thinking can serve as a language for communicating about complexity
and interdependencies. To be fully conversant in any language,
you must gain some mastery of the vocabulary, especially the
phrases and idioms unique to that language. This glossary lists
many terms that may come in handy when you're faced with a systems
Anything that builds up or dwindles; for example, water in a
bathtub, savings in a bank account, inventory in a warehouse.
In modeling software, a stock is often used as a generic symbol
for accumulators. Also known as Stock or Level.
Combined with reinforcing loops, balancing processes form the
building blocks of dynamic systems. Balancing processes seek
equilibrium: They try to bring things to a desired state and
keep them there. They also limit and constrain change generated
by reinforcing processes. A balancing loop in a causal loop
diagram depicts a balancing process.
Balancing Process with Delay
A commonly occurring structure. When a balancing process
has a long delay, the usual response is to overcorrect. Overcorrection
leads to wild swings in behavior. Example: real estate cycles.
Behavior Over Time (BOT) Graph
One of the 10 tools of systems thinking. BOT graphs capture
the history or trend of one or more variables over time. By
sketching several variables on one graph, you can gain an explicit
understanding of how they interact over time. Also called Reference
Causal Loop Diagram (CLD) One of the 10 tools of systems
thinking. Causal loop diagrams capture how variables in a system
are interrelated. A CLD takes the form of a closed loop that
depicts cause-and-effect linkages.
A systems archetype. In a "Drifting Goals" scenario,
a gradual downward slide in performance goals goes unnoticed,
threatening the long-term future of the system or organization.
Example: lengthening delivery delays.
A systems archetype. In the "Escalation" archetype,
two parties compete for superiority in an arena. As one party's
actions put it ahead, the other party "retaliates"
by increasing its actions. The result is a continual ratcheting
up of activity on both sides. Examples: price battles, the Cold
The return of information about the status of a process. Example:
annual performance reviews return information to an employee
about the quality of his or her work.
Fixes That Fail
A systems archetype. In a "Fixes That Fail" situation,
a fix is applied to a problem and has immediate positive results.
However, the fix also has unforeseen long-term consequences
that eventually worsen the problem. Also known as "Fixes
The amount of change something undergoes during a particular
unit of time. Example: the amount of water that flows out of
a bathtub each minute, or the amount of interest earned in a
savings account each month. Also called a Rate.
Structures that can be generalized across many different settings
because the underlying relationships are fundamentally the same.
Systems archetypes are a class of generic structures.
Graphical Function Diagram (GFD)
One of the 10 tools of systems thinking. GFDs show how one variable,
such as delivery delays, interacts with another, such as sales,
by plotting the relationship between the two over the entire
range of relevant values. The resulting diagram is a concise
hypothesis of how the two variables interrelate. Also called
Growth and Underinvestment
A systems archetype. In this situation, resource investments
in a growing area are not made, owing to short-term pressures.
As growth begins to stall because of lack of resources, there
is less incentive for adding capacity, and growth slows even
One of the 10 tools of systems thinking. A learning laboratory
embeds a management flight simulator in a learning environment.
Groups of managers use a combination of systems thinking tools
to explore the dynamics of a particular system and inquire into
their own understanding of that system. Learning labs serve
as a manager's practice field.
An area where small change can yield large improvements in a
Limits to Success
A systems archetype. In a "Limits to Success"
scenario, a company or product line grows rapidly at first,
but eventually begins to slow or even decline. The reason is
that the system has hit some limitcapacity constraints,
resource limits, market saturation, etc.that
is inhibiting further growth. Also called "Limits to Growth."
Management Flight Simulator (MFS)
One of the 10 tools of systems thinking. Similar to a pilot's
flight simulator, an MFS allows managers to test the outcome
of different policies and decisions without "crashing and
burning" real companies. An MFS is based on a system dynamics
computer model that has been changed into an interactive decision-making
simulator through the use of a user interface.
Policy Structure Diagram
One of the 10 tools of systems thinking. Policy structure diagrams
are used to create a conceptual "map" of the decision-making
process that is embedded in an organization. It highlights the
factors that are weighed at each decision point.
See Behavior Over Time Graph.
Along with balancing loops, reinforcing loops form the building
blocks of dynamic systems. Reinforcing processes compound change
in one direction with even more change in that same direction.
As such, they generate both growth and collapse. A reinforcing
loop in a causal loop diagram depicts a reinforcing process.
Also known as vicious cycles or virtuous cycles.
Shifting the Burden
A systems archetype. In a "Shifting the Burden" situation,
a short-term solution is tried that successfully solves an ongoing
problem. As the solution is used over and over again, it takes
attention away from more fundamental, enduring solutions. Over
time, the ability to apply a fundamental solution may decrease,
resulting in more and more reliance on the symptomatic solution.
Examples: drug and alcohol dependency.
Shifting the Burden to the Intervener
A special case of the "Shifting the Burden" systems
archetype that occurs when an intervener is brought in to help
solve an ongoing problem. Over time, as the intervener successfully
handles the problem, the people within the system become less
capable of solving the problem themselves. They become even
more dependent on the intervener. Example: ongoing use of outside
One of the 10 tools of systems thinking. A computer model that
lets you map the relationships that are important to a problem
or an issue and then simulate the interaction of those variables
Draws out the accumulators and flows in a system, giving
an overview of the major structural elements that produce the
system's behavior. Also called flow diagram or accumulator/flow
One of the 10 tools of systems thinking. A structure-behavior
pair consists of a structural representation of a business issue,
using accumulators and flows, and the corresponding behavior
over time (BOT) graph for the issue being studied.
The manner in which a system's elements are organized or interrelated.
The structure of an organization, for example, could include
not only the organizational chart but also incentive systems,
information flows, and interpersonal interactions.
Success to the Successful
A systems archetype. In a "Success to the Successful"
situation, two activities compete for a common but limited resource.
The activity that is initially more successful is consistently
given more resources, allowing it to succeed even more. At the
same time, the activity that is initially less successful becomes
starved for resources and eventually dies out. Example: the
QWERTY layout of typewriter keyboards.
A field of study that includes a methodology for constructing
computer simulation models to achieve better understanding of
social and corporate systems. It draws on organizational studies,
behavioral decision theory, and engineering to provide a theoretical
and empirical base for structuring the relationships in complex
A group of interacting, interrelated, or interdependent
elements forming a complex whole. Almost always defined with
respect to a specific purpose within a larger system. Example:
An R&D department is a system that has a purpose in the
context of the larger organization.
One of the 10 tools of systems thinking. Systems archetypes
are the "classic stories" in systems thinkingcommon
patterns and structures that occur repeatedly in different settings.
A school of thought that focuses on recognizing the interconnections
between the parts of a system and synthesizing them into a unified
view of the whole.
See Graphical Function Diagram.
A tool used to identify systems archetypes. To use a template,
you fill in the blank variables in causal loop diagrams.
Tragedy of the Commons
A systems archetype. In a "Tragedy of the Commons"
scenario, a shared resource becomes overburdened as each person
in the system uses more and more of the resource for individual
gain. Eventually, the resource dwindles or is wiped out, resulting
in lower gains for everyone involved. Example: the Greenhouse
above glossary is a compilation of definitions from many sources,
Innovation Associates' and GKA's Introduction to Systems
The Fifth Discipline: The Art and Practice of the Learning
Organization, by Peter Senge
High Performance Systems' Academic User's Guide to
The American Heritage Dictionary and The Random House