![]() Such feedback systems and network effects and their failure modes are often the subject of systems theory. The Fukushima explosions were the result of a cascade failure of negative feedback systems that were designed to prevent the positive feedback of a nuclear reaction from running away into nuclear meltdown. Positive feedback ( exacerbating feedback, self-reinforcing feedback) is a process that amplifies the effects of a small disturbance in a feedback loop.Įxamples include a trickle overtopping an earthen dam, which washes away a bit of soil, letting more water overtop the dam, which carves a trench by carrying yet more soil away, and ultimately leads - sometimes in mere minutes - to the total collapse of the dam or a nuclear chain reaction in which a flying neutron in a chunk of fissile material collides with and splits an atomic nucleus causing the release of more neutrons, which then go on to collide with yet more nuclei releasing yet more neutrons, and so on.Ĭascade failure is a more general example of positive feedback, in which failures accumulate and amplify each other like more and more domino toppling or a house of cards collapsing (both are examples of positive feedback). The above photo is of the UK Northern Rock 2007 bank run. ![]() In sociology a network effect can quickly create the positive feedback of a bank run. Alarm or panic can sometimes be spread by positive feedback among a herd of animals to cause a stampede. Self-reinforcing effect Causal loop diagram that depicts the causes of a stampede as a positive feedback loop.
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