Systems dynamics is a methodology for understanding complex systems and how objects in these systems interact with each other and change over time. Systems are a pervasive part of everything human beings do. They include social systems, environmental systems, engineering systems, biological systems, and many others.
The approach of systems dynamics is to focus on a system as whole instead of trying to break it down into smaller parts, as other disciplines do. The main focus is on feedback loops within the system. In a feedback loop, object A affects object B, and in turn object B affects object A through a chain of causes and effects. Instead of examining the link between A and B independently from the link between B and A in order to predict how the system will behave, system dynamicists study the system as a whole.
The relationships within systems can be extremely complex and difficult to understand, so systems dynamics uses computer modeling and simulations to understand behaviors and problems within a system. A dynamicist identifies a problem and develops a hypothesis to explain the cause of the problem. He or she then builds a computer simulation model of the system and tests the system to make sure that it reproduces behaviors observed in the real system. Solutions to the problem are then devised and tested, and those solutions are implemented in the real system.
Systems dynamics became a professional field in the 1950s with the work of Jay W. Forrester. The original applications were related to physical, biological, and engineering systems. For example, when applied to an engineering setting such as a chemical plant, systems dynamics involves conducting thorough studies of the stability and dynamic behaviors of chemical processes and their control. These behaviors are then simulated using computer models before plants are constructed.
Following this, applications of systems dynamics grew to include social systems such as political, economic, and managerial ones. Given the human aspect, these systems tend to be more complex than engineering systems, for example. In social systems, the sum of individual actions and objectives is not enough to explain what happens in the system. The structure of the system itself is also responsible for explaining system behavior. In social system applications, governmental laws and regulations or corporate policies, for example, are tested experimentally on the system as a whole, while dynamically modeling their long-term effects on the various objects of the system.
