In certain systems, the output of a mechanism (or the effect) can be used (or is desirable) as the input of the same mechanism. This results in the rapid propagation/acceleration of the system, if left unattended or unregulated.
- A classic example is feedback from a microphone and speaker. Sound passing into the microphone is then amplified and sent out of the speaker, which enters the microphone once more. This would continue until the speakers blow themselves out, or more commonly, an internal device prevents any further audio input (which in itself is a form of regulation).

University of Michigan - Ann Arbor

University of Illinois at Urbana-Champaign

Loops that amplify, reinforce, self-multiply, or snowball a stock level. They can lead to positive cycles of increasing stock or negative cycles of decreasing stock.

Runaway Loops - Reinforcing Feedback

Daniel Rigney. (2010). The Matthew Effect : How Advantage Begets Further Advantage. Columbia University Press.

The Matthew Effect by Daniel Rigney

Positive Feedback Loops

"In economics, a poverty trap or cycle of poverty are cause by self-reinforcing mechanisms that cause poverty, once it exists, to persist unless there is outside intervention." 

Cycle of Poverty / Poverty Trap

The Matthew Effect describes the phenomenon that in societies the rich tend to get richer and the strong even more powerful. The concept today describes the general pattern of self-reinforcing inequality related to economic wealth, political power, prestige, knowledge or in fact any other scarce or valued resource. 

The Matthew Effect

Narratives spun by past explanations of events set us up for further success or failure. Self-fulfilling prophecies occur when we act on our previous attributions (explanations) of events. I.e., "I failed the last test so I am stupid and it isn't worth studying for the next test because I'll fail anyways"; fails next test; "See I told you I would fail."

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