Feedback (positive)

When I was a kid, my cousin had a tape-recorder just like this one – it had a microphone with a yellow sponge. Putting the microphone in a nearby (empty) pot produced this wonderful echoey noise that grew to a delightful – to my ears – whining whistle.

The whine grew slowly at first, but the louder it got, the faster it grew before maxing out, ending when you took mic back out (you could hold it constant by holding the mic just at the mouth of the pot) or when an irritated parent had had enough.

Here’s a diagram of what’s happening:

(wikipedia)

There a lot of ways this happens in the rest of life too, for good and bad:

  • The virtuous circle of a team doing better work, getting better customers, who ask them to do better work, leading to more opportunities…
  • Technological innovation
  • Investment, reinvestment and compound interest
  • Population growth
  • Environmental destruction
  • Cattle stampedes
  • Bad sleep, leading to bad decisions and more work, leading to worse sleep…

Feedback loops come with a caveat:

Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillationschaotic behavior or other divergences from equilibrium. System parameters will typically accelerate towards extreme values, which may damage or destroy the system, or may end with the system latched into a new stable state.

Wikipedia

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