Table of Con
Abstract: By recommending the infusion of system dynamics concepts into the
type of curriculum materials that educators currently seek, the “Trojan Horse
Strategy” aims to accelerate the rate at which the mainstream education system
adopts system dynamics. Drawing on principles from lesson plan development,
system dynamics, and application design, “Implementing the Trojan Horse
Strategy” describes process and techniques for helping teachers build student
understanding of subject matter and system dynamics simultaneously. This
practical guide for educators includes an overview of the strategy, an analysis of
the activities space within which these tools must operate, and a presentation of a
Implementing the Trojan Horse Strategy
Process and Techniques for Accelerating the Rate at which
System Dynamics Penetrates the Mainstream Education System
Peter M. Welles
High Performance Systems, Inc.
45 Lyme Road, Suite 300
Hanover, NH 03755 USA
Phone (603) 643-9636
Fax (603) 643-9502
pwelles@hps-inc.com
© 2002
four-step process for building educational tools that support the strategy.
has long been a shared vision for many in the system dynamics community; however,
progress toward achieving this objective has been slow. The slowness, in large part, is
because the effort that is currently underway stimulates opposing forces that serve to
directly counteract the effort. Constraints imposed by state and federal mandated teaching
agendas in conjunction with limited time available to achieve those objectives serve as
significant barriers to the spread of system dynamics knowledge. The successful spread
of system dynamics knowledge depends critically on the effective implementation of a
strategy that works in accordance with, not against, current cultural forces. By embedding
system dynamics inside types of educational lessons and tools that are currently accepted
by the mainstream education system, the rate at which the institution assumes a systems
perspective can be accelerated. Drawing on principles for effective lesson development,
The spread of system dynamics knowledge into the mainstream education system
Implementing the Trojan Horse Strategy
system dynamics, and application design, this paper lays out a process for creating tools
that support the strategy and presents examples of techniques from an actual tool
developed at High Performance Systems, Inc.
Limited teaching time, cultural values placed on discipline specific substantive
knowledge over discipline transcendent critical thinking skills, and the significant time
investment required to scale the number of system dynamics learning curves work
together to constrain the spread of system dynamics within the mainstream education
system. Given the current tools, the space available to teachers for teaching system
dynamics within their discipline specific curriculum is too limited to make any real
progress.
There may be, however, a way to increase the use of system dynamics by creating
a toolset that works in accordance with the current educational culture. Process and
techniques for creating these tools, however, depend on an understanding of both the
strategy these tools should support and the activities space, within which these tools must
operate.
The “Trojan Horse Strategy”! aims to accelerate the rate at which the mainstream
educational community takes up system dynamics by embedding system dynamics
concepts within the types of educational materials that teachers currently seek. As
teachers currently seek tools that communicate discipline specific subject matter,
effective tools would infuse system dynamics concepts into existing hard sciences, social
sciences, and humanities courses through educational resources that communicate subject
matter through system dynamics principles. Teachers, school boards, administrators,
students and parents would accept these sorts of tools because they would be consistent
with current cultural goals. Implemented skillfully, tools of this type would not only help
students build critical thinking skills on top of substantive knowledge, but due to the
benefits of applying a systems perspective, would simultaneously help deepen students’
subject matter understanding.
' The “Trojan Horse Strategy” was developed by Barry Richmond
Implementing the Trojan Horse Strategy 2
Process and Techniques
The process for creating tools that support the “Trojan Horse Strategy” draws on
techniques for effective lesson development, system dynamics, and application design.
Tools should support lessons that have all of the qualities of effective lessons. They
should support the current learning objectives, be developmentally appropriate for
students, etc. System dynamics knowledge plays a role in filtering subject matter for
content that is dynamically interesting and presenting that content operationally. If the
vehicle for delivering the lesson is computer software, basic application design principles
can help teachers deliver the content and build thinking skills effectively. The following
section is a description of process and techniques for developing effective tools,
particularly within an electronic medium.
Based on experience building software-based educational tools at High
Performance Systems, Inc. below is an outline of a process and examples of techniques
designed to help anyone who is interested in creating this type of tool. While the process
is presented linearly, in actuality, the process is iterative. Insights generated in one step of
the process often result in changes to decisions made in previous steps. There is,
however, a rough progression from the first step to the last.
