Feedback

Definition (Norbert Wiener)
Definition (F. de P. Hanika)
Classification (Hans Ozbekhan)
Classification (George Chadwick)
Features (Andreas Faludi)
Limitations (W. Ross Ashby)
Related Concept : feedforward (Herbert A. Simon)
Related concept : homeostasis (F. de P. Hanika)

Definition

[1954] Norbert Wiener, The Human Use of Human Beings. Cybernetics and Society, Eyre and Spottiswoode, London
“Feedback is a method of controlling a system by reinserting into it the results of its past performance.” (p. 61)
“... by feedback - or, as it is often called, a servo-mechanism - is meant a communications network that produces action in response to an input of information and includes the results of its own action in the new information by which it modifies its subsequent behaviour.” (p. 88)

[1972, First edition 1965] F. de P. Hanika, New Thinking in Management, Heinemann, London
“In essence, feed-back represents any arrangement whereby the output from a process or situation is measured and compared with a pre-set standard, and corrective action is initiated if output deviates from that standard.” (p. 11)

Classification

[1968] Hans Ozbekhan in Eric Jantsch ed., Perspectives of Planning, OECD
“1. Purposeful active behaviour may be subdivided into two classes: ‘feed-back’ (or teleological) and ‘non-feed-back’ (or non-teleological)
2. Feed-back may be either positive or negative, and it is in the latter sense that feed-back acts as a 'control'. The behaviour of an object can be controlled by the amount of its deviation from a particular goal at a particular time. When such a ‘margin of error’ occurs, the feed-back signals from the goal become negative; they inhibit outputs which would overshoot the goal.
3. These signals from the goal guide behaviour. Feed-back keeps purposeful behaviour on course by reacting to the amount of its deviation from a particular goal. All purposeful behaviour requires negative feed-back at some time or other if it is to attain its goal.
4. Negative feedback is restrictive, positive feed-back augments. (This is sometimes referred as the ‘amplification effect’).” (p. 110)

[1971] George Chadwick, A Systems View of Planning, Pergamon Press, Oxford
- Negative Feedback. “Deviation-controlling feedback is an error-correcting mechanism, and for this reason is called negative feedback.”
- Positive Feedback. “Deviation-amplifying or positive feedback.” “... the expansion of the more highly organized parts of an ecosystem at the expense of the less organized parts (morphogenesis) is due to positive feedback.” (p. 58)

Features

[ 1976, First published 1973] Andreas Faludi, Planning Theory, Pergamon Press, Oxford
“The components of a controlled feedback system are:
- the receptor gauging the existing state of the environment and the effect of actions on it (feedback);
- the selector choosing between alternative responses on the basis of information received from the detector;
- the effector producing changes in the environment on the basis of instructions from the selector.” (p. 60)

Limitations

[1956] W. Ross Ashby, An Introduction to Cybernetics. Chapman & Hall, London
“... the concept of feedback ... becomes artificial and of little use when the interconnections between the parts become more complex.” “... when the parts rise to even as few as four, if everyone affects the other three, then twenty circuits can be traced through them; and knowing the properties of all the twenty circuits does not give complete information about the system. Such complex systems cannot be treated as an interlaced set of more or less independent feedback circuits, but only as a whole. For understanding the general principles of dynamic systems, therefore, the concept of feedback is inadequate in itself.” (p. 54)

Related concept : Feedforward

[1988, First edition 1969] Herbert A. Simon, The Sciences of the Artificial, M.I.T. Press, Cambridge Massachusetts
“In general a system can be steered more accurately if it employs feedforward, based on predictions of the future, in combination with feedback, to correct the errors of the past.” (p. 44)
“Feedforward in a control system can have unfortunate destabilizing effects, for the attempt of the system to look ahead may cause it to become overreactive and go into unstable oscillation.” (p. 44)

Rekated concept : Homeostasis

[1972, First edition 1965] F. de P. Hanika, New Thinking in Management, Heinemann, London
“This particular form of feedback to maintain physiological balance (e.g. the equilibrium between body-heat and outside temperature) has long been familiar to biologists, who speak of it as ‘homeostasis’.” (p. 13)

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