A system presents feedback when the behavior of interacting components of the system depend upon an interaction with neighboring components at an earlier time. We may divide feedback into two major types: positive and negative feedback. Negative feedback plays a role in maintaining homeostasis in more classically oriented systems theories. Positive feedback reinforces and amplifies existing system tendencies causing perturbations which can result in systemic collapse, or the emergence of new functions which the system did not originally manifest.
Complex systems and feedback
Complex systems may exhibit both postiive and negative feedback. Ladyman, Lambert, and Weisner (“What is a Complex System“, 2011) give the example of a flock of birds, which adjusts its group organization based upon how other members of the flight change the position of their individual flight patterns. They also note colonies of ants, in which the production of higher-order behavior and structuration, such as tunnel-building, appears as a result of the interaction of the various ants. Feedback may be a characteristic of a complex systems, but is not a sufficient characteristic of complexity, because it also requires a sufficiently large number of components for the behavior to arise. An ant left by itself, will not exhibit the behavior of a colony.