Step 1: Select the Substance
In order to select the substantive knowledge to be communicated in a system dynamics
based lesson, filter the course topics using an understanding of dynamic concepts. Begin
with a topic, biology, for example. From the set of facts and concepts within this topic,
select processes that involve interesting dynamics. Processes should be described in terms
of behavior over time, stocks and flows, delays, and feedback loops. Dynamics that lead
to unintended consequences and results that are difficult to intuit are usually most
effective.
Example Within the topic biology, lessons about algae blooms, predator prey
interactions, and cellular respiration would be dynamically interesting. Lessons focused
on identifying the seven characteristics of life or understanding the classifications used by
taxonomists would probably not benefit from system dynamics.
Implementing the Trojan Horse Strategy 3
Step 2: Make Preliminary Learning Objectives Explicit
After the substance has been identified, establish the substantive and critical thinking
(including system dynamics) learning objectives. Clear and explicit objectives will help
focus the tool development process. Here is an example of the learning objectives from
one challenge in Food Chain, a product from High Performance Systems, Inc.
Biology/Environmental Science
1. Understand the interdependencies between the four trophic levels
in an ecosystem.
2. Understand the relationships governing births and deaths of
various plant and animal species within an ecosystem, and the
concept of steady-state (both how it’s achieved, and how it’s
maintained).
3. Understand O02, CO2 and nutrient dynamics within an ecosystem.
Critical Thinking Skills
1. Build capability in applying the scientific method, to include:
formulating and articulating hypotheses, designing experiments to
test those hypotheses, and analyzing experimental outcomes to
understand why results came out as they did.
2. Build capability in analyzing behavior-over-time graphs, using
trajectories to construct chains of cause-and-effect.
3. Build first-level fluency in the language of stocks and flows for
representing species and activities within an ecosystem.
4. Build capability for recognizing counteracting and reinforcing
feedback loops, and for understanding how these loops work.
5. Build an understanding for how shifts in dominance between
feedback loops can cause changes in dynamic behavior patterns.
6. Build a capability for recognizing and anticipating “unintended
consequences.”
As in any lesson development process, emphasis should be placed on developing clear
learning objectives. While filtering content for concepts that are dynamic is a good step
toward creating a lesson or tool, that step does not necessarily allow you to clearly
identify the dynamics. For example, the topic “algae bloom” might be selected for a
lesson, based on the understanding that excess nutrient runoff into a body of water often
leads to a bloom and subsequent collapse of the algae population. This overshoot and
collapse, as well as the associated impact on the ecosystem, plays out over time and has
historically resulted in devastating unintended consequences for those communities who
Implementing the Trojan Horse Strategy 4
have allowed nutrients to leach into the water. So the “algae bloom” topic would pass the
filter for dynamic processes, but without producing an explicit model, the relationships
may not be clearly and operationally defined. Having clear explicit assumptions about
relationships and behavior patterns is important for establishing effective learning
objectives, which will serve as the basis for the construction of the tool.
Creating a stock and flow model is a very effective way to identify the relevant
relationships operationally. Furthermore, the model building process often leads to
insights about the relationships and resulting dynamics. Stock and flow maps and
behavior over time graphs are other tools that help identify relationships and behavior
patterns. Whatever the means, clearly understood dynamics and relationships will better
facilitate the identification of learning objectives.
Step 3: Define the Learning Process
Defining the learning process implies choosing an approach or combination of
approaches that support the objectives. The learning process encompasses the learning
activities, as well as the infrastructure or materials that support the activities. As the two
are highly interdependent, the learning activities and the infrastructure that supports the
activities should be considered simultaneously.
Learning Activities
The activities space can be framed in terms of two fundamentally different
thinking processes: synthesis and analysis. Synthetic processes focus on combining
separate parts to form a whole, where analytic processes involve identifying distinct parts
from the whole.
Implementing the Trojan Horse Strategy 5
Degree of Synthetic Rigor ———»
Consumption Extension Construction
BOTGs
Behavior Over Time
Graphs
Students asked to con;
S/f map (could beAC map)
S/f Maps
Unintended ete) to capture son
Consequences Maps aspect of the reality.
