This glossary contains a vocabulary used by CPER concerning the overall site, regarding: meaning of scientific words, useful definitions, short explanations of some concepts, and references to reliable external sources of information on the Internet or on paper.
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Feedback occurs when outputs of a system are "fed back" as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to "feed back" into itself. The notion of 'cause-and-effect' has to be handled carefully when applied to feedback systems: Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole. In this context, the term "feedback" has also been used as an abbreviation for:
Positive - Negative
The terms positive and negative feedback are defined in different ways within different disciplines:
Fields of Application
In biological systems such as organisms, ecosystems, or the
biosphere, most parameters must stay under control within a
narrow range around a certain optimal level under certain
Biological systems contain many types of regulatory circuits,
both positive and negative. As in other contexts, positive and
negative do not imply that the feedback causes good or bad
effects. A negative feedback loop is one that tends to slow down
a process, whereas the positive feedback loop tends to accelerate
Feedback is also central to the operations of genes and gene regulatory networks. Repressor (see Lac repressor) and activator proteins are used to create genetic operons, which were identified by Francois Jacob and Jacques Monod in 1961 as feedback loops. These feedback loops may be positive (as in the case of the coupling between a sugar molecule and the proteins that import sugar into a bacterial cell), or negative (as is often the case in metabolic consumption).
On a larger scale, feedback can have a stabilizing effect on
animal populations even when profoundly affected by external
changes, although time lags in feedback response can give rise to
In psychology, the body receives a stimulus from the environment or internally that causes the release of hormones. Release of hormones then may cause more of those hormones to be released, causing a positive feedback loop. This cycle is also found in certain behaviour. For example, "shame loops" occur in people who blush easily. When they realize that they are blushing, they become even more embarrassed, which leads to further blushing, and so on.