Where the outputs or past results of a process or phenomenon act as inputs to its future behaviour. These effects can be positive or negative. Snowflake growth is an example of positive feedback where any small growth grows further. In contrast, a negative feedback process smooths out changes, for example any protuberances on a pebble tend to be eroded more as it is turned over on the seashore, so that the pebble becomes rounded over time. Feedback effects may cause {{nonlinearity}, because some initial change can make huge differences.
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