Stu s asked to construct
S/f modeTagd perhaps also:
an interface, aMarytelli
sequence, a s-s initMization,
and/or a testing regimen.
S/f Models
<«— Joby onAjeuy jo vebaq —
NOTE: Degree of difficulty follows direction of arrows.
Figure 1 — The System Dynamics Activities Space’
Figure 1 describes activities along the synthetic continuum based on the amount of
intellectual rigor required to complete those types of tasks. Likewise activities along the
analytic continuum are organized based on the degree of analytic rigor. Examples of
activities that combine these two thought processes are stated inside the matrix.
In terms of difficulty of gaining the skills required to complete tasks, activities in
the lower right section of the graph are the most difficult, where activities in the upper
left are the least difficult. Furthermore, there is a great deal of difference in difficulty
between the two extremes. Activities that would fall into the upper left corner could be
completed successfully after one lesson, whereas many lessons would be required to
achieve proficiency at activities in the lower right section. This large discrepancy in
degree of difficulty has implications for the type of tools that should be constructed.
When considering the curricular space, activities that would be appropriate for students
who have not had prior experience with system dynamics would fall in the highlighted
regions in figure 1.
“The System Dynamics Activities Space” diagram, courtesy of Barry Richmond
Implementing the Trojan Horse Strategy 6
Challenge 3 from Food Chain serves as a good illustration of a progression of
learning activities and how they could be put together in a way that supports the learning
objectives (listed earlier) for an audience of students who have not had prior experience
with system dynamics. This particular progression involves overview, background,
exercises, and evaluation.
Food Chain is a software product designed for college and university introductory
level courses in Biology and Environmental Science, as well as high school level courses.
Students at each level experientially discover ecosystem dynamics through a simulated
open water lake ecosystem. Challenge 3 consists of four sections designed to set the
context and provide an overview for the challenge, provide background content
information about the components of the ecosystem, and allow the students to conduct
and analyze experiments.
Overview
The first section “Understand the Challenge” explains the context. A newspaper article
reads that “a lone dissenter on the Lake Mirabile zoning committee has held up a
proposal to construct 100 new houses on the shoreline of Lake Mirabile.” While the
committee realizes that more houses would mean a higher tax base and more spending
money for the community, they also realize that there may be potential environmental
implications of the construction. The student, an environmental scientist and long-term
member of the community, has been called upon to analyze the situation.
Background
The next section “Lake Mirabile” provides background information on the
components (species, carbon dioxide, oxygen, detritus and nutrients) of the ecosystem.
Implementing the Trojan Horse Strategy 7
Sunfish Facts
Location:
Native to the eastern half of the United
States
Physical Characteristics:
‘Between 3.5 and 60 cm in length
Nutrition:
Bat daphnia and copepods
Require:
Oxygen for respiration
Produce:
Carbon Dioxide
Figure 2 —- Background
Fact cards, such as the one in Figure 1, are used to provide the background content
information the students will need to complete the challenge, as well as develop
understanding of the lake ecosystem.
Exercises
In the third section “Develop Your Recommendation” students have the opportunity to
explore different housing construction scenarios in the simulated ecosystem. This is
where the system dynamics specific techniques come into play. System dynamics specific
teaching techniques, however, do not exist independently of other teaching techniques.
Food Chain, for example, uses student directed experiential learning in a way we term
“structured discovery,” as well as Socratic method techniques. As it is important to
incorporate systems dynamics concepts into discipline specific subject matter, it is also
important to integrate a systems dynamics approach into other teaching techniques.
The first scenario that students conduct is a base case scenario that shows what
would happen if no new houses were constructed. In this scenario, the ecosystem is in a
Implementing the Trojan Horse Strategy 8
state of equilibrium, so population levels for all species as well as quantities of nutrients,
detritus, carbon dioxide and oxygen, remain constant. While on the surface, this is not
particularly interesting, the experiment paves the way for a coaching sequence, which
highlights the difference between a static and active equilibrium.
Figure 3 —- Coaching Sequence
Coaching is a technique where a message or series of messages is displayed based
on simulation results or a decision a student has made. Some uses of coaching include...
1. highlighting or drawing attention to a specific simulation result that is
important to the understanding of the substance or dynamics of the lesson
2. explaining dynamics that have occurred in a simulation
3. inferring students’ mental models based on the decisions they have made and
capitalizing on “teachable moments” to broaden that mental model.
