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TERMS: FEEDBACK Most people think about feedback and feedback loops in a very practical manner: how their heater or air conditioning units work. In a heater, if the temperature goes lower than a certain point, a circuit is activated and the heater is turned on. Once the temperature is above a certain point, the circuit is broken, and the heater is turned off. The same type of a feedback loop operates with an air conditioning unit, except the temperature trigger levels are reversed from a heating unit. This is technically known as a negative feedback loop. It is a very useful type of feedback, one that tends to keep a particular system in a state of equilibrium or balance. For our heaters and air conditioners, that state is a temperature range that we helpfully find comfortable. Negative feedback loops are used in a variety of situations, from audio amplifiers and speakers to airplane autopilot mechanisms. But there is another type of feedback that may be illustrated with an economics example. Sony was generally credited with having the superior videotape technology with its Beta format and was first to market. However, a larger number of companies came to support the competing VHS videotape format initially developed by JVC. Although the image was not as sharp as the Sony Beta, these decks were less expensive and had a longer playing time, and over time, more and more consumers came to purchase VHS tape decks. When movie videos began to be popular, more tapes were available in the rental stores in the VHS format (because more people had VHS decks), which in turn influenced more people to purchase VHS tape decks because there was more movie selection. This feedback loop of more people wanting VHS tapes leading to more VHS decks being sold continued for several years, and finally Sony ceased making Beta videotape machines altogether. The feedback loop described in the Sony example is technically known as positive feedback. As the example discusses, the output from one state of the system (the number of VHS tape decks and the number of videotapes) is fed back into the system, which then leads to more VHS tape decks and more VHS video tapes, which then lead to more VHS tape decks and more videos, and so on. Positive feedback loops are an important characteristic of many complex systems, and constitute one of the interaction processes that contribute to nonlinearities and emergence in complex systems. One of the challenges with understanding how complex systems function is to not confuse negative feedback which leads to the expected with positive feedback which often leads to the unexpected. |
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