43 terms
Thinking in Systems
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holism/holistic thinking
process of understanding how things, regarded as systems, influence one another within a whole; in nature, systems thinking examples include ecosystems in which various elements such as air, water, movement, plants, and animals work together to survive or perish; in organizations, systems consist of people, structures, and processes that work together to make an organization "healthy" or "unhealthy"
system
interconnected set of elements that is coherently organized in a way that achieves something
system is more than the sum of its parts
it may exhibit adaptive, dynamic, goal-seeking, self-preserving and sometimes evolutionary behavior
interconnections
relationships that hold the elements together
many of interconnections in systems operate through the flow of information
information holds systems together and plays a great role in determining how they operate
least obvious part of the system
its function or purpose- often most crucial determinant of the system's behavior
most obvious part of the system
the elements- often least important in defining the unique characteristics of the system (unless changing an element changes its relationships or purpose)
stock
foundation of any system, elements of the system that you can feel, see, count, or measure at any given time; a store, quantity, accumulation of material or information that has built up over time; stocks don't always have to be physical; stock is memory of the history of changing flows within the system
flow
filling and draining, births and deaths, purchases and sales, growth and decay, deposits and withdrawals, successes and failures; stocks change over time through actions of a flow
dynamics of stocks and flows
their behavior over time
dynamic equilibrium
inflow is equal to outflow; level does not change
more than one way to increase a stock
a stock can be increased by decreasing its outflow rate as well as increasing its inflow rate
stocks act as delays or buffers or shock absorbers in systems
stocks generally change slowly, even when flows into or out of them change suddenly
stocks allow inflows and outflows to be decoupled and to be independent
stocks can temporarily be out of balance with each other
feedback loop
mechanism that creates consistent behavior- when stock grows by leaps and bounds or declines swiftly or is held within certain range no matter what else is going on around it; creates behavior persistent over long period of time; feedback loop created when changes in a stock affect the flows into or out of that same stock
feedback loop example
get your bank statement for checking account each month -- as level of available cash in checking account (stock) goes down you may decide to work more hours and earn more money -- money entering back account is flow that you can adjust in order to increase stock of cash to more desirable level -- bank account grows large and decide to work less (decreasing inflow) -- keeping level of cash available within range that is acceptable to you
balancing feedback loop (B)
equilibrating or goal-seeking structures in systems and are both sources of stability and sources of resistance to change; goal or stability seeking; opposes whatever direction of change is imposed on the system
reinforcing feedback loop (R)
self-enhancing, leading to exponential growth or to runaway collapses over time; found when a stock has the capacity to reinforce or reproduce itself
information delivered by feedback loop, even nonphysical feedback, can only affect future behavior
it can't deliver a signal fast enough to correct behavior that drove the current feedback, even nonphysical information takes time to feedback into the system
stock-maintaining balancing feedback loop must have its goal set appropriately to compensate for draining or inflowing processes that affect the stock
otherwise feedback process will fall short of or exceed target for the stock
shifting dominance of feedback loops
when one loop dominates another it has stronger impact on behavior; systems often have several competing feedback loops operating simultaneously and the loops that dominate system will determine behavior
dynamic systems not designed to predict that will happen
designed to explore what would happen if
model utility doesn't depend on whether its driving scenarios are realistic
depends on whether it responds with a realistic pattern of behavior
systems can produce similar dynamic behaviors
if they have similar feedback structures
system can oscillate
as result of delays in balancing feedback loop
delays
pervasive in systems and they are strong determinants of behavior; changing the length of a delay may (or may not depending on type of delay and relative length of other delays) make a large change in the behavior of a system
physical & exponentially growing systems require:
at least one reinforcing loop driving growth and at least one balancing loop constraining growth- no system can grow forever in finite environment
nonrenewable resources are stock-limited
entire stock is available at once and can be extracted at any rate (limited mainly by extraction capital) but since the stock is not renewed, the faster the extraction rate, the shorter the lifetime of the resource
renewable resources are flow-limited
they can support extraction or harvest indefinitely, but only at a finite flow rate equal to their regeneration rate; if they are extracted faster than they regenerate they may eventually be drive below critical threshold and come nonrenewable
resilience
ability to bounce or spring back into shape, position, etc. after being pressed or stretched; elasticity; ability to recover strength, spirits, good humor, or any other aspect quickly; measure of systems ability to survive and persist within variable environment; opposite is brittleness or rigidity; always limits to resilience
self-organization
capacity of a system to make its own structure more complex; ability of a system to structure themselves, to create new structure, to learn, diversify, and complexify
hierarchy
in process of creating new structures and increasing complexity, self-organizing system often generates hierarchy; organized into subsystems aggregated into larger subsystems, etc.; arrangement of systems and subsystems
suboptimization
resulting behavior when a subsystems goals dominate at the expense of the total systems goals
everything we think we know about the world is a model
our models do have a strong congruence with the world and our models fall far short of representing the real world fully
system structure is the source of system behavior
system behavior reveals itself as a series of events over time
linear relationship
between two elements in a system can be drawn on a graph with a straight line; relationship with constant proportions
nonlinear relationship
one in which the cause does not produce a proportional affect; relationship between cause and effect can only be drawn with curves or wiggles and not with a straight line
many relationships in systems are nonlinear
their relative strengths shift in disproportionate amounts as the stocks in the system shift; nonlinearities in feedback systems produce shifting dominance of loops and many complexities in system behavior
there are no separate systems
the world is a continuum; where to draw a boundary around a system depends on the purpose of the discussion- the questions we want to ask
limiting factor
bread will not rise without yeast no matter how much flour it has; children will not thrive without protein no matter how many carbohydrates they eat; at any given time the input that is most important to the system is the one that is most limiting; any physical entity with multiple inputs and outputs is surrounded by layers of limits
there will always be limits to growth
they can be self-imposed and if they aren't they will be system imposed
when there are long delays in feedback loops some sort of foresight is essential
to act only when a problem becomes obvious is to miss an important opportunity to solve the problem
bounded rationality
means that people make quite reasonable decisions based on the information they have but they don't have perfect information- especially about more distant parts of the system