4. posing a pregnant question in an effort to guide the student in their thought
process
Implementing the Trojan Horse Strategy 9
This particular coaching sequence illustrates that any population experiences constant
reinforcing pressures, trying to push the population up, as well as constant counteracting
pressures, trying to pull population levels down. Furthermore, the strengths of these
pressures can shift due to changes in the ecosystem. The reason that the populations
remain constant when the ecosystem is in equilibrium is not because there are no
pressures acting on the population. It is because the reinforcing pressures are exactly
balanced by the counteracting pressures.
The dynamic concepts of reinforcing and counteracting loops are also introduced,
not just in broad terms of upward and downward pressures (though this is still useful), but
also using stock and flow examples.
LS x
The reproducing process is a good example
of a reinforcing loop because it has a
natural tendency to gain momentum. As
the sunfish population increases, more
sunfish exist that can give birth to even
| a _f more sunfish. As the population grows,
the pressure to grow builds with each
(Jeers eee] Sunfish subsequent generation.
The loop's momentum can be further
S ‘ enhanced when situations inside the
) >3 ecosystem become favorable (for example,
when food is abundant), causing the birth
Explain rate to climb.
Reinforcing Loop
Figure 4 — Reinforcing Loop Stock/Flow Example
At this point, students should probably not be subjected to the details of the
mathematical, statistical, or operational relationships between things like Sunfish, birth
rate, and reproducing. A focus on these details would likely obscure the understanding of
biology that the lesson should achieve. There is value, however, in building a high level
Implementing the Trojan Horse Strategy 10
understanding of the language, structural relationships, and dynamic concepts. Students
will be able to apply these high level concepts to build understanding. Furthermore, when
they come across stock and flow diagrams in the future (and they will in this tool!), the
language will be less foreign and easier to digest.
Students also explore a scenario that represents the opposite extreme from no new
construction: the construction of all 100 new houses. While this scenario also contains
coaching that is similar to the “no new houses” scenario, from the student’s perspective,
more focus must be placed on the analysis of behavior over time graphs to help determine
causality in a sequence of events. These events begin when nutrients from fertilizer and
septic systems runoff into the lake. Excess nutrients cause algae to bloom and overshoot
the carrying capacity of the ecosystem, ultimately resulting in the collapse of the algae
population. This collapse of the primary producer population, which is at the bottom of
the food chain, sets off a series of events that is highly disruptive to the ecosystem.
Figure 5 — Behavior Over Time Graphs
An important system dynamics skill is the ability to move beyond simple
immediate cause and effect relationships and think in terms of behavior over time.
Implementing the Trojan Horse Strategy 11
Thinking in terms of behavior over time is important because delays between cause and
effect often make effects difficult to intuit. Considering only the immediate consequences
of an initiative like the decision to construct houses on the shoreline of a lake often means
inadvertently engendering long-term losses with short-term gains. In the case of the
nutrient runoff and subsequent algae bloom, the species populations actually thrive
shortly after the bloom. If the zoning committee fails to consider the inevitable collapse
of the algae population, their decision would likely bring long term consequences for the
ecosystem and community. Relying on behavior over time graphs and asking students to
explain behavior over time is a good way to build these skills. By using behavior over
time graphs to extend a boundary out in time, teaching tools can help students develop a
richer understanding of an open water lake ecosystem in the process of building
important system dynamics skills.
Another tool students can use to build understanding is a simplified stock and
flow diagram. This type of diagram uses stocks and flows as a language to better
understand the structural relationships that give rise to the behavior over time (figure 6).
decomposers giving off COZ
C02 in
Lake
singhe camivores
siving off COZ
taking in CO? Total Herbivore O07 op Total
Biomass ‘Camivore Biomass
——=}31— 3
herbivores eating
ccamivores eating
taking in nutrients
02 to herbies
plants dying
herbivores dying
camivores dying
Nutrients Detritus
“decomposing
decomposers dying
Total Decomposer
Biomass
l
Lake rat
(02 to camivores
posers 02 in
02 generated
Figure 6 — Simplified Stock/Flow Diagram
Implementing the Trojan Horse Strategy 12
The diagram is simplified (in this case presented without converters and connectors)
because overloading the diagram with the less important elements of the language would
render it ineffective as a communication tool, especially when the audience is not yet
proficient with the language. In order to communicate effectively, isolate enough of the
essential components of the structure to represent the relevant relationships. Including
more than “just enough” is counter-productive.
