Feedback takes a part of a system’s output and applies it to change or to maintain its input. It is based on the actual rather than the potential or expected performance of the system. Feedback may be either negative (error correcting) or positive (trend enhancing). Positive feedback takes an increase in the output back to increase the input; negative feedback takes back an output to decrease the input - and is therefore stabilizing in principle. Positive feedback is wisely applied to encourage desired growth but must be kept under close surveillance to assure that explosive growth does not destabilize the whole. Negative feedback loops must be designed with appropriate time frames or uncontrolled oscillation will occur (called 'hunting' by control engineers). This may result in a 'correction' being applied in the wrong direction. This typically occurs in the management of economic policies because by the time the data are compiled the situation has often changed its trend. Feedback is essential to control. In a well functioning system, feedback loops are designed so that the system is brought back under control in the act of going out of control. The Watt steam governor is a good example of such a system. As the engine acquires speed the whirling balls move up, blocking the supply of air on which combustion depends. As the engine slows, the balls drop, increasing combustion by allowing more air to enter. Note: Feedback is sometimes mistakenly interpreted as simply a response, such as praise or criticism. Feedback was an early subject of study of the Conferences sponsored by the Josiah Macy Foundation in the 1940's and 1950's on the behavior of phenomena exhibiting circular causality. These Conferences brought together scientists from many disciplines and are credited with the launching of toe subject of study which was to become cybernetics. # SOURCE The term feedback probably was first used extensively in control engineering and in radio and electronics. # EXAMPLES • the message that the thermometer in a thermostat sends to signal the furnace to switch on or off (negative or error correcting) • the escalation of a disagreement into a conflict (positive or trend enhancing) • quality control inspections (negative) • the use of sales data in adjusting the production mix (positive or negative) • the self regulating mechanisms maintaining homeostasis (positive or negative) • the power steering on a car (positive) • biological specialization (positive or negative) # NON-EXAMPLES • canned laughter included in a television program • political poll taking when the constituency is unfamiliar with the candidates or the questions are stated in a biased manner • taking polls (or requesting other kinds of advice) as a fund raising device or when there is no means or intent to develop or modify a policy • market research among people who do not have a need for the product # PROBABLE ERROR • Using the wrong feedback loop to adjust an input • Sustaining feedbacks that actually have the wrong sign (as in practices that lead to war, divorce, etc.) # SEE Homeostasis; Cybernetics; Relaxation time; Self-organization