Causation in Complex Systems

by Russ Roberts on January 10, 2012

in Complexity & Emergence

Jonah Lehrer explains the challenge of determining causation in complex systems (HT: John Papola). The article focuses on medicine but it could have been written about macroeconomics. As Ed Leamer says, we are story-telling pattern-seeking animals.

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Bob January 10, 2012 at 5:28 pm

Before retirement, I spent several years working with the Marine Corps, using computers to model battlefield dynamics. ALL digital models contain shortcuts, whether models of climate, pollutants, sociology, economics, war, medicine. Modifying even one input, even by a tiny amount, changes the entire model’s behavior. The Marine Corps was not necessarily trying to devise the best computer model, but they were really trying to understand the effect of those tiny tweaks. History and experience demonstrate that small, often unregarded changes to the “input” of a system, can cause huge differences in the “output” of the system, including, of course, those famous “unintended consequences”.

Anyone who says they have the perfect model of an economy, ecology, etc, will soon find out that they are very wrong, and the “system” will bite them with often disastrous results.

Greg Webb January 11, 2012 at 5:53 pm

Excellent! And exactly right! That is wisdom, which often escapes the young, inexperienced, and overly egotistical people who belief that they, and only they, can fix any problem and save the world from itself. We need more wisdom, not more education.

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