While “what” you choose to present is important, “how” you present it is equally
important. One approach Food Chain uses is to begin with a blank screen and
progressively unfurl different segments of the diagram until the entire diagram is
displayed. It is easier to digest the diagram in pieces than try to swallow it whole.
Furthermore, each unfurled piece is accompanied by a text annotation that describes the
piece and its relationship to the rest of the system. Though the differences between stocks
and flows can also be described explicitly, this approach communicates the differences
between stocks and flows implicitly. Whether defined implicitly or explicitly, system
dynamics is used as a language to communicate relationships and achieve the discipline
specific learning objectives, as opposed to being the primary objective of the lesson.
Evaluation
Tools should support the “evaluation” objectives of a lesson. One way to do this is
through the approach used in Food Chain: to require students to write down and hand in
their responses to questions about the exercises.
Infrastructure
All of these learning activities rely on a materials infrastructure. In the case of this
specific tool, activities occur within the context of a software application architecture. For
software application based lessons, an architecture should be created that supports the
progression of activities. Applications consist of different “spaces” or screens. Each
screen allows access to other screens. The architecture, typically communicated in the
form of a diagram, shows what the screens are and how they connect.
Implementing the Trojan Horse Strategy 13
The Food Chain architecture is based on a combination of a menu and navigation
bar system. A full discussion of architecture design and the decisions leading to choices
for the Food Chain architecture is beyond the scope of this paper. Figure 8 is an example
of an architecture that should be useful for most small (lesson-sized) applications.
Background
| Back
Main Menu
1. Background
2. Exercise 1
3. Exercise 2 Exercise 1: Step 1 Exercise 1: Step 2
4. Conclusions Ny
Back Next 7—b) Back To Main Menu
r
i)
Figure 7 —- Sample Architecture Diagram
This sample architecture is organized around a main menu, which divides the application
into sections. Using a main menu screen provides an outline students can keep in their
mind’s eye while progressing through the application. This “outline” turns out to be
important because it gives students a framework for organizing their thoughts about what
they are doing in any section and how that fits into the overall activity. Students can
access a section by clicking on a button or link on the main menu screen that navigates
them to the first screen in the corresponding section. Within each section, they can then
use a “next-back” navigation scheme (where each screen has a “next” button and a
“back” button) to advance through a linear progression of screens. The last screen within
the section should have a link back to the main menu. While the “next-back” navigation
scheme does not provide the big picture outline of a section as the main menu navigation
Implementing the Trojan Horse Strategy 14
scheme does, it very clearly indicates what to do when a task is complete: click “next.”
This clarity works well when you want students to concentrate on the lesson’s material
and not on “where they are” or want to do next. This approach outlines a clear
chronology through the application as it helps students understand the overall
progression, as well as where they are within that progression.
Step 4: Evaluation and Feedback
An important part of any tool development process is testing the teaching tool to
determine its effectiveness. Software developers beta test their software before making
final fixes and releasing it. Good teachers test out their lessons in class or seek feedback
from colleagues, so that they can refine their methods. In an environment where few tools
exist and the road map for producing quality tools is still unclear, this step becomes even
more important.
Conclusion
A set of tools that use system dynamics concepts to communicate discipline
specific subject matter and build critical thinking skills would likely be adopted by the
mainstream education system at a faster rate than system dynamics concepts are currently
being adopted. This paper focuses on presenting process and techniques that can be used
for building a software application, designed to communicate system dynamics concepts
and substantive knowledge. While examples are from a specific tool, occupying a
fraction of the activities space, the process and techniques used should be transferable to
the development of other types of activities in other areas of the space. While the
universe of activities and effective design principles is only partially explored, the
approach and principles that have been identified seem to effectively communicate the
substantive and critical thinking lessons. Further exploration and successful
implementation means increasing the use of system dynamics within the mainstream
education system and consequently empowering the world to think and act more
Back to the T
Implementing the Trojan Horse Strategy 15
systemically.
