Tuesday, July 23, 2019

Cause and Effect in Complex Systems - Think in Terms of Reinforcement Cycles

In the last post, I wrote about the virtuous cycle of labor gradually getting more valuable, driving the development of machines to extend that value, which in turn makes it more valuable still. This is an example of a potentially useful trick in reasoning about complex systems that avoids a cognitive pitfall.

In a complicated system in equilibrium, it is unlikely that a single element of many in the system could be responsible for a lasting perturbation or evolution to a new equilibrium. That is, reasoning about single-causes unidirectionally affecting the rest of the system is probably not a good way to improve our understanding. It's not like kicking a ball - foot causes ball to move, end of story - which is the way our brains seem to have developed to understand events on the order of a few seconds in the mesoscale world. (Notice even there that the ball moves once, stops, and the phenomenon is over.)

Mutually reinforcing sets of elements within the system are more likely to produce a lasting perturbation, that is, move the system to a new equilibrium. Looking for such reinforcement cycles can get us out of unproductive chicken-and-egg reasoning. Applying the idea to this case, it becomes evident that asking "Was it labor getting cheaper that caused the industrial revolution? Or the other way around?" is simplistic and unlikely to provide a clear and useful answer. It's better to ask, "What are the economic and social elements that reinforced each other in such a way as to produce the industrial revolution?" - along with other elements such as aspects of British culture at that time.

Another example would be the question: "Was increased use of tools and manual dexterity in early human ancestors a result of these ancestors favoring bipedal locomotion? Or the other way around?" They likely reinforced each other, along with other elements; i.e., increased adaptation to the savannah favoring bipedal locomotion to see further and tool use favoring survival in a drier, more open, less calorie-dense environment - et cetera.

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