Teaching Students About Systems Dynamics Thinking
Fantastic Primer on Systems Dynamics Thinking all readers should scroll to the bottom (i.e. the most important section).
What Is Systems Dynamics( via Systems Dynamics Society)
System dynamics is a methodology for studying and managing complex feedback systems, such as one finds in business and other social systems. In fact it has been used to address practically every sort of feedback system. While the word system has been applied to all sorts of situations, feedback is the differentiating descriptor here. Feedback refers to the situation of X affecting Y and Y in turn affecting X perhaps through a chain of causes and effects. One cannot study the link between X and Y and, independently, the link between Y and X and predict how the system will behave. Only the study of the whole system as a feedback system will lead to correct results.
The methodology:( via Systems Dynamics Society)
- Identifies a problem
- Develops a dynamic hypothesis explaining the cause of the problem
- Builds a computer simulation model of the system at the root of the problem
- Tests the model to be certain that it reproduces the behavior seen in the real world
- Devises and tests in the model alternative policies that alleviate the problem
- Implements this solution.
Clarity on Mental Models (Via Jay W. Forrester)
Mental models contain a vast wealth of information that is available no where else. Mental models contain information about the structure and policies in systems. By structure I mean the elements in a system and the connections between the elements—who has what information, who is connected to whom, and, what decisions are made and where. By policies I mean the rules that govern decision making—what factors influence decisions, what is a particular decision point trying to accomplish, and what goals are sought. At this detailed level of structure and policies, mental models are rich and reasonably reliable sources of information.
However, mental models have serious shortcomings. Partly, the weaknesses in mental models arise from incompleteness, and internal contradictions. But more serious is our mental inability to draw correct dynamic conclusions from the structural and policy information in our mental models.
System dynamics computer simulation goes a long way toward compensating for deficiencies in mental models. In model building, one must remedy incompleteness and internal contradictions before the system dynamics software will even allow simulation. After a logically complete model has been created, one can be certain that the computer is correctly simulating the system based on the assumptions that were incorporated in the model. It is in simulation, or determining consequences of the structural and policy assumptions, that mental models are unreliable, but computer models are completely dependable. Students should also realize that there are no possible proofs of the validity of any models, whether they are mental or computer models. Models are to be judged by their comparative usefulness. Assumptions about structure and policies should be compared with any available information. Computer simulation results should be compared with behavior in the real system being represented. Discrepancies lead to improving both mental and computer models.
System Dynamics (Via Jay W. Forrester)
In systems composed of many interacting feedback loops and long time delays, causes of an observed symptom may come from an entirely different part of the system and lie far back in time.
To make matters even more misleading, such systems present the kind of evidence that one has been conditioned to expect. There will be apparent causes that meet the test of being closely associated in time and in location. However, those apparent causes are usually coincident symptoms arising from the distant cause. People are thereby drawn to actions that are not relevant to the problem at hand.
Most Important Section: Long-Term vs Short-Term Goals (Via Jay Jay W. Forrester)
A fundamental conflict exists between short-term and long-term goals. Students should observe this conflict between the present and the future in system dynamics models and then relate the lessons to their own lives. Actions that yield immediate rewards almost always exact punishment in the long run, and vice versa. Quick gratification is the enemy of future well-being. It is hard to find exceptions where actions with an immediate reward do not extract a price in the more distant future.
A person who steals may benefit immediately, but usually suffers later. A person who works all night to finish an important task pays by being inefficient for the next several days. Taking mind-altering drugs may give an immediate sense of well being at the expense of future ill health or poverty. Borrowing on credit cards allows an immediate increase in standard of living but the consequence in the longer term is a lower standard of living while paying back the loan and interest. Under pressure from voters, the U.S. Congress is borrowing money to provide ever-increasing goodies to constituents, with the probable future consequence that government becomes insolvent and may not be able to provide basic public services. Over a much longer time horizon, improved public health and modern agriculture raised the standard of living and reduced death rates, resulting now in the threat of an unsustainable population explosion.
Conversely, accepting a short-term disadvantage can often yield rewards in the longer-term. For example, saving now, rather than spending all one’s income, can increase the future standard of living. A company that foregoes higher dividends and increased executive salaries can invest in research on new products and increase future income.