Demo Dozen

This collection of 13 dynamic models, constructed with the STELLA® (IseeSystems, Inc., Lebanon, NH 03766) modeling language, was originally designed to support educators and students as they explore the pedagogic value of System Dynamics in education. We find with experience that a much broader audience of users have profited from this collection.  Equally relevant for those with no previous modeling experience and for experienced modelers alike, this array of models demonstrates the potential breadth of systems-based curriculum.  A list of the Demo Dozen models (and links to more complete descriptions) is provided below.

As educators, we developed Demo Dozen as a tool to make learning about and using system dynamics (SD) both “fun” and meaningful. Challenging users to answer meaningful questions and manage real world systems using system dynamics-based computer simulations, we sought to utilize the power of experiential learning.  Ideally such an active learning approach fosters discovery of how decisions and actions can generate unexpected or non-intuitive behaviors more powerfully than being told what to do (or not to do) to effectively manage the system.

Challenging preconceptions (such as the mental models we all bring to such challenges) is a critical starting point for deepening learning.  Computer games can do that, but they need to offer more than an opportunity to find the “right” answer or to repeatedly manipulate model controls in an effort to “win” the game.  They also must provide a solid (perhaps a new) conceptual foundation upon which that learning experience can become more generalized and applied in other areas of interest.  Ideally – and here Demo Dozen seeks to distinguish itself from “black box” models and simulations – each unit’s “debrief” exposes the feedback thinking and structure within each model to stimulate interest in learning more about the mind- and tool-sets of system dynamics and SD’s value, as an educational tool, for transforming the way we think and act.

Please take the time to download these units, play with them, and most importantly, think about how the type of subject material presented in them, and/or the type of process illustrated by them, might be of use to you and of interest to your students. In addition, each model is accompanied by a relatively simple explanation of the logic and mechanics of its construction to give you a sense of what goes into building such simulations.

"Demo Dozen" is designed as a packet of models to illustrate the breadth of topics that can be productively explored with this approach to modeling, and, as well, to demonstrate how relatively simple simulations can be constructed and presented to support critical thinking on the part of both students and educators. Although there is a range of complexity represented in this collection of "relatively simple simulations," all should be readily understandable by folks with very brief introductions to system dynamics in general and to STELLA as a specific programming language.

Models in the "simple" folder could be built or modified by teachers and students after a relatively brief training experience; "complex" models could be built after a more complete introduction to modeling, such as provided by our “Modeling Systems Self-Taught” (MSST) tutorial or through a number of semester- or yearlong courses that have been developed by various high schools, colleges, and universities.

Topics within the “simple” folder include (in alphabetical order; links provide more complete descriptions):

 

• credit.stm: What are the tradeoffs in paying off a credit card debt, where debt grows through the wonders (and power) of compound interest in competition with your payments through one of three possible schemes?
• drgdose.stm:  ADDED FOR STELLA 8 AND STELLA 9 IN 2006.  How critical is the dose size and frequency in safely using Advil to meet your pain relief needs?
• inflatn.stm: How does a cost of living that is inflating (compounding) at one rate interact with a salary (inflating at a different rate) to influence the purchasing power you have?
• lilypad.stm: This simulation explores the power of exponential (compound) growth and the complexity of delays in managing a pond by asking the question: Can you successfully manage the growth of lily pads in a small pond?
• populat.stm: Can you predict the future implications of today's population growth rates for the United States and 2 developing nations?
• retire.stm: How will the power of compound interest, as you build a retirement nestegg, impact your comfort and financial security during your golden years?
• rumor.stm: How hard do you have to work to chase down and stop the compounding growth of that nasty rumor that's being spread about you?
• salad.stm: How long can you let the potato salad sit out in the warmth before the exponential growth of bacteria responsible for food poisoning renders it unsafe for human consumption?

 

Topics within the “complex” folder typically require modeling the interactions of two or more different processes. They include (in alphabetical order):

 

• andover.stm: How did the interaction of a growing population within the constraints of fixed local resources contribute to the growth of revolutionary fervor in small New England colonial towns?
• drugwar.stm: How well will pressure on the supply side of the cocaine trade, as the main policy option of the U.S. "War on Drugs," work to shut off the flow of this import?
• ireland.stm: How did the tragedy of the Irish Potato Famine contribute, over a period of decades, to the population dynamics of that country?
• kaibab.stm: How well could you have managed the resources of the Kaibab Plateau in the early 1900's in this computer simulation of a classic ecological case study?
• social.stm: Could you devise and implement a politically acceptable strategy to strengthen Social Security as a viable support for the retirement aspirations of today's US citizens?

 

Technical Requirements:

The models are written using STELLA9; STELLA8 will also open these, but earlier releases of STELLA will not (however, CIESD can provide copies of these materials written for the earlier STELLA6 or 7; please ask).

These models are designed for display resolutions of 1024 x 768 pixels or greater; a smaller-format version for STELLA8 or STELLA9 can be provided if needed (please ask). 

These models will run with IseePlayer that is available for free from the Isee Systems, Inc. website (http://www.iseesystems.com/softwares/player/iseeplayer.aspx). Regular versions of STELLA or iThink will also run these models.  Be aware, however, that I-think uses an “.itm” suffix in Windows environments; you may have to help these models find that software on your computer. If one of those versions is needed, please contact us.

 

Download:

Demo Dozen is provided here for free down-loading.