Positive feedback

A positive feedback loop is a chain of cause-and-effect relationships that closes on itself to create a self-reinforcing change. It operates so that a change to any element anywhere in the loop will have consequences that cascade along the chain of causal links, finally changing the original element even more in the same direction. An increase will cause further increase; a decrease will cause further decrease (Meadows, D.H., et al, 2004: 25). The state of the system, such as one’s bank balance, grows continually larger as interest payments act as the rate of change. This is sometimes called a virtuous circle, as opposed to a vicious circle, which arises when the balance becomes negative and one gets deeper and deeper into debt as interest is added to the debt. Positive feedback is quite common in managed (economic) systems and may be valuable as an engine of growth. In an engineering system, however, positive feedback is undesirable and is designed out, which is one reason why the mathematical techniques of control engineering are of little help in designing managed systems. For a more detailed explanation of the feedback phenomenon, see Richardson (1991) and Coyle (1996). Also see negative feedback.