Feedback loops
When a system's output feeds back into its input, small nudges can snowball. Crowds, prices, volatility and even deployed models run on loops like this — and they tend to stay quiet until they don't.
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Pattern Essays
The Feedback Loop
The mechanism: output becomes input, so each change makes the next one larger — or damps it away.
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Market Psychology
Herd Behavior
Buying because others are buying. Rising prices are the reason for the next rise.
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Market Psychology
Information Cascades
Why a crowd can be rational and still wrong: each person follows the ones before, and an early signal tips everyone.
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Market Psychology
Market Sentiment Cycle
The loop running both ways — euphoria feeding on gains, panic feeding on losses.
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Timeseries Engineering
GARCH
Feedback in the noise itself: turbulent days make more turbulent days likely, so volatility clusters.
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MLOps & Production ML
Drift Detection in Production
Deployed models live in a loop too. When the world shifts — sometimes because of the model's own decisions — yesterday's patterns stop holding.
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Pattern Essays
The Threshold
Loops can build quietly for a long time, then cross a threshold and change the system all at once.
Look for the arrow from output back to input. Where it exists, extrapolating from calm periods understates what can happen next.
Add up enough small, independent nudges and the same curve appears — in sample averages, in price bands, in risk models. Follow it across four fields, then see where it quietly stops being true.
Extreme results tend to be followed by less extreme ones. It looks like a force pulling things back; it is arithmetic. Watch the same idea turn into trading signals, portfolio rules and model penalties.
Every field has the same problem: real structure mixed with randomness. These stops are the tools for pulling them apart — and for checking you have not invented a pattern that was never there.
The data you can see is often the data that survived. Patterns found in it can be an artefact of what went missing. These stops show how the trap works, and the habits that keep you out of it.
Recent direction tends to carry on, for a while. The same idea speeds up neural-network training, drives a family of trading indicators, shapes how traders add to winners and fuels the crowd. Follow it, and see where it stops paying.
Many systems change all at once when a line is crossed. A neuron fires, a classifier says yes, a language model drops its unlikely words, a price breaks out, a stop-loss sells. Each stop is a threshold, and each has to answer the same question: where to draw the line.