Feedback Loops

A feedback loop forms when the level of a stock influences the flows that change that same stock, so the system acts on itself. There are two kinds: reinforcing loops that amplify and balancing loops that stabilize.

Why it Matters

Feedback is what makes a system generate its own behavior over time. Growth, stability, oscillation, and collapse come from the loop structure, not from external pushes, so understanding the loops lets you anticipate the dynamics.

Signals

• An output that loops back to affect its own input.
• Behavior that continues or changes on its own without a new external cause.
• A quantity whose current size sets how fast it grows or shrinks.

Benefits

Shifts attention from isolated events to the structure that generates them, and lets you predict how a system will behave from the loops it contains rather than from the latest event.

Risks

Seeing only one loop when several interact and offset each other; assuming a system is driven from outside when it is actually driven by its own internal loops.

Tensions

Reinforcing loops drive growth but also drive collapse; balancing loops create stability but also resist desired change. A system is usually a tug of war between loops, and which one dominates can shift over time.

Examples

Interest compounding on a balance is a reinforcing loop. A thermostat holding a room near a set temperature is a balancing loop.