Defined by Norbert Wiener in 1948 as the science of communication and control in the animal and the machine, cybernetics has been more or less broadly interpreted. In the U.S.S.R. and, to a lesser extent, in Europe, cybernetics adumbrates large parts of control theory, automaton theory, information processing and computation, as well as operational research and the modeling of brains and organisms. In the United States, on the other hand, cybernetics was used only to designate the narrower field of information feedback systems, controllers or regulators, treated principally from an engineering point of view. The tendency to adopt a restricted interpretation for the term has been largely reversed but, as a result of its existence for a number of years, much of the American literature on cybernetics (in the general sense) appears in connection with the disciplines to which it was applied, or under specialized headings. Among the most important of these are: General Systems Theory, Bionics (q.v.; Biological Cybernetics, using the organizational principles of living systems in the design of artifacts), the theory of "Self Organizing" or evolutionary systems and "Artificial Intelligence." The last area includes the study of computer programs that are guaranteed to solve problems (namely algorithms) and "heuristic" programs that make "intelligent" (and often very economic) shortcuts in problem solving but that are not necessarily guaranteed to work on all occasions.
A broad definition is hazy, but the trouble with a narrow one is that it obscures the essential interdisciplinary character of cybernetics. Systems of communication and control are ubiquitous in nature, in psychology, and in engineering. Their cybernetic formalization unifies concepts from many fields. Since one important function of cybernetics is to unify diverse disciplines it is not surprising that there are rather few fulltime cybernetic theoreticians, but a large number of investigators who do cybernetics part of the time, or who apply its principles in their work.
Basic Principles.-Cybernetics is primarily the science of constructing, manipulating, and applying cybernetic models which represent the organization of physical entities (such as animals, brains, societies, industrial plants, and machines) or symbolic entities (such as information systems, languages, and cognitive processes).
A paradigmatic organization, and the building block from which most cybernetic models are fabricated, is a "goal-directed system or "control system." Such a system contains the following four - parts: (1) Sensor (S) : an abstractive process whereby the mediate state of the system's environment is described in terms of salient attributes or properties.(2) Goal (G) : the spefication of a particular state of the system called the goal - (3) Error Detection (E) : a method for determining the deviation, if any, between the goal state and the intermediate state -(4) Effector (E'): a set of operations whereby the system can act upon and modify certain features of the environment which are relevant to or correlated with the descriptive properties. These parts embody the following two rules: (a) a rule asserting well-defined procedure for discovering, which of the possible actions are likely to bring the immediate state nearer to the goal state, and (b) a rule whereby, given an instruction "Achieve Goal", the system acts upon its environment, guided by the deviation measure (or "difference signal") of the Error Detector (3), so that the goal state is approximated (the deviation is minimized). Generally, the system replies to this instruction: by a statement "G is achieved", or a statement "So much effort has been expended in pursuit of G, but without success."
In the simplest cases, all parts of this specification are constant -with the possible exception of the instruction cited in (b). If the instruction is also constant, the goal-directed system is called a homeostat (and continually seeks state G). In general, however, some or all aspects of the specification are variable.
Such an elementary device as a central heating controller forms to all of these requirements. Here (1) is identified - the thermometer of the thermostat that reads room temperature, (T). (2) with the desired room temperature, T', (3) compares T- and T' and establishes which is the higher, and (4) is the furnace; (a) is the simple negative feedback rule: "turn on if room temperature, T, is less than T', otherwise turn off", and (b) an instruction provided manually or by a timing apparatus. But these conditions are also satisfied by very complex industrial and vehicle controllers and by natural systems at all levels of complexity. On a philosophical plane, the formalization of systems entailing the circular flow of information has resolved many of the dilemmas once engendered by teleology and purposiveness.
Nor is the goal-directed system necessarily tangible. A game (a business game or any simulation in the sense of game theory; q.v.) is also of this type. Further, a goal-directed system may be part of a computer program or a symbolic and problem-solving process. Analogy completion is typical in this respect. Given the symbolic objects, A, B, and C, the system seeks the goal (of completing an analogy) by describing the relation of A to B and finding D (or modifying some existing D') so that the statement "A is to B as C is to D" is satisfied.
Cybernetic models are structures of mathematically related goal-directed systems, often combined with other elements such as logical operators and information storage media. The systems may be combined by coupling their variables (usually to yield a macro-system with properties in excess of those of its components). They can interact competitively (their goals remaining unchanged) or cooperatively, in which case, communication must take place in a suitable language to arrive at a compromise goal. A system with goal G, may also be sequentially connected to a system with goal G2 in the sense that attainment of G1 delivers an instruction to achieve G2 (In this case, G1 and G2 are called subgoals of the goal of the conjoint system.) Finally, they can be organized into a hierarchy, in which only the lowest-level systems act upon the environment or have goals that refer to it directly. The higher-level systems sense lower-level properties and organize the lower-level systems.
