Subject: Feedback Loops

Posted by John Sterman on 2/9/2006
In Reply To:Feedback Loops Posted by Levin, Jeffrey S. on 2/9/2006

Message:

There are literally thousands of feedback loops involved in the physical growth of a person (up or out). Your level of hunger affects behavioral responses including choosing when, what, and how much to eat, which feeds back to your hunger, to your weight, to your psychological state, all of which then feed back (literally) to your next decisions to eat.

You may not perceive any connection between your consumption of resources like food, water, sunlight, and oxygen and the sources or supplies of these inputs, but the feedback is there. One person's consumption activities don't make a noticeable difference to the ecosystems of the planet, but collectively the 6.3 billion people certainly do; indeed, the feedbacks from individual activities to the ecosystem are now so many and so large that human activity has already transformed the planet and changed the climate. The best scientific estimates are that human activity consumes about 40% of net primary production (the total amount of sunlight and other nutrients converted by photosynthesis into biomass worldwide, including the oceans).

Feedback need not involve purposeful action by a conscious agent.
The many physiological feedbacks without which you could not survive (temperature regulation by sweating or shivering, insulin secretion to regulate glucose concentrations, the contraction of the iris in response to bright light, etc. etc. etc.) operate without any conscious volition. Further, many feedbacks are not self-regulating (negative), but are self-reinforcing (positive), so there isn't even an implicit goal or control. For example, people with severe cases of influenza are often too sick to eat and hydrate, which causes them to become even weaker, which further limits their ability to take nourishment. In severe cases mortality results not from any direct physical damage caused by the influenza virus but from the positive feedback. Here feedback determines what happens without any goal seeking, implicit or conscious.

Everything that changes through time involves feedback, whether that change is intended or unintended, purposeful or not, involves human agency or natural processes.

Of course this does not mean that tools and perspectives that don't make feedback central are wrong or unimportant or not useful.
Different purposes call for different models. Using a framework that doesn't explicitly account for feedback processes doesn't mean those feedbacks aren't there. And many of the problems we face individually and collectively can be traced to our failure to recognize the many feedbacks created by our interactions with the environment in which we are embedded.

John Sterman