Overview

Feedback Loops are the engines of change and stability. They are the reason things grow (compound interest) and the reason things stay the same (body temperature).

Core Idea

The core idea is circularity. A causes B, and B causes A.

  • Reinforcing (Positive) Feedback: A produces more B, which produces more A. (Explosion, Growth).
  • Balancing (Negative) Feedback: A produces B, which reduces A. (Stability, Goal-seeking).

Formal Definition

A situation where some of the output of a system returns to the input.

Intuition

  • Microphone Squeal (Positive Feedback): Sound goes in mic -> Amp -> Speaker -> Mic -> Louder Sound. Loop continues until SCREECH.
  • Toilet Flush (Negative Feedback): Water level drops -> Float drops -> Valve opens -> Water fills -> Float rises -> Valve closes.

Examples

  • Compound Interest (Positive): Money earns interest. Interest becomes principal. Earns more interest.
  • Predator-Prey (Balancing): More rabbits -> More wolves -> Fewer rabbits -> Fewer wolves -> More rabbits.
  • Viral Content (Positive): More likes -> Shown to more people -> More likes.

Common Misconceptions

  • Misconception: Positive feedback is “good” and negative feedback is “bad.”
    • Correction: “Positive” means adding (amplifying). “Negative” means subtracting (stabilizing). Positive feedback can be bad (cancer, panic). Negative feedback can be good (thermostat).
  • Misconception: Loops happen instantly.
    • Correction: There are often Delays. A delay in a balancing loop causes oscillation (like a shower that’s too hot, then too cold).

Applications

  • Climate Change: Melting ice reflects less sun -> Warmer -> More melting (Positive Feedback).
  • Business: Viral loops for growth.
  • Engineering: Control systems.

Criticism and Limitations

  • Runaway Loops: Positive feedback eventually hits a limit (collapse), or the system destroys itself.

Further Reading

  • Thinking in Systems by Donella Meadows