What is complexity?

By  via http://www.farnamstreetblog.com/   Article

“While it seems more and more common these days, it’s important to determine when you’re operating in complexity. Complexity means that little things can have a big effect and big things can have no impact. Complexity also renders some of the way we think about problems as useless, at best.

In The Black Swan: The Impact of the Highly Improbable Fragility, Nassim Taleb writes:

I will simplify here with a functional definition of complexity—among many more complete ones. A complex domain is characterized by the following: there is a great degree of interdependence between its elements, both temporal (a variable depends on its past changes), horizontal (variables depend on one another), and diagonal (variable A depends on the past history of variable B). As a result of this interdependence, mechanisms are subjected to positive, reinforcing feedback loops, which cause “fat tails.” That is, they prevent the working of the Central Limit Theorem that, as we saw in Chapter 15 , establishes Mediocristan thin tails under summation and aggregation of elements and causes “convergence to the Gaussian.” In lay terms, moves are exacerbated over time instead of being dampened by counterbalancing forces. Finally, we have nonlinearities that accentuate the fat tails.

So, complexity implies Extremistan. (The opposite is not necessarily true.”

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