An Introduction to System
Thinking
IE673
Session 3 - System Thinking
1
Contents
•
•
•
•
•
•
What is a system?
System Stability
Things in Common
Change and Growth
Putting the Pieces Together
Complex Systems
IE673
Session 3 - System Thinking
2
What is a System?
• Use “system” in everyday sense
• A collection of parts which interact with each other to
function as a whole
• A “heap” is not a system
• “Heaps” are not essentially change by adding or
subtracting from the “heap”
• A system can be part of larger systems
– subsystems form a hierarchy
IE673
Session 3 - System Thinking
3
Hierarchical System
•
•
•
•
•
•
•
•
•
Particle
Atom
Molecule
Cell Nucleus
Brain Cell
Brain
Nervous System
Individual
Local community
IE673
•
•
•
•
•
•
•
•
State
Nation
World Civilization
World Ecosystem
Planet Earth
Solar System
Galaxy
Universe
Session 3 - System Thinking
4
Systems and Stability
• If start at different point, still same results -- why?
• A system of smaller units is more stable
– Protons & neutrons - smallest natural particles
– Large atoms unstable - uranium
IE673
Session 3 - System Thinking
5
Systems and Stability (continued)
• Holds true for maximum size of animals
– Whales and dinosaurs
• A group of 5 versus 5000
• A large group is a mob unless higher levels of
system organizations are created
IE673
Session 3 - System Thinking
6
Systems and Stability (continued)
• Even if gigantic low-level systems were possible,
a series of higher level systems would be easier
– Millions of possible molecules
– 92 atoms
– 3 particles - protons, neutrons, electrons
IE673
Session 3 - System Thinking
7
Systems and Stability (continued)
• System definition key word - interact
• One part has effect on system - system has effect
on one part
– Circular relationship or loop
• Example - bicycle and rider
– A two part system
– Combined, can do things individual can not
– Constant small adjustment for “errors”
IE673
Session 3 - System Thinking
8
Systems and Stability
“Input”
Brain
Muscles
Bicycle
“Output”
Information
IE673
Session 3 - System Thinking
9
Systems and Stability
• Feedback loop
– Provides Stability
– Cancels out slight changes
– “Negative” feedback loop
• Negative feed back loops
– Occur by the thousands
– Are in our everyday life
IE673
Session 3 - System Thinking
10
Stability
• Negative feedback loops are everywhere
–
–
–
–
–
–
–
IE673
The thermostat
Body temperature
Float valves
Thirst
Inventories
Group membership
Predator and prey
Session 3 - System Thinking
11
Stability
• Systems can
– “Aim” at a fixed “target”
– “Track” a moving “target”
• Tracking systems
– Get feedback on how far it is from where it should be
– Uses the feedback to reduce the difference
IE673
Session 3 - System Thinking
12
Stability
• Tracking systems
–
–
–
–
–
–
IE673
Set-back thermostat
Radar-controlled anti-aircraft guns
Satellite docking systems
Sun tracking solar collectors
Driving a car
Riding a bicycle
Session 3 - System Thinking
13
Stability
• Tracking systems
– Human/Mechanical
• Person starts system going
• Guides with series of corrections
• System works so fast and so smoothly in some cases - hard to
believe there is time for negative feedback to work
• Common in natural and social systems
– Sunflower
– Politicians
– Companies
IE673
Session 3 - System Thinking
14
Things in Common
• Self-stabilizing systems make an active response
to change
– Bicycle
• An active response to change requires the use of
energy
– Wind generator
IE673
Session 3 - System Thinking
15
Active Systems
• Almost all living systems are active in sense that
they continue to function and use energy even
when dormant
– Must stay active when at rest or die
IE673
Session 3 - System Thinking
16
Active Systems
• General rule
– The more complex a system - the more energy spent on
maintenance
– Holds for social systems
• Isolated peasant community vs a modern community
IE673
Session 3 - System Thinking
17
Things in Common
• System limitations
– Amount and kind of change
• “Exposure”
• “Heat Stroke”
– Many negative feedback systems stable over wide
range, but fail abruptly when pushed beyond its limits
IE673
Session 3 - System Thinking
18
Things in Common
• Loose systems
– Negative feedback does not prevent change
– Negative feedback responds to change and keeps it
under control
– The result is a characteristic wobble - “sloppy”
IE673
Session 3 - System Thinking
19
Things in Common
• Reaction times
– Every negative feedback system has time limits
– Reaction time is most important
– The minimum amount of time necessary for one
complete circuit
– If too slow, fast change can damage system
IE673
Session 3 - System Thinking
20
Things in Common
• Anticipation
–
–
–
–
IE673
Sometimes can’t afford the delay
Systems cope - react to warnings
Need ability to interpret warnings
Inadequate reaction time due to responding to problems
rather than warnings
Session 3 - System Thinking
21
Things in Common
• Counter-intuitive systems
–
–
–
–
Behavior contrary to common sense
Predator - prey
High blood pressure
Rent control
• The “obvious” solution doesn’t work
– negative feedback loops fight direct intervention
– Change the way pieces interact
– Don’t try to “out-muscle” the system
IE673
Session 3 - System Thinking
22
Things in Common
• Hidden systems
– Hard to predict how system will react
– Feedback loops needed are not in sight
• African village
• 1929 tariff on imports
IE673
Session 3 - System Thinking
23
Things in Common
• Vulnerable systems
– Even the most stubborn system is vulnerable to
interference with information flow
• Slight breeze and bicycle
– Can be used to advantage to change way system acts
IE673
Session 3 - System Thinking
24
Change and Growth
• How?
– Negative feedback loop breakdown
– system becomes unstable and breaks down
– A different kind of feedback - positive
IE673
Session 3 - System Thinking
25
Change and Growth
• Negative feedback works to cancel out change
• Positive feedback works to cause more change
–
–
–
–
–
IE673
Sound amplifier - “squawk”
Interest on money
Living things
Knowledge
Power
Session 3 - System Thinking
26
Putting Things Together
• Plus and minus
– The organization of every complex system is built out
of the same two elements - positive and negative loops
– Can apply knowledge about one system to another
IE673
Session 3 - System Thinking
27
Putting Things Together
• Simple system - one of each type of loop
– Population growth
• Multiple loops
– Add factors that could affect the loops
IE673
Session 3 - System Thinking
28
Complex Systems
•
•
•
•
•
•
•
•
•
•
•
Characteristics
Self-stabilizing
Goal-seeking
Program-following
Self re-programming
Anticipatory
Environment modifying
Self-replication
Self-maintaining and repairing
Self-reorganizing
Self-programming
IE673
Session 3 - System Thinking
29
Complex Systems
• Problems of complexity
• The tragedy of the Commons
• Cost of information
– Rule of thumb
• Make each decision at the lowest possible level, but be ready
to shift the control of the situation to a higher level if a serious
problem occurs
• The distortion of feedback
• Loss of predictability (due to flexibility)
IE673
Session 3 - System Thinking
30