Hierarchical structures comprehend such processes as planning and learning. In planning, a higher-level system Z is instructed to achieve an abstract goal, G. It forms a plan insofar as it can recognize that G entails the subgoals G1, and G2 which are in the repertoire of the available lower-level systems and insofar as it organizes them in sequence to attain G. Learning can be viewed as the system-organizing response of Z to a problem which remains insolvable until Z, has modified the characteristics of the lower-level systems in its domain.
Applied Cybernetics.-Cybernetic models are applied prescriptively in design and descriptively as explanatory devices. Their prescriptive use savours of engineering. They are employed in the specification of controllers and regulators for industrial plants, navigation, and so on. The most interesting developments have occurred in the area of predictive, adaptive, and optimizing controllers, usually able to deal with randomly perturbed environments. On the other hand, cybernetic models are widely used in determining the proper relationship between a man and a machine, for example, in the design of vehicle-control systems. Another field of application is teaching and training. Here, training is literally interpreted as the control of a human learning process and insofar as an adequate model exists, the training instructor may be partially or wholly replaced by a suitable machine. In operational research, cybernetic models are used to specify stockholding schemes, process and assembly programming, and inventory control. They are also used in a normative fashion; for example the management of a business enterprise is often modeled as a game-like decision and control process.
Descriptive applications are legion. At a neurophysiological level, cybernetic models have been used to explain many aspects of the working of a brain. Five areas are of special importance: models for simplified neural networks, chiefly representing perceptual processes; statistical models for the complex oscillations and regulations of real neural activity; models relating algorithms or plans (cited earlier) to the conditioning process; models for the mechanisms responsible for maintaining and directing attention; and models for the detailed changes that occur at the synaptic junctions between neurons.
Outside the brain, cybernetic principles are widely used to elucidate the control of bodily functions (autonomic processes, hormone-mediated regulatory systems, muscular control, and so on). A surprisingly large amount of molecular biology and bio-chemistry also rests upon models depicting the organization of enzyme systems and the hierarchical control of enzyme synthesis. This type of explanation promises to have further utility in relating genetically coded instructions to the cellular economy. Cybernetic models have been used in embryology since the early 1950s, and some of the original schemes have now been formulated in a detailed mathematical fashion.
Within psychology, it is possible to explain several classes of behaviour and cognition in terms of hierarchies of control systems. The previously stated notions of planning and learning are pertinent to this field. At a macroscopic level, cybernetic ideas are applied to interpersonal interactions such as conversations, the communicative behaviour of small groups, and the homeostatic processes maintaining the status quo in social systems. Indeed, one of the first essays in this direction took place in the context of social anthropology where cybernetic ideas are becoming of greater importance. Somewhat similar developments have occurred in the animal domain; ethnologists use cybernetics freely, especially in dealing with population density control systems and the regulation of reproduction.
Pure Cybernetics.-Pure cybernetics has an axiomatic and a philosophical aspect. The axiomatic paradigm is to assume certain postulates about a system and to deduce the system properties (such as reproduction, differentiation, learning) that are consequences of these assumptions. The philosophical branch of the science is often concerned with theories; for example, the theory of simplification (how the complex properties of a real system can be reduced to manageable proportions without losing essential information) and the theory of commands. But it is also concerned with the issue of relevance as well as with the proper identification between different types of cybernetic model and real assemblies.
Conversely, cybernetics relies upon theories or mathematical tools that have been separately developed. Among the most notable of these are game theory, communication theory, information theory, either in the sense of selective statistical information, or in the broader sense involving semantic and pragmatic information. Finally, the theory of algorithms, the theory of control, set theory (q.v.), the theory of graphs, and linguistics make their contributions to this subject.
See also COMPUTER; GAMES, THEORY OF; INFORMATION PROCESSING; THINKING AND PROBLEM SOLVING.
Bibliography-W. R. Ashby, An Introduction to Cybernetics (1986); S. Beer, Cybernetics and Management (1959) ; L. von Bertalanffy and A. Rapport General Systems Yearbook, vol. i-xi, Society for General Systems Research, Ann Arbor, Mich. (1956-66) ; H. Von Foerster (ed.), Cybernetics: Proceedings of the 6th-l0th Conference (separate volumes; 1949-53); H. Von Foerster and G. Zopf, Jr. (eds.), Principles of Self-Organisation (1962) ; C. Gwinn (ed.), Cybernetic Problems in Bionics (1967) ; V. M. Glushkov, Introduction to Cybernetics (1966) ; J. Klir and M.Valach, Cybernetic Modelling (1969) ; W. S. McCulloch, Embodiments of Mind (1963); N. Wiener and J. P. Schade (eds.), Progress in Bioybernetics, vol. 1, 2, 3 (1964, 1965, 1966) ; N. Wiener, Cybernetics (1961) ; Proceedings of 1st-5th Congress, International Association for Cybernetics, Namur, Belg. (1956, 1955, 1961, 1964, 1967).