System dynamics II: feedback
Feedback is the second of our fundamental system dynamics concepts. It is hard to overstate its importance. Feedback loops play a dominant role in the behaviour of dynamical systems of all types and at all scales. As expressed by Richardson, in the quotation above, feedback loops are the deﬁning feature of system dynamics models, leading to the “endogenous point of view that is perhaps the single most characteristic and signiﬁcant feature of the ﬁeld”. A focus on endogenous forces, generated within the system boundary, is what gives system dynamics its ability to provide a fresh view of system behaviour and management (Richardson 2011). Yet, just as is the case for the concept of accumulation, feedback thinking is rare in human society (Richardson 1991: ix):
The seeds of this work were planted almost twenty years ago when I ﬁrst became aware of the feedback concept. I wondered then, and still ponder, how my education could have missed it. A powerful way of thinking-linking concepts of control and self-reinforcement, stability and instability, structure and behav - iour, mutual causality, interdependence, and uncounted numbers of the deepest ideas in the natural, social, and behavioural sciences-yet the concept was never mentioned in my undergraduate years.