Positive (Self-reinforcing) Feedback Loops

Positive feedback loops are not inherently ‘positive’ in the sense of moral or value goodness. Perhaps we should call them ‘self-reinforcing’ loops or ‘run amok’ loops instead. Here’s an easy definition for positive feedback loops: the more of something you have, the more of something you get. Positive feedback loops do not self-correct.

Heat makes the ice caps melt, which means more ocean water traps heat, which means more ice caps melt.

Wealthy people have money to invest, so they earn interest and get even richer. Poor people are often paying interest on debt, so they lose a portion of their income instead of saving it, which keeps them poor.

Person A hears a rumour and passes it on to Person B.
Person B tells Person C.
Person C tells Person A.
“Ah hah!” explains Person A, “I can’t believe you heard that, too! It must be true!” Having received positive feedback from the system, Person A is reenergized to communicate the rumour more widely, thus influencing an even greater scope of the network. (In social systems like ours, multiple, conflicting rumours circulate simultaneously. Each rumour reinforces its believers and infuriates its skeptics. When rumours clash, they force people to respond by accepting, rejecting, adapting, synthesizing, or amalgamating rumours. This, in turn, gives rise to even more rumours.)

A positive feedback loop is like a ball rolling down a hill. A simple little nudge is all it takes for the process to gain momentum, and with enough momentum the ball becomes unstoppable. Eventually, a positive feedback loop will lead to collapse: an uncheck or unregulated positive feedback loop is like an epidemic that will sooner or later run out of victims to infect. If everything has not already collapsed, it is because a negative (self-correcting) feedback loop has emerged.


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This page a subsection of 'Leverage Points' in the System Thinker Notebook manuscript.
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