History of Cybernetics. Feedback and Servomechanisms

The publication of the book by Wiener gave name and status to the subject area, but earlier origins can be traced. At the time of the publication, the ideas also were promoted vigorously by Warren McCulloch, and the emergence of cybernetics has been attributed to the meeting and collaboration of Wiener with McCulloch and Walter Pitts.

McCulloch was a neurophysiologist who epitomized his own lifetime quest as the attempt to answer the question: ‘‘What is a number, that a man may know it, and a man, that he may know a number?’’ This question led him to study medicine and, particularly, neurophysiology. An interna­tional center for studies of what became known as cyber­netics was planned by him in the 1920s but had to be abandoned for financial reasons in the 1930s.

Before the meeting with McCulloch, a number of influences guided Wiener toward the initiative, a major one being his wartime work on the possibility of a predictor to extrapolate the curving path of an enemy aircraft so as to direct anti-aircraft gunfire more effectively. He had expo­sure to biological studies in a number of contexts, including introduction to electroencephalography by W. Grey Walter in the United Kingdom and work on heart muscle with the Mexican physiologist Rosenblueth; he also had learned about biological homeostasis in discussions with Walter Cannon. He also had been involved with analog and digital computing

The topic area, and its designation by name, were advanced greatly by a series of discussion meetings held in New York and sponsored by the Josiah Macy, Jr. Foundation between 1946 and 1953. Ten meetings took place, chaired by Warren McCulloch and with the participation of scientists from different specializations, especially bringing together biological and nonbiological sciences.

The first five meetings, which were not recorded in print, had various titles that referred to circular mechanisms and teleology. From the sixth meeting onward, the proceedings were edited by Heinz von Foerster and published. Wiener’s book had appeared in the meantime, and in honor of his contribution, the reports on the last five meetings were entitled: Cybernetics: Circular, Causal and Feedback Mechanisms in Biological and Social Systems.

Relevant developments were not confined, however, to the United States. In Britain, an informal group called the Ratio Club was founded in 1949 and developed many of the basic ideas of cybernetics at first independently of the American work, although links were formed later. It also is noteworthy that the book by Wiener was published in French before the appearance of the English version and gave rise to a Circle of Cybernetic Studies in Paris. The Ratio Club was considered to have served its purpose, and the transatlantic separation ended by a conference in the National Physical Laboratory in Teddington, United Kingdom in 1958.

Feedback and Servomechanisms. What has been termed circular causation is a central characteristic of living systems as well as of many modern artifacts. The flow of effect, or causation, is not linear from input to output but has loops or feedbacks. The system is sensitive to what it, itself, influences, and it regulates its influence so as to achieve a desired result.

Conscious mus­cular movement is an obvious example, where the actual movement is monitored by proprioceptors in joints and muscles and perhaps also visually and the force exerted by the muscles is regulated using this feedback so as to keep the movement close to what is wanted despite unknown weight to be lifted, friction, and inertia. The feedback that produces stability is negative feedback, which is to say that an excessive movement in the desired direction must cause diminution of muscular effort and conversely for insuffi­cient movement.

Servomechanisms are artificial devices that similarly use negative feedback. They featured strongly in wartime applications, such as control of aircraft gun turrets, but were known much earlier, examples being the steering engines of ships and Watt’s governor to regulate the speed of a steam engine. The use of the term ‘‘governor’’ here encouraged the later appellation of Wiener.

Negative feed­back also appears in a crude but effective form in the familiar ball-cock valve of the toilet cistern, which regulates inflow according to the sensed water level, and in thermo­stats in rooms, ovens, and refrigerators. Regulation of temperature and many other variables by feedback from sensors also is a vital feature of biological systems.

Servomechanisms are required to respond rapidly to disturbances and, at the same time, to give stable control without large overshoots or oscillation. The achievement of this stability where the environment includes inertia and elasticity and viscous friction depends on the mathematical methods of Wiener and others, including Bode and Nyquist.

One connection with biology noted by Wiener is that the tremors of a patient with Parkinson’s disease are similar to the operation of a maladjusted servo. Negative feedback also is applied in electronic amplification and allows high­fidelity audio reproduction despite the nonlinear charac­teristics of the active components, whether vacuum tubes or transistors; important mathematical theory has been developed in this context.