.

Leonard Mlodinow addressed this topic in The Drunkard’s Walk: How Randomness Rules Our Lives. (I mentioned the book previously in Criticism and Praise.) There is much more randomness in our lives than we give credit.

We poorly understand the effect of randomness.

He explores his concepts using the backdrop of Pearl Harbor. In hindsight there were many signs pointing to the eventual attack. “In any complex string of events in which each event unfolds with some element of uncertainty, there is a fundamental asymmetry between past and future.” It’s nearly impossible to predict before the fact, but relatively easy to understand afterward. We have seen the same 20/20 hindsight with the 9/11 attacks.

That’s why it is easy to explain why the weather happened three days ago, but have trouble getting the weather forecast right three days into the future.

Mlodinow never mentions it, but for me the next step is the theory of the Black Swan. How do you end up with high-impact, hard-to-predict, and rare events that are beyond the realm of normal expectations?

Combining the Black Swan with the Drunkard’s Walk and the Butterfly Effect, you see that a combination of small events can lead to an over-sized outcome. We get used to being able to calculate and measure so many things. There will always be factors that we miss, or overweight or underweight.

Not to be depressing. The Drunkard’s Walk leaves you feeling in less control than when you started. But there is a factor you can control: the number of chances that you take. “Even a coin weighted toward failure will sometimes land on success.” Keep flipping the coin.

The Drunkard’s Walk is worth reading if you deal with risk.

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