FEEDBACK
| Collection | International Encyclopedia of Systems and Cybernetics |
|---|---|
| Year | 2004 |
| Vol. (num.) | 2(1) |
| ID | ◀ 1251 ▶ |
| Object type | General information, Methodology or model |
1) “A unilateral power amplifier, with a fraction of the output of the amplifier substracted from or added to the input of the amplifier” (M.D. RUBIN, 1968, p.9).
2) “The use of part of the output of a regulated system to compare with the standard set for its program and produce appropriate change of input” (J.Z. YOUNG, 1978, p.292).
The first definition is an engineer's one corresponding to a host of practical devices. It can be generalized by substituting “effect” for “power”.
From this definition it is already obvious that any feedback device will have either positive (increasing) or negative (decreasing) effects on the process.
J.Z. YOUNG's definition explains what feedbacks do.
He adds that :“Positive feedback increases the input and negative feedback decreases the input”, something whose disequilibrating consequences on the system are portentous when sustained feedback of one or the other kind are not adequately compensated.
The Italian epistemologist V. TONINI states: “Feedback is the dominant condition for self-regulation, adaptation and automation; this is sufficient within the limits of a well defined control of some variable. Feedback is a typically analogic and conservative principle. (However) nowadays this certainly very important principle seems insufficient for the cybernetic regulation of complex organisms” (1971, p.288-9).
What is needed in such cases is a compensating and appropriate alternance of positive and negative feedback, in order to secure homeostasis.
The following definition, by G. PASK is more typically cybernetic and, thus, general: “Return of a signal, indicating the result of an action., in order to determine further action” (1961, p.114).
R.L. ACKOFF and F.E. EMERY introduce an information as well as psychological connotation in their own definition: “Information received by the sender of a message about the receipt of, or response to his message” (1972, p.187).
R. VALLÉE points out that H. SCHMIDT (1894-1968) had already introduced during the thirties an Allgemeine Regelkreislehre, i.e. a “General feedback loops science” (1995, p.13), being thus another forgotten precusor of cybernetics.